Evaluation of a membrane array for detection of Mycobacterium tuberculosis complex and nontuberculous mycobacteria in positive liquid cultures

Molecular identification of mycobacteria in positive Mycobacteria Growth Indicator Tube (MGIT) cultures can accelerate mycobacterial diagnosis. A membrane hybridization array (Blue Point) was evaluated for this purpose in 284 positive MGIT cultures. Discrepant results were resolved by testing with the GenoType Mycobacterium kit, TBc ID test, sequencing of the 16S rRNA gene and internal transcribed spacer. Total recovery from culture and the array (if confirmed) was considered 100%. The sensitivity, specificity, positive, and negative predictive values of the array for detection of Mycobacterium tuberculosis complex were 99.4%, 100%, 100%, and 99.2%, respectively, while the corresponding values of culture were 95.1%, 100%, 100%, and 93.8%, respectively, with significant differences in sensitivity and negative predictive value being found between the 2 methods. The recoveries of nontuberculous mycobacteria and mixed cultures of the array were also significantly higher than those of culture. The array can be adopted in routine mycobacteriology laboratory.