COMPARISON OF CONVENTIONAL METHODS, BACT/ALERT AND NESTED PCR FOR THE DIAGNOSIS OF TUBERCULOUS ARTHRITIS

Introduction: Early laboratory diagnosis of tuberculous arthritis (TBArt) is crucial to start antitubercular chemotherapy and to prevent its complications. However conventional methods are either less sensitive or time consuming. Hence the diagnostic potential of BacT/ALERT and nested polymerase chain reaction (PCR) was evaluated in this study. Method: The study group comprised of 14 cases and 12 controls. The cases were divided into confirmed sub group (three cases) ? smear or culture or histopathologically proven and probable subgroup (11 cases) - clinically suspected cases. Ziehl Nielsen (ZN), Auramine Phenol (AP) staining, LJ culture, BacT/ALERT and nested Polymerase Chain Reaction (PCR) targeting IS6110 were carried out on synovial fluid collected from all the patients. Results: Sensitivity of ZN, AP staining was found to be 14.2% each and that of LJ culture was 21.4%. BacT/ALERT showed a sensitivity and specificity of 50.0% and 100% and that of nested PCR was found to be 64.2% and 91.67% respectively. The mean detection time of growth by LJ culture was 32.10 days where as that of BacT/ALERT was 21.28 days. The contamination rate in LJ culture and BacT/ALERT were 14.2% and 7.1% respectively. Conclusion: Nested PCR is found to be more sensitive followed by BacT/ALERT compared to LJ culture and smear microscopy. As both false negative and false positive results are reported on nested PCR, so alone it should not be used as a criterion for initiating or terminating the therapy but should be supported by clinical, radiological, cytological and other microbiological finding.