Comparison between Xpert MTB\RIF Threshold Cycle Value and Smear Microscopy of Bronchial Lavage for Diagnosis of Pulmonary Tuberculosis in Bronchoscoped Patients

Abstract

arly diagnosis and initiation of treatment is very important for tuberculosis (TB) control. Smear status has historically been the initial microbiology test to address patients' infectiousness and was also used to aid health care decisions regarding patient isolation as well as contact investigations (Hobby et al., 1973). A positive smear result reinforces the suspicion of TB and is associated with a high transmission risk (Nelson et al., 1998; Opota et al., 2016). However, it has a limited sensitivity and is unable to distinguish between non-tuberculosis mycobacteria and MTB. To address these limitations, the World Health Organization has recommended the GeneXpert (GX) as the initial test for pulmonary TB diagnosis (WHO, 2013a). The XpertMTB/RIF (Xpert) assay offers rapid TB diagnosis and quantitative estimation of bacterial burden through Cycle threshold (Ct) values. The priority of Xpert MTB/RIF as a diagnostic method of PTB was related to its suitability and feasibility as quick, reliable, controllable, effortless, timed, and economic test. The GeneXpert (GX) estimates mycobacterial load by measuring the threshold-cycle (Ct) which can predict the infectiousness of the patients and hence the possibility of making the decision to isolate and treat the patient.