The comparison of microscopy, culture and molecular methods for diagnosis of tubercolosis

In our study 100 clinical specimens sent to the Firat University School of Medicine Clinical Microbiology Laboratory that was taken from different patients with a preliminary diagnosis of tuberculosis were included for mycobacterial examination. In this study we aimed to investigate the presence of TB bacilli with smear, culture and PCR methods, and also aimed to compare the specificity and sensitivity of these three methods on the samples of tuberculosis diognosed patients by considering culture gold standard. Culture positive 50 patients' samples and culture negative 50 patients' samples were included to the study for comparing the microscopic and molecular methods by considering culture the gold standard. In this study EZN was used for the microscopic examination, MGIT 960 System was used for the culture and GeneXpert MTB/RIF device was used for the molecular methods. In microscopic evaluation of 50 culture positive samples, 39 samples were AFB positive and 11 samples were AFB negative. 10 of the 11 AFB negative samples were PCR pozitive. It was detected that 49 of these 50 culture positive samples were PCR pozitive and only one of them was PCR negative. In the evaluation of 50 samples of control patients, AFB or PCR positive samples were not detected. The sensitivity of AFB and PCR were 76% and 98% respectively, and the specificity of both methods was 100%. RIF resistance was not detected in the drug susceptibility testing of 50 culture positive samples. RIF resistance was not detected similary in the evaluation of the same samples with GeneXpert MTB/RIF device. In conclusion, in this study we found that the specificity ratio of PCR and AFB was equal to each other but the sensitivity ratio of PCR was higher than AFB by accepting the culture of tuberculosis gold standard. Entering the routine use of the genexpert MTB/RIF device thought to contribute at TB diagnosis and detection of drug resistance in a positive way due to short turn around time and high sensitivity, specificity rates. Key Words: Tuberculosis, PCR, Culture, Microscopy, AFB