Usefulness of Rapid Diagnostic Tests in the Diagnosis of Active Tuberculosis

Abstract

PURPOSE: This study was to evaluate the usefulness of rapid diagnostic tests for active tuberculosis (TB). METHODS: This study included patients who were suspected active TB and performed whole blood interferon gamma assay (IGRA), CT scan, tuberculin skin test (TST), PCR, and acid-fast bacillus (AFB) stain at Chonnam national university hospital in Korea from May 2009 to May 2010. Active TB was defined by microbiologic or pathologic findings or clinical response to TB treatment. To investigate the usefulness of diagnostic tests, we evaluated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPPV) of diagnostic tests. RESULTS: Of 319 patients, 154 (48%) were active TB. Among 154 patients, 129 (84%) were pulmonary TB and 25 (16%) were extrapulmonary TB. Sensitivities and specificities were 84% and 61% in IGRA, 74% and 90% in CT scan, 62% and 78% in TST, 55% and 97% in PCR, and 34% and 96% in AFB stain. PPV and NPPV were 68% and 78% in IGRA, 88% and 82% in CT scan, 72% and 69% in TST, 94% and 70% in PCR, and 90% and 61% in AFB stain. In combination of results of all rapid diagnostic tests, sensitivity, specificity, PPV, and NPPV were 98%, 48%, 64%, and 96%, respectively. CONCLUSIONS: IGRA had a highest sensitivity and PCR had a highest specificity in rapid diagnostic tests for active TB. Combination of rapid diagnostic test results improved sensitivity and negative predictive value for the diagnosis of active TB. CLINICAL IMPLICATIONS: Combination of rapid diagnostic test results could improve the diagnosis of active TB.