Diagnostic accuracy of an IgM enzyme-linked immunosorbent assay and comparison with 2 polymerase chain reactions for early diagnosis of human leptospirosis.

Enzyme-linked immunosorbent assay (ELISA) tests and polymerase chain reaction (PCR) may play a key role for early detection and treatment of human leptospirosis in developing countries. The aims of this study were to develop and validate an IgM ELISA under field conditions and to compare the diagnostic accuracy among IgG, IgM ELISAs, conventional PCR (cPCR), and real-time PCR (rtPCR) for early detection of human leptospirosis. Overall accuracy of IgM ELISA was sensitivity of 87.9%, specificity of 97.0%, and area under the curve of 0.940. When the 4 methods were compared, IgM ELISA showed the greatest diagnostic accuracy (J=0.6) followed by rtPCR (J=0.4), cPCR (J=0.2) and IgG ELISA (J=0.1). Our results support the use of IgM ELISA and rtPCR for early diagnosis of the disease. Moreover, due to their high specificity, they could be also useful to replace or supplement microscopic agglutination test as a confirmatory test, allowing more confirmations.

Clinical characteristics and risk factors of human leptospirosis in Argentina (1999-2005).

There is scarce data on the burden of leptospirosis and its epidemiological characteristics in Argentina. This study aimed to evaluate distribution of leptospirosis cases and identify risk factors for the disease during national laboratory-based surveillance. From January 1999 to December 2005, 812 suspected cases were referred to the national reference laboratory, of which 182 and 463 had respectively, laboratory confirmed and unconfirmed diagnosis of leptospirosis. The diagnosis of leptospirosis was discarded in 167 cases. The most prevalent presumptive infecting serogroup was Icterohaemorrhagie followed by Pomona, Ballum and Canicola. The majority of cases occurred during the worm and rainy months. Confirmed cases were predominantly adults and males, who presented with fever, headache and myalgias. Severe clinical manifestations included jaundice and acute renal insufficiency. Conjunctival suffusion, a hallmark clinical sign of leptospirosis, was found in 55% of confirmed cases, and 43% of the cases with discarded diagnosis (p=0.036). After multivariate analyses, age >30 years (OR=2.16; 1.05-4.41), occupation in a rural setting (OR=3.41; 1.45-8.06), contact with contaminated surface water (OR=2.17; 1.01-4.68), and contact with floods (OR=4.49; 1.17-17.25) were significantly associated with leptospirosis. In conclusion, although activities associated with rural occupations remain important risk factors in Argentina, exposures occurring during flooding events have emerged to be the major risk factor for leptospirosis.