Comparison of Polymerase Chain Reaction, Ziehl-Neelsen Staining and Histopathologic Findings in Formalin-fixed, Paraffin-Embedded Tissue Specimens for Diagnosis of Tuberculosis
Background and Objective: Tuberculosis is still a major health problem, involving about 1/3 of the world´s population. Diagnosis is difficult when we only use Ziehl-Neelson staining. Many cases may be missed. A more rapid and sensitive diagnostic method is necessary. PCR may be helpful. The aim of this study is to compare PCR, Zieh-Neelsen staining and histopathologic findings in diagnosis of tuberculosis on formalin-fixed paraffin-embedded tissues. Methods: Paraffin blocks of the submitted specimens of the patients clinically suspicious for tuberculosis or containing granuloma were selected. Ziehl-Neelsen Staining & TB-PCR (IS6110 element) were carried out. The results of the tests were compared by using the McNemar test. Statistical significance was accepted when the P value was less than 0.05. Results: Forty five specimens were included in the study, 35 had granulomas (19 with caseous necrosis). Acid-fast bacilli were identified in 17 specimens (37.8%). TB-PCR was positive in 16specimens (84%) with caseating granulomas, 11 specimens (68.8%) with non-caseating granulomas & 6 specimens (60%) without granulomas. (P value = 0.59). Conclusions: TB-PCR on paraffin–embedded tissue is a potentially useful approach for early, rapid and sensitive diagnosis of tuberculosis. It is especially useful when granuloma is seen in tissue section, while acid-fast stain is negative. If there was no facilities for PCR, histopathological diagnosis with clinical correlation is more reliable in comparison to AFB results.