Evaluation of TBc identification immunochromatographic assay for rapid identification of Mycobacterium tuberculosis complex in samples from broth cultures

Abstract

Tuberculosis (TB) is a disease of major public health concern worldwide, especially in developing countries. In addition, the human immunodeficiency virus (HIV) epidemic has increased the incidence of infection with nontuberculous mycobacteria (NTM). Rapid, accurate, and simple methods for differentiation of Mycobacterium tuberculosis complex (MTBC) isolates from NTM is greatly needed for successful control of the TB epidemic. This study was done to evaluate the clinical performance of the BD MGIT TBc identification test (TBc ID) for rapid identification of MTBC in samples from broth cultures. A total of 229 Ziehl-Neelsen (ZN) stain-positive MGIT cultures were tested using the TBc ID test, and the results were compared with those of the AccuProbe MTBC identification test (GenProbe, San Diego, CA). The agreement between the TBc ID test and the AccuProbe assay was 96% (kappa 0.92; confidence interval [CI] 0.869 to 0.971). The sensitivity, specificity, and negative and positive predictive values of the TBc ID test compared to the AccuProbe assay were 100%, 92.4%, 100%, and 92.2%, respectively. After additional molecular testing, the agreement between the two methods increased to 97.8% (kappa 0.96; CI 0.917 to 0.994), and the specificity and positive predictive value increased to 95.6% and 95.7%, respectively. The TBc ID test is a simple, sensitive, and specific test for identification of MTBC in samples from acid-fast bacillus (AFB) smear-positive cultures. The TBc ID test could be a good alternative to the AccuProbe test in TB diagnostic laboratories.