Clinical usefulness of the nested polymerase chain reaction in the diagnosis of extrapulmonary tuberculosis.

OBJECTIVE To evaluate the effectiveness of nested polymerase chain reaction (PCR) for diagnosis of extrapulmonary tuberculosis (ETB), as well as the impact of PCR results on clinical management. MATERIALS AND METHODS We conducted a study of nested PCR tests in 45 patients and a review of patient hospital files, calculating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). RESULTS PCR was positive in 51% of cases; PCR sensitivity for diagnosing TB was 86%, specificity was 79%, PPV was 76%, and NPV was 88%. When solely analyzing urine samples, sensitivity and NPV increased to 100%. PCR exerted an influence on management in 27% of patients. CONCLUSIONS PCR for rapid diagnosis of extrapulmonary TB has an adequate effect, which improves when performed on urine. The results of PCR exerted an acceptable impact on the clinical management of these patients.