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™ 960™ 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.