Evaluation of a liquid culture system in the detection of mycobacteria at an antituberculosis institution in China; A retrospective study

OBJECTIVE: A retrospective study comparing the diagnostic performance of the BACTEC™ MGIT™ 960 system (M960 system; BD Worldwide, Franklin Lakes, NJ, USA) with Löwenstein–Jensen (L–J) culture to detect mycobacteria in sputum specimens from patients with suspected pulmonary tuberculosis (TB). METHODS: Sputum samples were analysed for the presence of acid-fast bacilli (AFB). Samples were inoculated into the M960 system and L–J culture. Positive cultures were examined for the presence of AFB. RESULTS: The M960 method detected significantly more positive samples than L–J culture (818/1676 [48.8%] vs 692/1676 [41.3%]). Using L–J culture as reference, the sensitivity, specificity, positive predictive and negative predictive values of the M960 system were 91.0%, 76.1%, 77.0% and 92.2%, respectively. The time-to-detection of mycobacteria was 11.78 ± 5.16 days for M960 and 24.17 ± 8.73 days for L–J. CONCLUSIONS: The M960 system had better diagnostic capability than L–J culture. Clinical value may be maximized by combining results from both methods.