POCT in parasitology. .pptx

POCT in parasitology. .pptx

• 1.
  Point Of CareTesting in Parasitology
• 2.
  Introduction to POCT •Defined as clinical laboratory testing conducted close to the site of patient care where care or treatment is provided. • An ideal POCT - defined by ASSURED criteria 1. Affordable 2. Sensitive 3. Specific 4. User friendly 5. Rapid 6. Robust 7. Equipment-free 8. Deliverable to end users or near patient care areas
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  • Why thereis a need of Point of Care Testing ? 1. An accurate rapid diagnosis of infectious diseases prompt treatment of the individual 2. Protect the community from exponential spread of the disease 3. Provides economical large scale screening programs • Limitation of the conventional techniques 1. Time consuming 2. Resource intensive 3. Requirement of highly trained lab staff
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  • First generationPOCT 1. Enzyme linked immunosorbent assays 2. Radio immunoassays • Second generation POCT 1. Lateral flow immunoassays (LFIA) • Third generation POCT 1. Molecular assays
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  Entamoeba histolytica • Arapid membrane enzyme immunoassay -- Quik Chek (commercially available as) • Qualitative detection and differentiation of entamoeba histolytica from nonpathogenic entamoeba dispar • Target ---- entamoeba histolytica adherence lectin • Time – 30mins • Specificity > 99% • Sensitivity < 50%, https://www.techlab.com/diagnostics/parasitology-diagnostics/entamoeba-histolytica-2/e-histolytica-quik-chek/
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  • The TriageMicro Parasite Panel (Triage) is the first immunoassay to simultaneously test stool for antigens from three common pathogenic protozoan parasites, namely, G. lamblia, E. histolytica/Entamoeba dispar, and C. parvum. • Antigens from clinical specimens that are specific for these three parasites are isolated and immobilized on a membrane using specific antibodies. An antibody-enzyme conjugate then binds to specific sites on these antigens. • Sensitivity 96% to 100% • Specificity --- 99% - 100% for detection of all three parasites • For extraintestinal amebiasis-- commercially available rapid POCTs have not been developed Fig : Triage parasite panel demonstrating positive results. (A) Positive and negative controls and positive test zone for G. lamblia (GIARD); (B) positive and negative controls and positive test zone for E. histolytica / E. dispar (E. HIST); (C) right, positive and negative controls and positive test zone for C. parvum (CRYPT).
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  • Malaria • MalariaRapid Diagnostic Tests (RDT) detect specific antigens produced by malaria parasites in the blood of the infected individuals. • RDTs are lateral flow immuno-chromatographic antigen-detection tests, which rely on the capture of dye-labelled antibodies to produce a visible band on a strip of nitro-cellulose enclosed in cassettes • The dye-labelled antibody first binds to a parasite antigen complex is captured on the strip by a band of bound antibody, forming a visible line (T - test line) in the results window. WHO Global Malaria Programme (GMP)
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  RDTs detect antigensincluding the histidine-rich protein II (HRP-II), aldolase, and parasite lactate dehydrogenase (pLDH). Commercially available kits for HRP-II detect P. falciparum HRP-II only and therefore diagnose only P. falciparum malaria. Parasite lactate dehydrogenase (pLDH) is produced by asexual and sexual stages (gametocytes) of malaria parasites. Test kits that are currently available detect pLDH from all four species of Plasmodium. They can distinguish P. falciparum from the non-falciparum species, but cannot distinguish between P. malariae, P. ovale, and P. vivax. Aldolase is produced by all species, so it is used as a pan-malarial marker Limitations of these RDTs 1. Sensitivity is very less if the density of parasite is less than 200/microliter 2. Unreliability in detecting infections with Plasmodium ovale and P. malariae 3. Also HRP-2 based RDTs cannot distinguish current from the recently treated infections as HRP2 remains positive for several weeks. BinaxNOW® Malaria Test, the only available RDT for malaria in the United States. www.cdc.gov/parasites/
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  • Molecular testbased on loop-mediated isothermal amplification (LAMP) technique • Simple, rapid, sensitive, and specific test and thus has become very popular as a point-of-care test for malaria • Commercially marketed as loopamp kit • Sensitivity 84- 95% in the diagnosis and 100% differentiation of non-falciparum species
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  Gazelle • Based onmagneto-optical detection of haemozoin crystals which is produced by all species from blood samples in < 1 min. • A beam of polarised light is passed through the lysed diluted blood sample under the influence of high and low magnetic fields. The difference in light transmission through the sample between the high and low magnetic fields indicates presence of haemozoin crystal suggesting possible malarial infection.
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  • Sensitivity andspecificity of this test is around 97% and 98% • Drawback - inability to differentiate various species of malarial parasite • Urine Malaria Test™ (UMT) dipstick test • detects P. falciparum Histidine-Rich Protein 2 (PfHRP2) in urine sample • sensitivity 83.8% and specificity of 83.48% • alternative option to more invasive methods especially where repeated sampling is required
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  • Leishmaniasis • Lateralflow immunoassay for the qualitative detection of antibodies including IgG and IgM • ICTs with rk39 antigen give results immediately within 20 min • Drawbacks : cannot be used to diagnose VL in immunocompromised patients and false positive results are higher in individuals from endemic area • Sensitivity - 93% to 100% • Specificity - 93% to 97% • CL detect rapid test -- POCT for cutaneous leishmaniasis • Qualitative, membrane-based test for the detection of antigen in amastigotes from skin lesions. • Sensitivity – 95% • Drawback - cannot be done on serum samples so while collecting the skin sample if blood is present it can interfere with the performance of the test
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  • Filariasis • Rapiddiagnostic tests used for diagnosing LF usually detects circulating filarial antigen of Wuchereria bancrofti • RDTs available : 1. Binax NOW filariasis immunochromatographic card test (ICT) 2. Alere filariasis test strip (FTS) • Rapid diagnostic tool used for the qualitative detection of Wuchereria bancrofti antigen in human blood samples collected by fingerstick. • More sensitive, and less expensive than the ICT. • The global program to eliminate LF relies on point of care rapid diagnostic tests to map regions endemic for LF and to determine when regions have successfully eliminated the disease
• 15.
  • Schistosomiasis • Therapid tests available for schistosomiasis detects circulating cathodic antigen (CCA) which is excreted in urine by live parasites during early infection. • The ICT based test detects CCA either in urine or serum but is not reliable for all species • These tests can be used in addition to conventional tests but lacks the sensitivity to be used as standalone diagnostic tool • Hydatid disease • A rapid tests in ICT format for the qualitative detection of total antibodies against Echinococcus granulosus antigen in both the serum and the plasma. It can give results in 30 min • >90% sensitivity and >95% specificity