Clinical evaluation of a commercial ligase-based gene amplification method for detection of Mycobacterium tuberculosis.

The purpose of this study was to evaluate the clinical usefulness of a commercial ligase-based gene amplification method (LCx Mycobacterium tuberculosis test; Abbott Laboratories, USA) for detection of Mycobacterium tuberculosis. The tuberculosis infection rate among clinical samples was 10.6%. The sensitivity, specificity, and positive and negative predictive values were 23.5%, 100%, 100%, and 91.7%, respectively, with the fluorochrome auramine stain; 32.4%, 100%, 100%, and 92.6%, respectively, with culture; and 76.5%, 95.8%, 68.4% and 97.2%, respectively, with the gene amplification method. When only samples from patients without current or previous treatment were studied, the sensitivity was 36.4% with the auramine stain, 63.6% with culture, and 100% with the gene amplification assay. The mean treatment time for culture-negative and assay-negative samples was greater than that of culture-negative and assay-positive samples. The LCx Mycobacterium tuberculosis test is a sensitive method for detection and identification of Mycobacterium tuberculosis. It produces few false-positive results. However, as it can remain positive after the culture becomes negative, it is not recommended for evaluation of treatment efficiency.