Typhoid fever in Kuala Lumpur and a comparative evaluation of two commercial diagnostic kits for the detection of antibodies to Salmonella typhi

The aim of this study was to compare two commercial kits, theTyphidot and the PanBio ELISA with the present Widal test. Demographic data for all serodiagnosed cases for the years 1991-1998 were collected. From this data, 144 were selected as samples for comparative evaluation of the commercial kits. Fifty sera were culture positive for Salmonella typhi, 50 were culture negative but clinically diagnosed as typhoid fever and Widal positive and 44 were serodiagnosed as enteric of which 21 were culture positive for other Salmonella species, 20 were serodiagnosed for other febrile illnesses and three sera culture positive for other species of enterobacteriaceae. The specificity, sensitivity and efficiency of the tests were calculated with the positive culture for S. typhi as the gold standard. Sensitivity, specificity and efficiency of test for Typhidot and Typhidot M kits were 98%, 76.6% and 84.0% and PanBio ELISA were 78%, 80% and 79.9%. The two commercial kits evaluated were found to be less time consuming and easier to perform than Widal. The Typhidot M seems to be a practical alternative in the field and in small hospitals with lesser facilities.

Leptospirosis in Kuala Lumpur and the comparative evaluation of two rapid commercial diagnostic kits against the MAT test for the detection of antibodies to leptospira interrogans

The aim of the study was to look into the epidemiology of serodiagnosed cases of leptospirosis at the University Hospital and compare two commercial ELISA Assays to the Microscopic Agglutination Test (MAT). Demographic data for all serodiagnosed cases for the years 1991-1997 were collected. From this data, 104 sera (n = 104) were selected as samples for comparative evaluation of the commercial ELISAs (INDX Dip-S-Ticks and PanBio ELISA) to the MAT test. Thirty two (n = 32) negative control sera were selected from serodiagnosed cases of other differential diagnosis of leptospira infection. The MAT test is a standard test that detects agglutination antibodies to leptospira biflexa, while the INDX Dip-S-Ticks is an ELISA dot test assaying for total anti-leptospira antibodies. The PanBio ELISA is a colorometric assay in test well strips to detect anti-leptospira IgM. The sensitivity, specificity, and efficiency of tests were calculated at a MAT cut-off value of 1:320. Demographic data showed that leptospirosis peaks during March-May and Aug-Nov coinciding with the inter-monsoon period with more men being infected than women and more adults than children. The sensitivity, specificity, and efficiency of test for the INDX Dip-S-Ticks were 83.3%, 93.8% and 87.5% while the values for the PanBio ELISA were 54.2%, 96.9% and 71.3%. The suboptimal PanBio result could be related to the blocking effect of high IgG titres or could be related to the diagnostic MAT cut-off values used in this study. The data hence reflects a pattern of transmission that is related to "wet" occupational risk factors. The commercial assays evaluated, are easier to perform but interpretation of results should be based on level of endemicity. The INDX Dip-S-Ticks allows this flexibility and is a practical alternative to the MAT test.