CLINICAL-EVALUATION OF THE GEN-PROBE AMPLIFIED DIRECT TEST FOR DETECTION OF MYCOBACTERIUM-TUBERCULOSIS COMPLEX ORGANISMS IN CEREBROSPINAL-FLUID

Eighty-four cerebrospinal fluid (CSF) samples from different children who presented with signs and symptoms of meningitis were evaluated for the presence of Mycobacterium tuberculosis complex organisms by the G en-Probe Amplified Mycobacterium tuberculosis Direct Test (MTD; Gen-Pr obe, San Diego, Calif). All CSF samples had negative acid-fast smears by the Ziehl-Neelsen staining method. M. tuberculosis was recovered fr om five samples. M. tuberculosis did not grow from 19 additional sampl es, but the samples were from patients who fulfilled specific clinical and laboratory criteria for probable tuberculous meningitis (TBM). Th e remaining samples (n = 60) were from patients with other infections or noninfectious causes of meningitis. The results of the MTD were int erpreted as positive or negative on the basis of recommended cutoff va lues for respiratory specimens. These results were interpreted as true or false positives Or true or false negatives on the basis of the res ults of M. tuberculosis culture or whether the patient fulfilled crite ria for probable TBM. The Gen-Probe MTD was 33% sensitive and 100% spe cific for detecting M. tuberculosis complex organisms in these 84 CSF samples. If the cutoff values for positive results were decreased for the MTD (greater than or equal to 11,000 versus greater than or equal to 30,000 relative light units), the sensitivity increased to 83% and the specificity remained 100%. These results for the MTD are encouragi ng considering that TBM is a highly fatal disease and difficult to dia gnose by conventional laboratory techniques.