The diagnosis of current leptospirosis is confirmed by 1) positive cultures 2) sero-conversion / four-fold rise in MAT titres . This would require two samples to be taken & this is usually difficult to obtain,since patients when they recover do not give the second sample . Therefore , a single high titre in MAT is considered adequate for diagnosis .But high titres of past infection can persist for a long time ( 5-10 yrs ) & interfere with current diagnosis . Hence , combining positive Elisa IgM + positve MAT would confirm diagnosis of current leptospirosis . A negative Elisa IgM + positive MAT would suggest past infection .
Article Leptospirosis in Madras--a clinical and serological study
The Elisa IgM is a simple test for diagnosis of current leptospirosis with good sensitivity & specificity & can be diagnosed in single samples by fifth day . It is available in most laboratory diagnostic facilities & measures IgM antibodies which is diagnostic of current infection . The MAT is considered the gold standard test , but it has low sensitivity for diagnosis in the first week for single samples & is a complicated test , which can be done only in specialized laboratories . Seroconversion / four fold rise in MAT titres confirm the diagnosis of current leptospirosis & therefore needs two samples .
Since the clinician needs an early diagnosis to confirm the diagnosis , a single high titre MAT of 1/400 or more , has been suggested as the diagnostic titre . In addition , since most of the samples are obtained between the 5th to 10th day , a MAT titre may be in the range of 1/100 - 1/200 . But these titres may represent a rising titre of current infection or declining titre of past infection as MAT titre can persist for 5 - 10 years . Therefore , we have suggested that combining positive Elisa IgM with single high titre MAT should confirm the diagnosis of current leptospirosis .
If MAT is not available , Elisa IgM is adequate for the diagnosis of leptospirosis , along with clinical & epidemiological parameters . This would be relevant for developing countries , with limited laboratory facilities to diagnose leptospirosis utilizing MAT . This has been utilized in the Modified Faine's criteria for diagnosis of leptospirosis .
The article cited below has utilized Elisa IgM & MAT to establish a valid laboratory case definition for diagnosis of human leptospirosis .
http://dx.doi.org/10.4172/2155-9597.1000132
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