Epidemiology of Tuberculosis with comparison of the efficacy of culture, real-time PCR and direct microscopy in the diagnosis of tuberculosis

Abstract

Aim: Despite the developments every passing year, tuberculosis is still a major public health problem in Turkey and in the world. Early and correct diagnosis is important for the control of the disease. The aim of this study is to investigate the diagnostic efficiency of the culture (Lowenstein Jensen), real-time PCR (Abbott m2000rt, Bosphore MTBC Detection Kit) and direct microscopic examination of acid-resistant bacillus stained with Ehrlich-Ziehl-Neelsen (EZN), and the study was performed by evaluating the samples coming to our laboratory retrospectively over a 4-year period.

Material and Methods: The samples sent to our mycobacteriology laboratory between January 2016 and December 2019 were evaluated retrospectively. The effects of direct microscopy and real-time PCR method were compared based on culture as a reference method.

Results: Sensitivity, specificity, positive predictive value and negative predictive value of direct microscopy were calculated as 45%, 99.9%, 96.4%, 96.9%, respectively, in pulmonary samples and as 21.7%, 100%, 98.8%, 98.8%, respectively, in extrapulmonary samples. Sensitivity, specificity, positive predictive value and negative predictive value of real-time PCR were calculated as 80%, 98.3%, 98.8%, 97.3%, respectively, in pulmonary samples and as 62.5%, 99.2%, 50%, 99.5%, respectively, in extrapulmonary samples.

Discussion: Although direct microscopic examination method is a cheap, simple, fast and highly specific test, its sensitivity is low. Therefore, patients with suspected tuberculosis should be evaluated together with culture, besides direct microscopy. It was observed that the sensitivity of direct microscopy was lower in extrapulmonary samples compared to pulmonary samples. The real-time PCR method has high sensitivity and specificity, and also gives fast results.