Reverse passive haemagglutination (RPHA) test for detection of mycobacterial antigen in the cerebrospinal fluid for diagnosis of tubercular meningitis.

BACKGROUND: Various serological techniques have been developed to detect antibodies and antigens in the cerebrospinal fluid (CSF) for diagnosis of tubercular meningitis. Most of the serological assays are ELISA based. Attempts have been made to use much simpler antigen detection techniques like the reverse passive haemagglutination (RPHA)which is simple and cost-effective. AIMS: To evaluate the reverse passive haemagglutination (RPHA) test for detection of mycobacterial antigens in the CSF for diagnosis of tubercular meningitis. METHODS: In the present study, we have made the use of polyclonal antiserum against heat killed whole Mycobacterium tuberculosis bacilli to sensitize the RBCs in RPHA to detect antigens in clinically suspected cases. A total of 46 cases (clinically suspected TBM 24, culture proven TBM 2, non- TBM cases 20) were included in the present study for detecting M. tuberculosis antigen in the CSF specimens. RESULTS: Of the 26 test CSF specimens, 13 CSF specimens were positive by RPHA while 4 of the 20 control CSF specimens were also reactive. Two culture positive specimens included in the study were positive by RPHA. Of the 4 control CSF specimens positive by RPHA, 3 were culture proven cases of pneumococcal meningitis and 1 was a case of cryptococcal meningitis. The RPHA is found to be 50% sensitive and 80% specific; and showed a 76.4 % positive predictive value and a 55.2 % negative predictive value. CONCLUSION: The RPHA is a simple test that could be used as an adjunct in diagnosing TBM. It does not require any special equipment or technically trained or skilled manpower. It is economical and can be afforded for use in community where TBM is more prevalent. Even though the present study showed a poor sensitivity and specificity, further identification, characterization and evaluation of better immuno-dominant and specific antigens or epitopes, and the usage of antibodies developed against such mycobacterial antigens might improve the sensitivity and specificity of this test.

Comparison of Siriraj and Guy's Hospital score to differentiate supratentorial ischaemic and haemorrhagic strokes in the Indian population.

In India, 70% of the population does not have access to computerised brain scanning. Siriraj score is a safe and reliable clinical method to asses acute stroke syndrome. 160 patients with acute stroke were analysed by Siriraj and Guy's hospital stroke score simultaneously. CT Scan was performed in all and subarachnoid haemorrhage was excluded. Ninety two patients (57.5%) had infarction and 68 (42.5%) had haemorrhage. Siriraj score formula revealed haemorrhage in 53 (80%) and infarction in 78 (83%), while in the rest the results were equivocal or incorrect. Guy's hospital score revealed haemorrhage in 45 (66%) and infarction in 59 (69%). Clinical features are also helpful in differentiating infarction from haemorrhage, but the accuracy is not as high as with Siriraj score and secondly Siriraj score is a very simple formula in comparison to Guy's score.