Conventional and Molecular Methods for the Diagnosis of Smear Negative Pulmonary TB and Concordance of Empirical TB Diagnosis with Culture Assay

Abstract

Background: Ethiopia is among high TB burden countries. The proportion of smear negative patients among pulmonary TB cases was 51%. Nevertheless, microscopy is still a primary tool for TB diagnosis. In the absence of sensitive diagnostic methods, clinicians often make the diagnosis of smear-negative pulmonary TB with information obtained through the clinical history, physical examination and chest X-ray. The treatment of smear negative TB patients with those criteria largely depends on the treating clinician. There is limited data on the utilization of clinical criteria commonly used to initiate TB treatment empirically when culture is used as the reference method. Beside this, there are a number of sensitive diagnostic methods that have a substantial contribution for the diagnosis of smear negative TB patients, but only few studies were conducted in Ethiopia to address this issue. Thus, the present study is designed to assess the contribution of conventional and molecular methods for smear-negative patients and describe the concordance rate of empiric TB treatment with culture assay.

Methods: A cross-sectional study was designed on smear negative TB presumptive patients referred to St. Peter’s TB Specialized Hospital from December 2014 to June 2015. Consecutive smear negative TB presumptive patients, aged greater or equal to 15 and willing to participate were included in the study. Socio-demographic and clinical data were collected using the data collection form designed for the study purpose. The data collection form was designed to capture patient demographic data, signs and symptoms, chest X-ray findings and empirical TB treatment initiations. Spot-Moring-spot sputum was collected using sterile falcon tubes for routine diagnostic purpose. Direct ZN examination was done on Spot-Moring-spot sputum at St. Peter’s TB Specialized Hospital. The morning sputum was used for culture (LJ and MGIT), TB-LAMP, Xpert MTB/RIF assay and fluorescent microscopy examination. Data were captured and analyzed using SPSS