Sensitivity and specificity of an index for the diagnosis of TB meningitis in patients in an urban teaching hospital in Malawi.

Tuberculous (TB) meningitis is difficult to diagnose and has a high mortality rate, particularly when presentation is delayed. A diagnostic index developed in Vietnam, an area of low-HIV seroprevalence, has been proposed as a means to differentiate TB meningitis from acute bacterial meningitis using clinical and laboratory features. We applied this index over a 4-month period to adults presenting with meningitis to an urban teaching hospital in Malawi, where HIV seroprevalence is 70% among medical inpatients. Eighty-five consecutive eligible patients were studied. Nine had TB meningitis, 64 bacterial meningitis and 12 cryptococcal meningitis. The sensitivity of the diagnostic index for predicting TB meningitis was 78%, with a specificity of 43%, too low to be used in the diagnosis of TB meningitis in this setting. This finding is likely to be generalizable to other southern African countries with similarly high-HIV seroprevalences.