Detection of mycobacterial DNA using nested polymerase chain reaction of pleural biopsy specimens: compared to pathologic findings.

Background: Although there are many methods including AFB smear and culture, and the analysis of pleural fluid in the etiological diagnosis of pleural effusion, it is sometimes difficult to confirm a diagnosis especially in cases of incomplete pleural biopsies. Moreover, the high incidence of tuberculous pleuritis in young people caused confusion in the differential diagnosis of pleural effusion in Korea. The pathognomonic finding of tuberculous pleuritis in pleural biopsy is chronic granulomatous pleuritis (CGP) with caseous necrosis. But a biopsy does not always provide a definitive diagnosis, which shows in only 60-70% of all biopsies, because of either limitations in blind biopsies or inadequate specimens. An adequate biopsy also gives only limited information, such as chronic or nonspecific pleuritis.

Methods: We compared the clinical diagnosis, pathologic findings and detection of mycobacterial DNA using nested PCR of pleural biopsy tissues. We carried out the nested PCR for IS6110 insertion sequence of Mycobacterium tuberculosis using outer primer IS-1/IS-2 (5'-AGGCGTTGGTTCGCGAGGG-3'/5'-TGATGACGCCCTCGTTGCC-3') and inner primer IS-3/IS-4 (5'-CCAACCCGCTCGGTCTCAA-3'/5'-ACCGATGGACTGGTCACCC-3') in 52 pleural biopsy tissues which were pathologically diagnosed as tuberculous pleuritis, malignant pleuritis or non-specific pleuritis.

Results: Five (71.4%) of 7 cases clinically and pathologically confirmed tuberculous pleuritis diagnosed as chronic granulomatous pleuritis (CGP) with caseous necrosis revealed positive in nested PCR for M. tuberculosis. Seven (36.8%) of 19 cases diagnosed as CGP without caseous necrosis were positive. However, only 3 (25%) of 12 cases diagnosed as non-specific chronic pleuritis were positive by PCR for M. tuberculosis. Neither congestive heart failure nor malignancies with pleurisy showed a positive reaction.

Conclusion: In this study, pathologic findings were significantly associated with the detection rate of mycobacterial DNA. And, even in patients with nonspecific or chronic inflammatory pleuritis, mycobacterial DNA could be detected by using nested PCR in pleural biopsy tissue with good specificity. Detection of mycobacterial DNA in pleural tissue might provide additional information for etiological diagnosis in patients with pleural effusion.