Diagnosis of extrapulmonary tuberculosis by smear, culture, and PCR using universal sample processing technology

Abstract

Definitive and rapid diagnosis of extrapulmonary tuberculosis is challenging since conventional techniques have limitations. We have developed a universal sample processing (USP) technology for detecting mycobacteria in clinical specimens. In this study, this technology was evaluated blindly on 99 extrapulmonary specimens collected from 87 patients. USP-processed specimens were submitted to smear microscopy for detection of acid-fast bacilli (AFB), culture, and two PCR tests targeting devR (Rv3133c) and IS6110 gene sequences. On the basis of clinical characteristics, histology and cytology, conventional microbiology results, and response to antitubercular therapy, 68 patients were diagnosed with tuberculosis. Although USP smear and culture were significantly superior to conventional microbiology, which was not optimized (P < 0.0001), these approaches fell short of PCR tests (P < 0.0001). The low yields by smear and culture are attributed to the paucibacillary load in the specimens. The highest sensitivity in PCR was achieved when devR and IS6110 test results were combined; the sensitivity and specificity values were 83 and 93.8%, 87.5 and 100%, and 66.7 and 75%, respectively, in pleural fluid, needle-biopsied pleural tissue, and lymph node specimens. In conclusion, the application of USP technology, together with clinicopathological characteristics, promises to improve the accuracy and confidence of extrapulmonary tuberculosis diagnosis.