title: Diagnosis of Leptospirosis: Comparison between Microscopic Agglutination Test, IgM-ELISA and IgM Rapid Immunochromatography Test.
abstract: BACKGROUND
  Leptospirosis is diagnosed on clinical grounds, and confirmed by microscopic agglutination test (MAT). IgM-ELISA (Serion-Virion) and immunochromatography test (Leptocheck-WB) are two immunodiagnostic assays for leptospirosis. Their sensitivity, specificity and applicability in Sri Lanka have not been systematically evaluated.
  
  
  METHODS
  Clinically diagnosed leptospirosis patients (n = 919) were recruited from three hospitals in the Western Province of Sri Lanka, during June 2012 to December 2013. MAT, IgM-ELISA and Leptocheck-WB were performed on all patient sera. MAT titer of ≥ 400 in single sample, four-fold rise or seroconversion ≥ 100 in paired samples were considered as positive for MAT. For diagnostic confirmation, MAT was performed during both acute and convalescent phases. Anti-leptospiral IgM ≥ 20 IU/ml and appearance of a band in the test window were considered as positive for IgM-ELISA and Leptocheck-WB test respectively. Patients with an alternative diagnosis (n = 31) were excluded. Data analysis was performed using two methods, i) considering MAT as reference standard and ii) using Bayesian latent class model analysis (BLCM) which considers each test as imperfect.
  
  
  RESULTS
  MAT, IgM-ELISA and Leptocheck-WB positivity were 39.8%, 45.8% and 38.7% respectively during the acute phase. Acute-phase MAT had specificity and sensitivity of 95.7% and 55.3% respectively, when compared to overall MAT positivity. IgM-ELISA and Leptocheck-WB had similar diagnostic sensitivity when compared with acute-phase MAT as the gold standard, although IgM-ELISA showed higher specificity (84.5%) than Leptocheck-WB (73.3%). BLCM analysis showed that IgM-ELISA and Leptocheck-WB had similar sensitivities (86.0% and 87.4%), while acute-phase MAT had the lowest sensitivity (77.4%). However, acute-phase MAT had high specificity (97.6%), while IgM-ELISA and Leptocheck-WB showed similar but lower specificity (84.5% and 82.9%).
  
  
  CONCLUSIONS
  Both IgM-ELISA and Leptocheck-WB shows similar sensitivities and specificities. IgM-ELISA may be superior to MAT during the acute phase and suitable for early diagnosis of leptospirosis. Leptocheck-WB is suitable as a rapid immunodiagnostic screening test for resource limited settings.
authors.affiliation: Institute of Biochemistry, Molecular Biology and Biotechnology, University of Colombo, Colombo, Sri Lanka.
authors.forename: Roshan
authors.initials: R
authors.lastname: Niloofa
authors.affiliation: Institute of Biochemistry, Molecular Biology and Biotechnology, University of Colombo, Colombo, Sri Lanka.
authors.forename: Narmada
authors.initials: N
authors.lastname: Fernando
authors.affiliation: Tropical Medicine Research Unit, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka.
authors.forename: Nipun Lakshitha
authors.initials: NL
authors.lastname: de Silva
authors.affiliation: National Reference Laboratory for Leptospira, Medical Research Institute, Colombo, Sri Lanka.
authors.forename: Lilani
authors.initials: L
authors.lastname: Karunanayake
authors.affiliation: Base Hospital Homagama, Homagama, Sri Lanka.
authors.forename: Hasith
authors.initials: H
authors.lastname: Wickramasinghe
authors.affiliation: Base Hospital Homagama, Homagama, Sri Lanka.
authors.forename: Nandana
authors.initials: N
authors.lastname: Dikmadugoda
authors.affiliation: Colombo North Teaching Hospital, Ragama, Sri Lanka.
authors.forename: Gayani
authors.initials: G
authors.lastname: Premawansa
authors.affiliation: Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka.
authors.forename: Rajitha
authors.initials: R
authors.lastname: Wickramasinghe
authors.affiliation: Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka.
authors.forename: H Janaka
authors.initials: HJ
authors.lastname: de Silva
authors.affiliation: Faculty of Science, University of Colombo, Colombo, Sri Lanka.
authors.forename: Sunil
authors.initials: S
authors.lastname: Premawansa
authors.affiliation: Tropical Medicine Research Unit, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka.
authors.forename: Senaka
authors.initials: S
authors.lastname: Rajapakse
authors.affiliation: Institute of Biochemistry, Molecular Biology and Biotechnology, University of Colombo, Colombo, Sri Lanka.
authors.forename: Shiroma
authors.initials: S
authors.lastname: Handunnetti
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000372:Agglutination Tests / Q000379:methods*; D000907:Antibodies, Bacterial / Q000032:analysis*; D002846:Chromatography, Affinity / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis*; D007919:Leptospira / Q000276:immunology; D007922:Leptospirosis / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D007075:Immunoglobulin M; D011933:Reagent Kits, Diagnostic