| Serology |
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African trypanosomiasis CATT Trypanosoma brucei gambiense Description Human african trypanosomiasis, known as “sleeping sickness”, is caused by the parasite Trypanosoma brucei. It is acquired through the feces of an infected tsetse fly and passes into the bloodstream to reach other blood fluids. T.b.gambiense is found in large areas of West and Central Africa. T.b.rhodesiense, on the other hand, causes East African sleeping sickness. The test procedure is an agglutination assay (CATT = Card Agglutination Test for Trypanosomiasis) that detects circulating antibodies against several surface antigens of T. b. gambiense of the infected host by direct agglutination. Interpretation 1) The CATT (Card Agglutination Test for Trypanosomiasis)-antigen is a freeze-dried suspension of purified, fixed and stained bloodstream form trypanosomes expressing a predominant variable antigen type of Trypanosoma brucei gambiense. 2) The sensitivity of the test is 87-98%. However, in acute cases of T. gambiense, it may take from 2 to 8 weeks to develop a detectable antibody titer. 3) The specificity of the test is 95% but cross-reactions with malaria and other parasitic diseases such as transient infection by non-human trypanosomes are observed. Spécificité/Specificity 95% Sensibilité/Sensitivity 87-98% American trypanosomiasis ELISA & Immunoblot Trypanosoma cruzi Description Chagas disease, or American trypanosomiasis, is acquired through contact with the feces of an infected triatomine bug (or “kissing bug”). Infection can also occur from mother-to-baby (congenital), contaminated blood products (transfusions) or an organ transplanted from an infected donor. Chagas disease is endemic throughout Mexico, Central America, and South America where an estimated 8 to 11 million people are infected. Blood smears are limited to the acute phase of infection, however, parasites are barely seen circulating in blood when there is low parasitemia. In the chronic phase, parasites are not found in circulating blood and the diagnosis of chronic Chagas disease in patients without immunosuppression should be performed with serology. The test procedure is an in-house indirect enzyme-linked immunosorbent (ELISA) assay for the detection of antibodies to Trypanosoma cruzi. An immunoblot assay is also available upon request for confirmatory testing. Interpretation (ELISA) 1) The antigen used in this test is a culture of Trypanosoma cruzi epimastigotes (Tulahuen and Brazil strains). 2) The sensitivity of the screening test (IgG-ELISA) is estimated at 100% for the indeterminate and chronic stage of the disease. 3) An OD ≥ 0.4 indicates T. cruzi infection at some unknown time. The sensitivity of the test varies with the infection. For chronic trypanosomiasis, sensitivity is good and negative serology is helpful in excluding the diagnosis. However, in acute cases of T. cruzi, it may take from 2 to 8 weeks to develop a detectable antibody titer. 4) The specificity (96%) of the test is good but cross-reactions with leishmaniosis, malaria and syphilis are observed. 5) If an equivocal result is obtained, a follow up specimen is required. Spécificité/Specificity 96% Sensibilité/Sensitivity 100% Interpretation (Immunoblot) 1. This test uses purified excreted-secreted antigens, derived from Trypanosoma cruzi trypomastigotes forms (TESA). 2. Sensitivity and specificity of the immunoblot confirmatory assay are estimated at 100% and 98 % respectively. Any polypeptide reactive band at 220, 170, 120, 85 and 60 kDa will be considered a positive result as described by Berrizbeitia et al. J Clin Microbiol. 2006;44(2):291-6. A positive reactive band at 60 kDa in a patient with definitive Leishmania infection may be cross-reactions, but concomitant occult T. cruzi infection in these individuals cannot be ruled. Disclaimer: This test is a laboratory-developed test that has not been approved or cleared by Health Canada. The result should be interpreted in conjunction with other clinical and laboratory findings. Spécificité/Specificity 98% Sensibilité/Sensitivity 100% Amebiasis ELISA Entamoeba histolytica Amoebiasis is acquired by ingesting cysts of Entamoeba histolytica in contaminated food, drinking water, or soiled hands. It is found throughout the world but is more prevalent in developing countries which lack sanitary facilities. Human infection results in several types of clinical conditions: a) asymptomatic carriers passing cysts whose infections are confined to the lumen of the intestine; b) patients with gastrointestinal symptoms with amoebic invasion of the intestinal mucosa; c) patients with extra-intestinal infection, usually liver abscess. Parasitological diagnosis of infection by stool examination should be performed, and is useful for detecting intestinal infections, but not extra-intestinal infection. Immunodiagnostic methods can provide serologic evidence of amoebic infection. The test procedure is an indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to E. histolytica. Interpretation (ELISA) 1) This test uses antigens of Entamoeba histolytica strain NIH-200. 2) The sensitivity of this test varies with the disease process such that 90-100% of individuals with extraintestinal amoebiasis are positive while only 70-80% of those with invasive disease limited to the intestine are positive. It is unclear if asymptomatic cyst passage without local invasion can ellicit a systemic IgG response. As a result, individuals infected with the non-invasive, but morphologically identical amoeba specie (Entamoeba dispar), would be expected to be negative. Although the reported specificity of this assay is high, only limited data are available using sera from individuals with diseases caused by other invasive amoeba species (eg. Acanthamoeba, Naegleria). 3) Significant antibody titers may take 10-14 days to develop even with documented invasive amoebiasis. Since positive titers may persist for many years after infection, a single test result must be interpreted with caution when prior infection is possible. 4) In some circumstances, it may be useful to determine the titers of anti-Entamoeba antibodies in paired specimens. Please contact the NRCP laboratory directly if this service is required. Spécificité/Specificity 100% Sensibilité/Sensitivity 92% Babesiasis IFA Babesia microti Babesiosis in North America is caused by the protozoan Babesia microti. It is transmited by the bite of infected ticks. Babesiosis can be co-transmitted with Anaplasma phagocytophila and/or Borrelia burgdorferi. Historically, diagnosis is made by the demonstration of characteristic intra-erythrocytic inclusions in thin smear preparations of peripheral blood. The IFA (immunofluorescence assay) test utilizes Babesia microti-infected erythrocytes as a source of characteristics inclusions for specific antibody detection. Interpretation: 1) This test uses antigens extracted from a human strain ofBabesia microti. 2) The sensitivity is evaluated at 100% for B. microti cases except for AIDS patients. The specificity is estimated at 99%. The antigens used appears to be very species specific, i.e. there is little cross-reactivity with other Babesia sp. However, cross-reactivity with Plasmodium sp is observed. 3) The serology could be very useful for diagnosis after parasitemia has cleared and for screening of asymptomatic individuals. 4) Titers of ≥1:64 are indicative of infection with B. microti. Titers may persist for 6 to 12 months after acute illness. A titer range between 1:64 and 1:256 suggests an infection of more than 6 months ago. A titer of 1:1024 indicates a relatively recent infection. Spécificité/Specificity 99% Sensibilité/Sensitivity 100% Baylisascariasis Immunoblot Baylisascaris Baylis ascaris infection is caused by a roundworm found in raccoons. This roundworm can infect people as well as a variety of other animals, including dogs. Human infections are rare, but can be severe if the parasites invade the eye (ocular larva migrans), organs (visceral larva migrans) or the brain (neural larva migrans). The test procedure is an in-house Immunoblot assay for the detection of antibodies to Baylis ascaris. Interpretation: 1) A recombinant protein is use for this Immunoblot, recombinant Baylisascaris procyonis RAG1 protein, derived from L3 stage of the parasite and purified from E.coli BL21 containing pRSET C/RAG1 plasmid. 2) Sensitivity and specificity of the screening test (Immunoblot) are estimated at 88% and 98%, respectively. Sensitivity of this assay may be higher but only a small number of ‘gold-standard’ positive sera have been available to test to date. There is no cross-reactivity with Toxocara infections. 3) Positives reactions should be supported with epidemiological evidence and/or exposure to raccoons or raccoon latrines. Spécificité/Specificity 98% Sensibilité/Sensitivity 88% Cysticercosis Immunoblot Taenia solium Cysticercosis, caused by the larval parasites of Taenia solium, is acquired by ingesting eggs from human feces or cysts from raw or poorly cooked infected pork. It is endemic in Mexico, Central and South America, Africa, India, and China. Patients with neurocysticercosis (when the larvae invades the central nervous system), often have seizures, increased intracranial pressure, and mental disorders. Brain scans (CT and MRI) can be very useful in demonstrating typical patterns of cysticerci but are not definitive diagnostic for single lesions. Parasitological diagnosis of infection requires biopsy of the cyst, often at great risk to the patient. Detection of cysticercosis-specific antibodies can provide useful evidence of infection. The test procedure is an immunoblot assay for the detection of antibodies to cysticercosis. Interpretation: 1) This test uses lentil-lectin, chromatography affinity-purified glycoprotein antigens derived from Taenia solium obtained from pigs. 2) Evaluation of the immunoblot assay indicated that sensitivity depends on the number and the vitality of the cysts. Sensitivity is estimated at 98% in biopsy proven cases of neurocysticercosis with 2 or more cysts. However, it decreases in cases with single enhancing or calcified cysts and varies from 28% to 72%. In patients with only subcutaneous cysts, sensitivity is below 50%. 3) The specificity of the test is evaluated at 100% and no cross-reactions are observed. 4) Both serum and cerebrospinal fluid (CSF) may be tested. Serum alone may be tested; however, due to the slightly decreased sensitivity of CSF, the latter should always be tested alongside a serum sample. Spécificité/Specificity 100% Sensibilité/Sensitivity 98% Echinococcosis ELISA Echinococcus species Echinococcosis (hydatidosis) is the infection caused by cestodes of the genus Echinococcus and is acquired by ingesting eggs passed in the feces of an infected animal. Hydatid cysts often develop in the liver, lung, spleen, and brain. The infection caused by Echinococcus granulosus is referred to as cystic hydatid disease (CHD). It is endemic worldwide and more frequently in rural, grazing areas where dogs ingest organs from infected animals. E. multilocularis is referred to as alveolar hydatid disease (AHD) and occurs in the northern hemisphere, including central Europe and the northern parts of Europe, Asia, and North America. Parasitological diagnosis of infection requires needle biopsy or excision of the cyst to demonstrate scoleces in the hydatid fluid of the cyst. The patient, however, is at great risk of experiencing an anaphylactic reaction when the cyst is breached. Immunodiagnostic methods can provide serologic evidence of echinococcal infection without disturbing the cyst. The test procedure is an indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to Echinococcus species. Interpretation: 1) This test uses Echinococcus granulosis cyst soluble antigens. 2) The sensitivity of this test is high but its specificity is relatively low with 10-15% false-positive results due to cross-reactions with a wide variety of helminth infections (e.g. Cysticercosis) and non-infectious conditions (e.g. cancer, pregnancy, autoimmune diseases). 3) Furthermore, the high sensitivity refers to long-standing hepatic disease alone. E. granulosus titers may be negative despite the presence of disease in several circumstances: small cysts (early after infection), intact cysts (no leakage of the immunogenic cyst fluid), cysts in extrahepatic locations or heavily calcified cysts (non-viable). 4) The results of this test should be interpreted with additional caution when an organism other than the classic E. granulosus is suspected on the basis of clinical or epidemiological information (eg. Arctic E. granulosus). 5) In some circumstances, it may be useful to determine the titers of Echinococcus antibodies in paired specimens. Please contact the NRCP laboratory directly if this service is required. Spécificité/Specificity 91.6% Sensibilité/Sensitivity 97.8% Fascioliasis ELISA Fasciola hepatica Fascioliasis, caused by Fasciola hepatica, is also commonly known as “the common liver fluke” or “the sheep liver fluke”. Fascioliasis is found in regions where sheep or cattle are reared. People usually become infected by eating raw watercress or other water plants contaminated with immature parasite larvae. Parasitological diagnosis involves stool examination under a microscope. However, infected people don’t start passing eggs during the acute phase of the infection. Even during the chronic phase of infection, it can be difficult to find eggs in stool specimen from people who have light infections. Serologic technique includes the detection of Fasciola hepatica-specific antibodies. The test procedure is an in-house indirect enzyme-linked immunosorbent assay for the detection of antibodies to Fasciola hepatica. Interpretation: 1) This test uses recombinant protein antigen FhCatL5 expressed from the pFLAG vector in Saccharomyces cerevisiae. 2) Sensitivity and specificity of the screening test (IgG-ELISA) are estimated at 100% and 96%, respectively. A positive reaction detected in a patient with definitive Trichinella or Toxocara infections may be observed. 3) If an equivocal result is obtained, a follow-up specimen is required. Spécificité/Specificity 96% Sensibilité/Sensitivity 100% Filariasis ELISA Brugia malayi Lymphatic filariasis, caused by microscopic, thread-like worms, affects over 120 million people in 80 countries throughout the tropics and sub-tropics of Asia, Africa, the Western Pacific, and parts of the Caribbean and South America. Damages to the lymph system, lymphedema, elephantiasis, or hydrocele may result from infection. Parasitological diagnosis of infection is made by the identification of microfilariae in a blood smear by microscopic examination. Serologic technique include the detection of Filaria-specific antibodies. Patients with active filarial infection have elevated levels of anti-filarial antibodies. The test procedure is an in-house indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to Brugia malayi. This assay could be used to investigate cutaneous findings (pruritis, nodules), eosinophilia, genitourinary findings (epididymitis, orchitis, hydrocele, chyluria), lumphangitis/lymphadema, and pulmonary infiltrates with eosinophilia syndrome. Interpretation: 1) This test uses antigens extracted from adult worms of Brugia malayi. 2) Sensitivity and specificity of the ELISA (IgG) are estimated at 91% and 84%, respectively. A positive reaction detected in a patient with definitive Schistosoma, Strongyloides or Echinoccocus infections may be due to cross-reactions. 3) An OD ≥ 0.3 indicates filaria infection at some unknown time and cannot be related to current infection. Anti-filaria antibodies may persist for years after infection; a single test result must be interpreted with caution when prior infection is possible. 4) This assay could be used to investigate cutaneous findings (pruritis, nodules), eosinophilia, genitourinary findings (epididymitis, orchitis, hydrocoele, chyluria), lymphangitis/lymphadema, and pulmonary infiltrates with eosinophilia syndrome. 5) If an equivocal result is obtained, a follow-up specimen is required. Spécificité/Specificity 84% Sensibilité/Sensitivity 91% Filariasis ICT Wuchereria bancrofti There are three different filarial species that can cause lymphatic filariasis in humans. Most of the infections worldwide are caused by Wuchereria bancrofti. Lymphatic filariasis affects over 120 million people in worldwide throughout the tropics and sub-tropics of Asia, Africa, the Western Pacific, and parts of the Caribbean and South America. The infection spreads from person to person by mosquito bites. The adult worm lives in the human lymph vessels, mates, and produces millions of microfilariae in the blood. They grow into adult worms, a process that takes 6 months or more. People with microfilariae can serve as a source of infection to others. This test is a rapid immunochromatographic test (ICT) for the qualitative detection of Wuchereria bancrofti antigen in whole blood, serum or plasma. Interpretation: The Filaria test is an in vitro immunochromatographic assay for the qualitative detection of Wuchereria bancrofti antigen in humans. It is intended to aid in the rapid diagnosis of lymphatic filariasis caused by W. bancrofti. It is recommended that negative test results be confirmed by standard diagnostic methods such as thick smear microscopy, membrane filtration, or another antigen detection method. Negative results do not preclude infection with W. bancrofti and should not be used as the sole basis for treatment or other management decisions. Spécificité/Specificity 93% Sensibilité/Sensitivity 99%[NL1] Gnathostomiasis ELISA Gnathostoma spp Gnathostomiasis is caused by a group of parasitic worms of the genus Gnathostoma. It is predominantly present in Southeast Asia, particularly in Thailand. However, infection in other parts of the world such as Central and South America, and Africa is increasing. Gnathostomiasis is acquired by eating undercooked and raw infected freshwater fish. Three to four weeks after ingestion of the parasite, when the parasite moves under the skin, people may experience swellings under the skin that may be painful, red, or itchy as well as high levels of eosinophils in the blood. The swelling can occur up to around 10 years after infection. Interpretation: 1) The Gnathostoma ELISA test is a semi-quantitative enzyme immunoassay using recombinant antigen for the detection of antibodies to Gnathostoma. 2) Diagnosis of Gnathostoma infection should not be made solely based on the results of the ELISA Gnathostoma test alone, but in conjunction with other clinical signs and symptoms and other laboratory findings. Epidemiologic factors, clinical findings, exposure to endemic regions, and other laboratory results should be considered when making a diagnosis. 3) The number of antibody positive subjects in a population depends on two factors: i) disease prevalence and ii) clinical criteria used to select the tested population. Because very few positives should be seen in a randomly screened population in a non-endemic area, most serology tests are not specific enough to screen non-endemic populations. Even in an endemic region, serology screening often yields many false positives if used to randomly screen patients. Serology tests are useful to test patients in an endemic region with signs and symptoms consistent with the disease. Spécificité/Specificity 100% Sensibilité/Sensitivity 93% Leishmaniasis DAT Leishmania donovani and L. infantum Leishmaniasis includes two major diseases, cutaneous leishmaniasis and visceral leishmaniasis, caused by more than 20 different leishmanial species. It is transmitted by the bite of the sandfly. Visceral leishmaniasis, caused by Leishmania donovani or L. infantum, is a severe systemic disease that is usually fatal without treatment. The distribution is worldwide, but 90% of cases occur in India, Bangladesh, Nepal, Sudan, Ethiopia and Brazil. This test is a direct agglutination test (DAT) that detects circulating antibodies against antigens of L. donovani or L. Infantum. Even before the onset of clinical symptoms, the direct agglutination assay is able to detect antibodies present in the blood or serum of the infected host. Interpretation: Infection with L.donovani or L.infantum, agents of visceral leishmaniasis, results in production of circulating antibodies against surface antigens of the parasite. Even before the onset of clinical symptoms, antibodies can be demonstrated in the blood or serum of the infected host by direct agglutination. The DAT/VL antigen is a freeze dried suspension of trypsin-treated, fixed and stained culture from promastigotes of L.donovani. The DAT/VL is intended for use at all levels of health services, from first-line screening of rural communities at risk to local reference laboratories for epidemiological studies including antibody titration Malaria ELISA Plasmodium falciparum, Plasmodium ovale, Plasmodium vivax, Plasmodium malariae, Plasmodium knowlesi Malaria is a parasitic disease caused by pathogenic agents of the genus Plasmodium. According to the World Health Organisation there are over 300 million malaria cases every year. The pathogen is found in many tropical and subtropical regions and can be transported by travellers to regions where it does not normally occur. The disease is mainly caused by P. falciparum, P. vivax, P. ovale, and P. malariae. Plasmodium falciparum, which survives in the blood, can be responsible for life-threatening relapses up to 2 years after the initial illness. The diagnosis of acute malaria is based on clinical symptoms and detection of the parasite in blood. Microscopic identification is the method of choice to demonstrate an active infection. Interpretation: 1) This test provides semiquantitative determination of human IgG for the serodiagnosis of Plasmodium ssp. It uses a mixture of recombinant antigen of all human pathogenic plasmodium species and detects antibodies againstP.falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi. 2) Serology should not be used for routine diagnosis. Diagnostic of acute malaria infections is based primarily on detection of the parasite in the blood by smear, antigen detection or nucleic acid amplification (PCR). 3) Positive titers only indicate malaria at some time in the past. Antibody titers may persist for years after therapy and without subsequent re-exposure. 4) Serology may be useful for identification of dormant infection, diagnosis of tropical splenomegaly syndrome and for screening blood donors. 5)Cross-reactivity with leishmania observed. Double infections must be taken into account, especially in endemic area. Spécificité/Specificity 96% Sensibilité/Sensitivity 99% Paragonimiasis ELISA Paragonimus westermani Paragonimiasis is caused by a trematode of the genus Paragonimus. The most common specie infecting humans is P. westermani, the oriental lung fluke, which occurs mainly in Asia. P. kellicotti is found in the midwestern and southern United States. The infection is transmitted by eating infected crab or crawfish that is raw, partially cooked, pickled or salted. Paragonimus infection can be serious if the fluke travels to the central nervous system, where it can cause symptoms of meningitis. The infection is usually diagnosed by identification of Paragonimus eggs in sputum but can only be detected 2-3 months after infection. Antibody tests also help differentiate between paragonimiasis and tuberculosis. Interpretation: 1) This test is a semi-quantitative ELISA that uses Paragonimus antigen. 2) In non-endemic population, results should be interpreted with caution and diagnosis of Paragonimus infection should not be made on results of the ELISA Paragonimus test alone, but in conjunction with other clinical signs and symptoms and other laboratory findings. 3) The number of antibody positive subjects in a population depends on two factors: i) disease prevalence and ii) clinical criteria used to select the test population. Because very few positives should be seen in a randomly screened population in a non-endemic area, most serology test are not specific enough to screen non-endemic populations. Even in an endemic region, serology screening often yields many false positives if used to randomly screen patients, Serology tests are useful to test patients in an endemic region with signs and symptoms consistent with the disease. Spécificité/Specificity 85% Sensibilité/Sensitivity 100% Schistosomiasis ELISA Schistosoma mansoni and S. haematobium Schistosomiasis, caused by parasites of the genus Schistosoma is estimated to infect over 200 million people in Africa, the Middle East, the Far East, and South America. Hepatosplenomegaly, liver disease, or bladder disease may result from Schistosoma infection. Parasitological diagnosis of infection is made by observation of eggs in stool, urine, or biopsy material. Detection of circulating antibodies in serum can also be useful for diagnostic. The test procedure is an in-house indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to Schistosoma mansoni and S. haematobium. Interpretation: 1) This test uses antigens extracted from adult worms of Schistosoma mansoni and S. haematobium. 2) Sensitivity and specificity of the ELISA (IgG) are estimated at 96% and 82 %, respectively. This assay could be used to investigate eosinophilia, abnormal liver function tests, dysentery, hematuria or fever and hepatosplenomegaly. A positive reaction detected in a patient with definitive Filaria, Taenia solium, Strongyloides or Echinoccocus infections may be due to cross-reactions. 3) An OD ≥ 0.4 indicates schistosome infection at some unknown time and cannot be related to worm burden, egg production, clinical status, or prognosis. Anti-Schistosoma antibodies may persist for many months after infection; a single test result must be interpreted with caution when prior infection is possible. 4) If an equivocal result is obtained, a follow-up specimen is required. 5) The performance of this test in individuals infected with related S. japonicum and S. megonki is not currently known. Spécificité/Specificity 82% Sensibilité/Sensitivity 96% Strongyloidiasis ELISA & Immunoblot Strongyloides stercoralis Symptoms of strongyloidiasis, caused by the parasite Strongyloides stercoralis, may include eosinophilia and diarrhea. Diagnosis and treatment of strongyloidiasis in the chronic intestinal phase are critical for preventing dissemination of the infection, which may prove lethal in immunosuppressed patients. Parasitological diagnosis of infection generally can be made by demonstration of larvae in stool, duodenal fluid, pleural fluid, or sputum. However, parasites may be difficult to find in some patients; detection of Strongyloides stercoralis-specific antibodies in serum may be a useful tool to indicate infection in such individuals. The test procedure is an in-house indirect enzyme-linked immunosorbent (ELISA) assay for the detection of antibodies to Strongyloides stercoralis. An immunoblot assay is also available upon request for confirmatory testing. Interpretation (ELISA): 1) This test uses recombinant protein antigen (NIE) derived from L3 stage of the parasite and purified from E.coli BL21 containing pET30b plasmid. 2) Sensitivity and specificity of the screening test (IgG-ELISA) are estimated at 100% and 88%, respectively. However, only a small number of ‘gold-standard’ positive sera have been tested to date. Sensitivity with the recombinant antigen might be lower in subjects with lower parasite burdens (ie: true positive but stool negative). A positive reaction detected in a patient with definitive hookworm, filaria, Schistosoma, Paragonimus or Echinoccocus infections may be cross-reactions, but concomitant occult Strongyloides infection in these individuals cannot be ruled out. 3) Only upon physician’s request, positive samples can be tested by immunoblot. This confirmatory assay shows a good specificity (98%) with a sensitivity of 100%. 4) If an equivocal result is obtained, a follow-up specimen is required. 5) Antibody levels decline to about 50% of initial titer 6 months after curative chemotherapy and generally become negative a year after therapy. Spécificité/Specificity 88% Sensibilité/Sensitivity 100% Interpretation (Immunoblot): 1) This test uses recombinant protein antigen (NIE) derived from L3 stage of the parasite and purified from E.coli BL21 containing pET30b plasmid. 2) Sensitivity and specificity of the immunoblot confirmatory assay are estimated at 100% and 98%, respectively. A positive reaction detected in a patient with definitive filaria infection may be cross-reactions, but concomitant occult Strongyloides infection in these individuals cannot be ruled out. 3) Antibody levels decline to about 50% of initial titer 6 months after curative chemotherapy and generally become negative a year after therapy. Spécificité/Specificity 98% Sensibilité/Sensitivity 100% Toxocariasis ELISA Toxocara canis Toxocariasis (larva migrans), is caused by the roundworm parasite Toxocara canis, and is acquired by ingestion of soil contaminated with embryonated eggs. Infection does not occur by contact with fresh feces; it takes 2-4 weeks for eggs to become infectious. Children with pica habits, as well as children in a household with a young pup, are at high risk for the disease. Symptoms of infection may include elevated eosinophil counts, fever, myalgias, hepatomegaly, rash, and ocular problems. Parasitological diagnosis of infection by demonstration of larvae in muscle tissue is very difficult so detection of Toxocara-specific antibodies in serum is the acceptable means of confirmation of infection. The test procedure is an indirect enzyme immunoassay (ELISA) for the detection of antibodies to Toxocara larvae. Interpretation: 1) This test uses excretory-secretory antigen derived from Toxocara larvae. 2) There is no « gold standard » test with which the performance of serologic assays for Toxocara can be compared. Furthermore, the titers obtained in individuals with clinical visceral larva migrans vary widely. The sensitivity and specificity estimates (above) apply to infections with T. canis. The performance of this test in individuals infected with related species (eg. T. leonis) is not currently known 3) The IgG response against Toxocara is likely to be proportional to the number of infecting larvae. 4) In some circumstances, it may be useful to determine the titer of anti-Toxocara antibodies in paired specimens. Please contact the NRCP laboratory directly if this service is required. Spécificité/Specificity 87.5% Sensibilité/Sensitivity 93.35 Toxoplasmosis ELFA Toxoplasma gondii Toxoplasmosis is caused by the parasite Toxoplasma gondii. The main source of infection is from Toxoplasma oocysts that are shed through an infected cat’s feces. Humans become infected by accidentally ingesting anything that has come into contact with Toxoplasma oocysts e.g. while cleaning a cat’s litter box. Toxoplasma can also be transmitted mother-to-child (congenital), whereby a newly infected woman may not show symptoms but there can be severe consequences for the unborn child, such as diseases of the nervous system and eyes. Organ transplant recipients can become infected by receiving an organ from a Toxoplasma-positive donor. The test procedure is an enzyme-linked immunofluorescent assay (ELFA) to detect antibodies against Toxoplasma gondii. It is offered as a CONFIRMATORY TEST ONLY for institutions outside of the province of Quebec. Previous serology results are required. VIDAS TOXO IgM / IgG II / IgG Avidity (bioMérieux) were used. Trichinosis ELISA Trichinella spiralis Trichinosis, caused by the parasite Trichinella spiralis, is acquired by ingestion of undercooked infected meat such as pork, wild game, and sea mammals. Symptoms of infection may include fever, myalgias, periorbital edema, conjunctivitis, vomiting or diarrhea, and elevated eosinophil counts. Parasitological diagnosis of infection by demonstration of larvae in muscle tissue is very difficult so detection of Trichinella-specific antibodies in serum is the acceptable means of confirmation of infection. The test procedure is an indirect enzyme immunoassay (ELISA) for the detection of antibodies to Trichinella larvae. Interpretation: 1) This test uses a purified excretory-secretory antigen produced by larvae obtained from pigs. 2) The sensitivity and specificity estimates (above) apply to infections with Trichinella spiralis. The performance of this test with other species (eg.Trichinella nativa) is not currently known. 3) The IgG response to T. spiralis infection tends to be slow and is proportional to the number of larvae ingested. Anti-Trichinella antibodies can be detected at 2 weeks in most individuals who have consumed a large number of cysts. Less heavily infected individuals may take up to 3-4 weeks to mount a detectable IgG response. Antibody titers peak 3-6 months after infection and then fall progressively even without treatment. Since low titers may persist for many years after infection, a single test result must be interpreted with caution when prior infection is possible. 4) In some circumstances, it may be useful to determine the titers of anti-Trichinella antibodies in paired specimens. Please contact the NRCP laboratory directly if this service is required. Spécificité/Specificity 93.8% Sensibilité/Sensitivity 85% |
| Polymerase Chain Reaction (PCR) |
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| African trypanosomiasis PCR Trypanosoma brucei Human african trypanosomiasis, known as “sleeping sickness”, is caused by the parasite Trypanosoma brucei. It is acquired through the feces of an infected tsetse fly and passes into the bloodstream to reach other blood fluids. T.b.gambiense is found in large areas of West and Central Africa. T.b.rhodesiense, on the other hand, causes East African sleeping sickness. Infection occurs in 3 stages. A trypanosomal chancre can develop on the site of inoculation. This is followed by a hemolymphatic stage with symptoms that include fever, lymphadenopathy, and pruritus. In the meningoencephalitic stage, invasion of the central nervous system can cause headaches, somnolence, abnormal behaviour, and loss of consciousness and coma. Parasitological diagnosis of infection requires microscopic examination of chancre fluid, lymph node aspirates, blood, bone marrow, or, in the late stages of infection, cerebrospinal fluid. Polymerase chain reaction (PCR) is used to amplify DNA from T. brucei parasites present in circulating blood or CSF. Interpretation: A DNA sequence situated at the 5% junction of the spliced leader sequence of the orphon element in Trypanosoma brucei is amplified using end-point polymerase chain reaction (PCR) using forward primer, T.brucei sensa (5’- GAT CCC TCT CCA CCA ATC GAC CG -3’) and reverse primer, T.brucei anti-sensa (5’- AAC TGC CCC GAC CTC CGC AGT -3’), as described by De almeida et al. Diagnostic evaluation of PCR on dried blood samples from goats experimentally infected with Trypanosoma brucei brucei. Acta Tropica. 1998 70:269-276. [NL2] American trypanosomiasis PCR Trypanosoma cruzi Chagas disease, or American trypanosomiasis, is acquired through contact with the feces of an infected triatomine bug (or “kissing bug”). Infection can also occur from mother-to-baby (congenital), contaminated blood products (transfusions) or an organ transplanted from an infected donor. Chagas disease is endemic throughout Mexico, Central America, and South America where an estimated 8 to 11 million people are infected. The most common diagnosis of Chagas disease is microscopic examination of blood smears. However, blood smears are limited to the acute phase of infection when parasites are seen circulating in blood. In the chronic phase, parasites are not found in the circulating blood and serologic testing is recommended. Polymerase chain reaction (PCR) is used to amplify T. cruzi-specific DNA in the acute phase of the infection or in re-activation of chronic Chagas disease due to immunosuppression. PCR can also be useful for early detection of T. cruzi in transplant-transmitted recipients of organs from donors with chronic Chagas disease. Interpretation:[NL3] The detection of Trypanosoma cruzi DNA by real-time PCR has proven to be a sensitive (90 %) and specific (100%, if Ct value ≤ 33) method for the diagnosis and monitoring of Chagas disease. As reported by Schijman et al. PLoS Negl Trop Dis. 2011 Jan 11;5(1):e931 and Ramirez et al. J Mol Diagn. 2015 Sep;17(5):605-15, standardized real-time PCR protocols targeting satellite nuclear DNA sequences allow for consistent detection of T. cruzi in blood samples. A negative real-time PCR result does not definitively exclude T. cruzi infection. In chronic Chagas disease, parasite loads may be very low and fluctuate below the detection limit of molecular assays. Therefore, negative results must be interpreted cautiously and in conjunction with clinical findings, epidemiological exposure history, and other diagnostic methods. Sensitivity of the test could increase to 100% during the acute phase. Disclaimer: This test is a laboratory-developed test that has not been approved or cleared by Health Canada. The result should be interpreted in conjunction with other clinical and laboratory findings. Spécificité/Specificity 100% Sensibilité/Sensitivity 90-100% Amebiasis PCR Entamoeba histolytica and E. dispar Amoebiasis, an infection affecting over 50 million people worldwide is transmitted by ingestion of contaminated water and food. Although amebic infection is caused worldwide, it is highly prevalent in Central and South America, Africa and in the Indian subcontinent. The pathogenic parasite causing this disease, Entamoeba histolytica is hard to distinguish from the non-pathogenic parasite Entamoeba dispar due to their morphological similarity. Thus, diagnosis requires highly sensitive molecular and enzymatic assays than microscopic examination. Polymerase chain reaction (PCR) allows the differentiation between these two species. Interpretation:[NL4] This qPCR assay targets the small subunit (SSU) 18S rRNA gene (amplicon size: 135 bp) to differentiate Entamoeba histolytica (pathogenic) from E. dispar (non-pathogenic). Molecular discrimination is crucial due to their identical morphology but distinct clinical relevance. Compared to ELISA and microscopy, the qPCR demonstrated higher sensitivity and specificity, particularly valuable in non-endemic settings for accurate treatment decisions, as described by (Gonin & Trudel, J Clin Microbiol 2003). Disclaimer: This test is a laboratory-developed test that has not been approved or cleared by Health Canada. The result should be interpreted in conjunction with other clinical and laboratory findings. Babesiasis PCR Babesia microti Babesiosis is caused by the parasite Babesia microti that infect red blood cells. Babesia microti is spread by the bite of an infected Ixodes scapularis ticks (also called blacklegged ticks or deer ticks). Tickborne transmission is most common in parts of the Northeast and upper Midwest of the United States especially in New England, New York state, New Jersey, Wisconsin, and Minnesota during warm months. Babesia infection can range in severity from asymptomatic to life threatening. Babesiosis can cause a hemolytic anemia, which can lead to jaundice and dark urine. The infection is both treatable and preventable. In symptomatic people, babesiosis is diagnosed by microscopy of red blood cells. It is also diagnosed by polymerase chain reaction (PCR), which has high sensitivity and specificity. Polymerase chain reaction (PCR) is used to amplify DNA from Babesia microti parasites present in blood. [NL5] Cysticercosis PCR Taenia solium Neurocysticercosis (NC), caused by the cestode parasite Taenia solium, is one of the most common parasitic diseases of the central nervous system (CNS). This disease is a major public health problem in Latin America, Africa, and Asia and has been diagnosed with increasing frequency in the United States. Most NC cases are asymptomatic. However, due to the high prevalence of CNS infection, symptomatic NC is also frequent. Symptomatic NC can range from a clinically mild to a severe, disabling disease, which includes seizures, intracranial hypertension, neurological deficits, and mental changes. Diagnosis is based on CT and magnetic resonance imaging (MRI). PCR, used to amplify DNA from Taenia solium parasites, is useful for the diagnosis of NC cases when imagery techniques are not available or have failed. Interpretation:[NL6] PCR is use to detect Neurocysticercosis. Primers are designed to amplify the highly repetitive element pTsol9 of the genome. This technique could be useful in cases where undetected infections could occur, under conditions of endemicity without apparent symptoms or when imagery techniques have failed, as described by Michelet et al. Human neurocysticercosis: comparison of different diagnostic tests using cerebrospinal fluid. J Clin Microbiol. 2012 Jan;50(1):212 Disclaimer: This test is a laboratory-developed test that has not been approved or cleared by Health Canada. The result should be interpreted in conjunction with other clinical and laboratory findings. Echinococcosis PCR: Echinococcus granulosus and E. multilocularis Cystic echinococcosis (CE) and alveolar echinococcosis (AE), caused by metacestode stages of Echinococcus granulosus and Echinococcus multilocularis, respectively, belong to the most serious helminth zoonotic diseases of humans. The diagnostic procedure for CE as well as for AE includes clinical, radiological and serological examinations carried out before (surgical) treatment. The definitive diagnosis is usually based on pathological–histological analysis of particularly periodic acid Schiff (PAS-) stained specimen of surgically resected tissues. However, Echinococcus cysts may be parasitologically sterile and contain neither protoscoleces nor rostellar hooklets, so that sometimes the pathologist is not able to differentiate between the two species E. granulosus and E. multilocularis. These strain differentiation is not possible using histological analysis and is only feasible by molecular methods such as PCR. Interpretation: This test is a multiplex real-time qPCR that detects and discriminates Echinococcus granulosus complex and Echinococcus multilocularis. The target sequences are located on a 471 bp segment of the mitochondrial ND1 gene as described by Schneider et al. International Journal of Parasitology 2008, 18: 1065-1071. The test’s performance characteristics are as follows: the assay demonstrates a specificity of 100% and a sensitivity of 90%. However, ongoing evaluation is necessary due to the limited number of samples tested so far. Disclaimer: This test is a laboratory-developed test that has not been approved or cleared by Health Canada. The result should be interpreted in conjunction with other clinical and laboratory findings. Spécificité/Specificity 100% Sensibilité/Sensitivity 90% Leishmaniasis PCR: Leishmania Pan – Genus detection Leishmania major, L.aethiopica, L.tropica (Old World leishmaniasis) Leishmania panamensis, L. braziliensis, L. mexicana, L. peruviana and L. guyanensis (New World leishmaniasis) Leishmaniasis includes two major diseases, cutaneous leishmaniasis and visceral leishmaniasis, caused by more than 20 different leishmanial species. It is transmitted by the bite of sand flies. Cutaneous leishmaniasis, the most common form of the disease, causes skin ulcers. Mucocutaneous leishmaniasis is a rare but severe form affecting the nasal and oral mucosa. Visceral leishmaniasis causes a severe systemic disease that is usually fatal without treatment. The distribution is world-wide, but 90% of visceral leishmaniasis cases occur in India, Bangladesh, Nepal, Sudan, Ethiopia and Brazil, while 90% of cutaneous leishmaniasis cases occur in Afghanistan, Algeria, Iran, Saudi Arabia and Syria (Old World leishmaniasis) as well as Brazil, Colombia, Peru and Bolivia (New World leishmaniasis). Leishmania Pan PCR assay uses polymerase chain reaction to amplify DNA from all species of Leishmania i.e. genus detection. Two additional PCR assays are offered for species differentiation between Old World and New World leishmaniasis. Malaria PCR Plasmodium falciparum, P. vivax, P. malariae, and P. ovale Malaria is transmitted among humans by the mosquito of the genus Anopheles. It is widespread in tropical and subtropical regions, including parts of the Americas, Asia and Africa. The disease is triggered by various species of the parasite Plasmodium. P. falciparum, P. vivax, P. ovale and P. malariae are of the greatest clinical significance. The most economic and common diagnosis of malaria is microscopic examination of blood smears. However, microscopic diagnosis can often be difficult, in particular with mixed infections, because early trophozoites (“ring form”) of all four species look identical. Polymerase chain reaction (PCR) is accurate in distinguishing between the species. Interpretation: This PCR is a Multiplex real-time qPCR for the detection of Plasmodium species. Primers are designed to amplify a highly conserved region of the 18S rRNA gene of Plasmodium, as described by Shokoples et al. J Clin Microbiol. 2009 Apr;47(4):975-80. The test’s performance characteristics are as follows: the assay demonstrates a specificity of 100% and a sensitivity of 100%. Disclaimer: This test is a laboratory-developed test that has not been approved or cleared by Health Canada. The result should be interpreted in conjunction with other clinical and laboratory findings. Spécificité/Specificity 100% Sensibilité/Sensitivity 100% Toxoplasmosis PCR Toxoplasma gondii Toxoplasmosis is a disease caused by the parasite Toxoplasma gondii, the definitive host for which is the felidae (domestic cats and their relatives) family. The disease is usually transmitted through ingestion of food contaminated with cat faeces, undercooked meat, transfusion from mother to fetus or rarely by organ transplantation and blood transfusions. The disease causes mild flu-like symtoms or no symptoms at all in healthy adults. However, it can cause serious illness in immunocompromised patients and pregnant women. Diagnosis commonly involves serological assays, molecular methods like polymerase chain reaction (PCR) and to a lesser extent direct microscopic examination. Polymerase chain reaction (PCR) is used to amplify DNA from T. gondii parasites present in body fluid. Interpretation: This PCR is real-time qPCR for the detection of Toxoplasma gondii. Primers are designed to amplify a highly conserved repetitive B1 gene of T. gondii, as described by Bretagne et al. J Infect Dis. 1993, 168:1585-8. The test’s performance characteristics are as follows: the assay demonstrates a specificity of 100% and a sensitivity of 99%. Disclaimer: This test is a laboratory-developed test that has not been approved or cleared by Health Canada. The result should be interpreted in conjunction with other clinical and laboratory findings. Spécificité/Specificity 100% Sensibilité/Sensitivity 99% |
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| Cryptosporidium Lateral Flow Cryptosporidium parvum Cryptosporidiosis is one of the most common waterborne diseases. The main symptom in immunocompetent individuals is a self-limiting short term watery diarrhea with symptoms lasting an average one week. The very young, old and the immunocompromised patients may develop more severe cryptosporidiosis. Infection occurs by the fecal-oral route via water, soil or food that has been contaminated with feces of an infected individual or animal. The test is a single use rapid immunoassay for the qualitative detection of Cryptosporidium parvum antigens in human stool specimens. It is intended for use with patients with gastrointestinal symptoms as an aid in the diagnosis of suspected Cryptosporidium gastrointestinal infections. Results should be considered in conjunction with the clinical evaluation and medical history. Giardiasis Lateral Flow Giardia lamblia G. lamblia cysts are excreted through the human colon into the environment. They are relatively resistant to chlorination and ozonolysis explaining why it is the most common cause of outbreaks of diarrheal illness due to drinking water. Giardiasis is also one of the leading causes of food and waterborne diarrhea throughout the world. Individuals contract Giardiasis by consuming contaminated food and water containing the Giardia cyst. Some symptoms associated with Giardiasis include but are not limited to diarrhea, malaise, flatulence, foul-smelling greasy stool, and abdominal cramps. Infections can last from several days or several weeks if left untreated. This test is a single use rapid immunoassay for the qualitative detection of Giardia lamblia antigens in human stool specimens. It is intended for use with patients with gastrointestinal symptoms as an aid in the diagnosis of suspected Giardia gastrointestinal infections. Results should be considered in conjunction with the clinical evaluation and medical history. Leishmaniasis Culture Cutaneous leishmaniasis Leishmaniasis includes two major diseases, cutaneous leishmaniasis and visceral leishmaniasis, caused by more than 20 different leishmanial species. It is transmitted by the bite of sand flies. Cutaneous leishmaniasis, the most common form of the disease, causes skin ulcers. Mucocutaneous leishmaniasis is a rare but severe form affecting the nasal and oral mucosa. In this test, biopsies/lesion scrapings/aspirates are cultured in an in-house growth medium and monitored over the course of 3 weeks for signs of Leishmania parasites. Specimen must be sampled, kept and sent at room temperature. |