Validation of the FluoroType^® MTBDR assay using respiratory and lymph node samples

Tuberculosis (TB), especially drug-resistant TB, is a global public health problem. This study aimed to validate a new molecular diagnostic test, the FluoroType^® MTBDR.

Samples underwent routine diagnostic procedures (fluorescence microscopy, culture, species differentiation and phenotypic drug susceptibility testing). Left over samples stored at -20° underwent DNA extraction using the Fluorolyse^® kit, followed by FluoroType^® MTBDR and Genotype MTBDRplus testing.

A total of 350 respiratory and 59 lymph node samples were included in the study; 71 respiratory and 16 lymph node samples were culture positive for M. tuberculosis complex (MTBC). The sensitivity of the FluoroType^® MTBDR to detect MTBC DNA was 91.4% (95%CI 82.3-96.8%), 68.4% (95%CI 43.4-87.4%) and 62.5%, (95%CI 35.4-84.8%) for respiratory, smear negative respiratory and lymph node samples respectively. The correlating sensitivities of the GenoType MTBDRplus were 85.9% (95%CI 75.6-93.0%), 52.6% (95%CI 28.9-75.6%) and 56.3% (29.9-80.2). Sensitivity of the FluoroType^® MTBDR to detect RMP and INH resistance for respiratory samples was 96.5% (95%CI 82.2-99.9) and 70% (95%CI 45.7-88.1), respectively. The GenoType MTBDRplus revealed sensitivities of 97.1% (95% 85.1-99.9) 70.6% (95%CI 52.5-84.9) for detection of RMP and INH resistance. Indeterminate results were 13/64 (20.3%), 23/64 (35.9%) and 16/64 (25.0%) for rpoB, katG and inhA using the FluoroType^® MTBDR.

The FluoroType^® MTBDR has a high sensitivity to detect MTBC DNA. However, the high proportion of indeterminate results across all three genes needs to be addressed.