Clinical Usefulness of PCR for Differential Diagnosis of Tuberculosis and Nontuberculous Mycobacterial Infection in Paraffin-Embedded Lung Tissues

The need for isolation of nontuberculous mycobacteria (NTM) from clinical specimens has increased in recent years. Our aim was to determine the clinical usefulness of PCR for differential diagnosis of tuberculosis and nontuberculous mycobacterial infection in lung tissue that show chronic granulomatous inflammation. A total of 199 formalin-fixed, paraffin-embedded specimens, including 137 Mycobacterium tuberculosis (MTB), 17 NTM cases, and 45 other than mycobacterial cases were collected. We performed acid-fast staining, MTB and NTM nested PCRs, and MTB and NTM real-time PCRs. No histologic difference between MTB and NTM infections was observed. Sensitivity and specificity for detecting MTB were 70.1% and 95.1% by nested PCR, respectively, and 70.8% and 100.0% by real-time PCR, respectively. Sensitivity and specificity for detecting NTM were 52.9% and 96.15% by nested PCR, respectively, and 35.3% and 100.0% by real-time PCR, respectively. Mycobacteria were identified by acid-fast staining in 50 of 154 cases (32.5%). All 50 acid-fast staining-positive cases showed positive nested and real-time PCR results (n = 47 MTB PCR positive; n = 3 NTM PCR positive), and results agreed with final diagnosis. PCR will be useful for the rapid diagnosis of mycobacterial infection and differentiation of MTB from NTM in formalin-fixed, paraffin-embedded specimens, especially in acid-fast staining-positive specimens.