Performance Of A Pyrosequencing Platform In Diagnosing Drug-Resistant Extra-Pulmonary Tuberculosis In India

SETTING: Pyrosequencing diagnostic assays have shown great utility in identifying and characterizing pulmonary drug-resistant tuberculosis (TB) infections. However, the method has yet to be evaluated for the diagnosis of drug-resistant extra-pulmonary TB (EPTB).OBJECTIVE: To evaluate the performance of a pyrosequencing platform in establishing molecular drug resistance profiles for 79 clinical EPTB specimens at a referral center for drug-resistant TB in India.DESIGN: Genotypic drug resistance profiles were established for all 79 non-pulmonary, culture-positive TB clinical specimens. Acid-fast bacilli smear microscopy, MGIT (TM) 960 (TM) culture and drug susceptibility testing were performed on all specimens for reference.RESULTS: In comparison to MGIT 960, the sensitivity and specificity of pyrosequencing in detecting drug resistance among specimens was found to be respectively 100% and 100%, 67% and 98%, and 100% and 100% for isoniazid, rifampicin, and the fluoroquinolones. No EPTB specimens were phenotypically resistant to any of the injectables, but the specificity of the assay was determined to be 100%, 98%, and 98% for amikacin, kanamycin, and capreomycin.CONCLUSIONS: Pyrosequencing is a rapid, appropriate technology for the diagnosis of isoniazid-, fluoroquinolone-, and potentially injectable drug-resistant EPTB. clinical specimens, and should be considered as an alternative to conventional growth-based diagnostic methods for EPTB when resistance to these drugs is suspected.