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

Abstract

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.