Evaluation of an immunoenzymatic test (ELISA) for the diagnosis of leptospirosis in Italy

Optimizing the microscopic agglutination test (MAT) panel for the diagnosis of Leptospirosis in a low resource, hyper-endemic setting with varied microgeographic variation in reactivity

The microscopic agglutination test (MAT) is the standard serological reference test for the diagnosis of leptospirosis, despite being a technically demanding and laborious procedure. The use of a locally optimised MAT panel is considered essential for proper performance and interpretation of results. This paper describes the procedure of selecting such an optimised panel for Sri Lanka, a country hyper-endemic for leptospirosis. MAT was performed using 24 strains on 1132 serum samples collected from patients presenting with acute undifferentiated fever. Of 24 strains, 15 were selected as the optimised panel, while only 11% of serum samples showed positivity. A geographical variation in predominantly reactive serovars was observed, whereas reactivity was low with the saprophytic strain Patoc. Testing with paired sera yielded a higher sensitivity but provided only a retrospective diagnosis. Serological tests based on ELISA with complementary molecular diagnosis using PCR are a feasible and robust alternative approach to diagnose leptospirosis in countries having a higher burden of the disease.

Seroprevalence and risk factor analysis of human leptospirosis in distinct climatic regions of Pakistan

Leptospirosis is a worldwide emerging infectious disease of zoonotic importance and large epidemics and epizootics have been reported all over the globe. A cross survey study was conducted to estimate seroprevalence of human leptospirosis in climatically distinct regions of Pakistan and to identify the risk factors associated with the disease. Blood samples from 360 humans were collected through convenient sampling, 120 from each of three study areas. Serological testing was performed using ELISA kit as per manufacturer's recommendations. The results showed an overall prevalence of 40.83% (95% CI; 35.71-46.11). Statistical analysis showed significant (P < .05) differences in leptospiral seroprevalence in three different geographic locations, with highest in humid sub-tropical climatic region (50.83%; 95% CI; 41.55-60.07), followed by semi-arid region (44.16%; 95% CI; 35.11-53.52) and lowest in hot and dry region (27.50%; 95% CI; 19.75-36.40). After multivariate analysis age, gender, exposure to flooding water, source of water usage, disinfection schedule of surroundings and history of cut and wound were found significantly associated with the seropositivity of Leptospira. The present study, first to uncover seroprevalence of human Leptospira in different climatic regions of Pakistan, alarms about effect of climate on prevalence of Leptospira in the region.

IgM ELISA for leptospirosis diagnosis: a systematic review and meta-analysis

Abstract A systematic review with meta-analysis was performed to estimate the accuracy of IgM ELISA for Leptospirosis diagnosis. A search of Medline, Lilacs, Embase, Cochrane Central Register of Controlled Trials and Grey literature (Google Scholar and British Library) was conducted. The medical subject headings (MeSHs) and the words “leptospirosis”, “human leptospirosis” and “IgM ELISA” were used. Fifty-two studies were analyzed, which included 10,775 samples. The pooled sensitivity of all the studies was 86% (CI 95%, 85%-87%) and specificity was 90% (CI 95%, 89%-91%). In studies of the acute phase, the sensitivity and specificity were 84% (CI 95%, 82%-85%) and 91% (CI 95%, 90%-91%), respectively. In conclusion, IgM ELISA is sensitive for use as an initial screen for leptospiral infections.

To evaluate the different rapid screening tests for diagnosis of leptospirosis

INTRODUCTION

Leptospirosis is an acute febrile disease, in tropical and sub-tropical regions of world. It has been under-reported in India, due to presence of non-specific symptoms and unavailability of appropriate laboratory diagnostic facilities in most part of the country. The diagnosis of leptospirosis is usually based on demonstration of antibodies by different serological tests.

AIM

The present study aims to evaluate and compare commercially available rapid test.

DESIGN AND SETTINGS

Case control study.

MATERIALS AND METHODS

Three screening tests (Leptocheck WB, Latex agglutination test and SD leptospira) were compared by using 100 serum samples randomly obtained from clinical cases of Leptospirosis admitted in new civil hospital, Surat, Gujarat. All the patients with acute Leptospirosis were included in this 4-months pilot study from July 2011 to October 2011. All the results were compared with IgM ELISA and MAT for confirmation of diagnosis.

RESULTS

Leptocheck WB, Latex agglutination test and SD leptospira had sensitivities of 84.8%, 84.8% and 72.7% & specificities of 37.3%, 71.2% and 71.2% respectively as compared to MAT. Leptocheck WB, Latex agglutination test and SD leptospira had sensitivities of 90.7%, 89.7% and 53.7% & specificities of 93.4%, 90.9% and 60% respectively as compared to IgM ELISA.

CONCLUSION

Latex agglutination test kit and Leptocheck WB were found to be highly sensitive and specific. Neither of these tests require specialized equipment, and could be performed in peripheral laboratories with relatively little expertise.

Evaluation of four commercially available rapid serologic tests for diagnosis of leptospirosis

Four rapid tests for the serologic diagnosis of leptospirosis were evaluated, and the performance of each was compared with that of the current standard, the microscopic agglutination test (MAT). The four rapid tests were a microplate immunoglobulin M (IgM)-enzyme-linked immunosorbent assay (ELISA), an indirect hemagglutination assay (IHA), an IgM dipstick assay (LDS), and an IgM dot-ELISA dipstick test (DST). A panel of 276 sera from 133 cases of leptospirosis from four different geographic locations was tested as well as 642 sera from normal individuals or individuals with other infectious or autoimmune diseases. Acute-phase sera from cases (n = 148) were collected <or=14 days (median = 6.0) after the onset of symptoms, and convalescent-phase sera (n = 128) were collected >or=15 days after onset (median = 29.1). By a traditional method (two-by-two contingency table), the sensitivities for detection of leptospirosis cases were 93.2% by LDS, 92.5% by DST, 86.5% by ELISA, and 79.0% by IHA. Specificity was 98.8% by DST, 97% by ELISA and MAT, 95.8% by IHA, and 89.6% by LDS. With a latent class analysis (LCA) model that included all the rapid tests and the clinical case definition, sensitivity was 95.5% by DST, 94.5% by LDS, 89.9% by ELISA, and 81.1% by IHA. The sensitivity and specificity estimated by the traditional methods were quite close to the LCA estimates. However, LCA allowed estimation of the sensitivity of the MAT (98.2%), which traditional methods do not allow. For acute-phase sera, sensitivity was 52.7% by LDS, 50.0% by DST, 48.7% by MAT and ELISA, and 38.5% by IHA. The sensitivity for convalescent-phase sera was 93.8% by MAT, 84.4% by DST, 83.6% by LDS, 75.0% by ELISA, and 67.2% by IHA. A good overall correlation with the MAT was obtained for each of the assays, with the highest concordance being with the DST (kappa value, 0.85; 95% confidence interval [CI], 0.8 to 0.90). The best correlation was between ELISA and DST (kappa value, 0.86; 95% CI, 0.81 to 0.91). False-positive LDS results were frequent (>or=20%) in sera from individuals with Epstein-Barr virus, human immunodeficiency virus, and periodontal disease and from healthy volunteers. The ease of use and significantly high sensitivity and specificity of DST and ELISA make these good choices for diagnostic testing.

Evaluation of a commercial enzyme-linked immunosorbent assay for detection of immunoglobulin M antibody in diagnosis of human leptospiral infection

The PanBio Leptospira immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) is a commercially available screening test for the diagnosis of acute leptospiral infection. The ability of the test to diagnose early or recent Leptospira interrogans infection was assessed by testing sera with known microagglutination test (MAT) titers to serovars pomona, hardjo, copenhageni, and australis. The IgM ELISA detected all 41 cases of early or recent leptospiral infection (sensitivity, 100%), with a positive ELISA result seen in many cases before MAT antibody titers reached 1:50. Thirty-eight of 41 patients showed seroconversion (fourfold or greater increase in titer by MAT, 2 of 41 patients had a single sample with elevated titer, and 1 patient from whom leptospires were isolated from a blood sample failed to show MAT titers, despite a seroconversion (negative to positive result) in the ELISA. Follow-up sera obtained from 8 of 12 patients (67%) for 3 to 48 months after the acute stage of illness showed persisting IgM antibody. However, the range of levels detected in these samples (maximum ELISA ratio, 2.0) was lower than the range seen when infection was recent. Reactivity in the IgM ELISA was observed for only 1 of 59 serum samples from asymptomatic donors (specificity, 98%) and 16 of 233 serum samples from patients with Ross River virus, brucella, Epstein-Barr virus, cytomegalovirus, mycoplasma, Q-fever, toxoplasma, hepatitis A virus, Treponema pallidum, or Borrelia burgdorferi infection (specificity, 93%), with the majority of these patients showing lower levels of IgM in comparison to those in patients with leptospiral infection. We conclude that this ELISA is sufficiently sensitive for use as an initial screen for leptospiral infections, with subsequent confirmation of positive test results by MAT.