The Diagnostic Value of Polymerase Chain Reaction (PCR) in Bronchioalveolar Lavage

In this study we investigated the diagnostic value of polymerase chain reaction (PCR) which is fast and highly specific in terms of isolating the Mycobacterium tuberculosis (M. tuberculosis) from the bronchoalveolar lavage obtained by bronchoscopy when tuberculosis is suspected in the patients with negative sputum smears or when the sputum can not be collected. Method: Our cases consist of patients who can not expectorate or have three respective negative sputum samples taken at the morning after starvation. Fiberoptic broncoscopy was applied to all patientsunder local anestesia-at the hospital. Lavages were taken from bronchi, which were appropriate to the lesion. Lavage samples were sent to the laboratory without delay. Results were evaluated 2 days later. Totally 47 cases from 3rd Thoracic Diseases Clinic of Yedikule Thoracic Diseases and Thoracic Surgery Education and Research Hospital were included in this study. Thirty-five of the cases had a higher possibility for tuberculosis, and the remaining 12 cases had no evidence for tuberculosis (control group). In these cases M. tuberculosis complex DNA specific IS6110 field has been investigated by PCR and the results were compared with the microbiological culture, lavage AFB. Results: Twenty-one of 35 patients in the study group had positive lavage PCR results. Fourteen patients had negative lavage PCR results. Four of 21 lavage PCRpositive patients were found to be ARB positive by lavage. Nine of 21 lavage PCR positive patients were found to be ARB positive by culture. We had no false positive results. All control cases were negative in terms of AFB smear, culture, and lavage PCR. Lavage PCR sensitivity and specificity calculations were compared with ARB culture and lavage results. Considering the culture positivity as gold standard, the sensitivity and specificity of PCR were 60% and 100% respectively. Conclusion: PCR can be used as a supportive diagnostic test providing rapid and accurate results, if tuberculosis is suspected clinically and radiologicaly in patients with three consecutive AFB smear-negative sputum specimens or when the sputum can not be collected.