The value of the tuberculin skin test in patients with tuberculous meningitis.

To determine the clinical utility of the tuberculin purified protein derivative (PPD) skin test in patients suspected of having tuberculous meningitis (TBM), the test was applied on admission to 180 patients suspected of having tuberculous meningitis and to 50 patients with proven bacterial meningitis admitted to the Abbassia Fever Hospital, Cairo, Egypt, during the period 1987 to 1989. Admission tuberculin positivity in evaluated groups revealed the following: overall suspect TBM cases--17% (31/180), culture-confirmed TBM cases--19% (16/83), and culture-confirmed acute bacterial meningitis cases--14% (7/50). Repeat PPD skin test at 60 days in surviving presumptive/confirmed TBM cases revealed a significant increase in tuberculin positivity to 62% (58/93) from admission (p < 0.001). Evaluation of PPD positivity by clinical stage of TBM revealed 36% positivity in alert patients as compared to 12% positivity in comatose patients (p = 0.01). Admission tuberculin skin testing as a diagnostic aid for clinical management of tuberculous meningitis is of limited utility in our study population because of the high prevalence of tuberculin positivity in the Egyptian population (potential false positive correlation with the acute presentation) and the advanced stage of TBM at presentation to Egyptian public hospitals (potential false negative correlation).