DIAGNOSTIC PERFORMANCE OF AMPLIFIED MYCOBACTERIUM-TUBERCULOSIS DIRECTTEST WITH CEREBROSPINAL-FLUID, OTHER NONRESPIRATORY, AND RESPIRATORY SPECIMENS

The Gen-Probe Amplified Mycobacterium tuberculosis Direct Test (MTD) w as adapted to be used for cerebrospinal fluid (CSF) and a large variet y of other nonrespiratory specimens, Standardized with artificially sp iked dilution series of CSF, the modified MTD procedure consists of (i ) increasing the amount of sample 10-fold, (ii) pretreating the specim en with a detergent, and (iii) increasing the amplification time from 2 to 3 h, Performance of MTD in a clinical mycobacteriology laboratory was tested over an extended period of time, involving a total of 322 nonrespiratory as well as 1,117 respiratory specimens from 998 patient s, Results from MTD were compared with those from microscopy, culture, analysis of tuberculostearic acid by gas-liquid chromatography-mass s pectrometry (CSF only), and the final clinical diagnosis, When MTD res ults were compared with resolved data, the sensitivity, specificity, a nd positive and negative predictive values for MTD were 93.1, 97.7, 90 .0, and 98.5%, respectively, for nonrespiratory specimens and 86.6, 96 .4, 76.8, and 98.1%, respectively, for respiratory specimens. Our data demonstrate that (i) MTD is a robust, highly sensitive and specific t echnique for the rapid detection of M. tuberculosis complex in all typ es of clinical specimens, (ii) there was no statistically significant difference (P > 0.005) in sensitivity and specificity for nonrespirato ry compared with respiratory specimens, and (iii) repeating all MTDs w hich yield a result between 30,000 and 200,000 relative light units wo uld help prevent a large number of false positives and, thus, enhance test specificity.