Diagnostic Performance of Xpert MTB/RIF Assay in Adults with Presumed Pulmonary Tuberculosis at Uyo, Nigeria.

Background: Tuberculosis (TB) is a disease of immense public health importance in sub-Saharan Africa. Xpert MTB/RIF assay, a relatively recent, rapid molecular testing modality offers potential solutions to most of the challenges associated with TB diagnosis.

Objective: This study determined the diagnostic performance of Xpert MTB/RIF assay in adults with presumed pulmonary tuberculosis (PTB).

Methods: This was a descriptive cross-sectional study involving consenting adults with presumed PTB at the University of Uyo Teaching Hospital, Uyo, southern Nigeria. A structured questionnaire was used to collect participants' data. All participants submitted 2 sputum samples (spot and early morning). Sputum smear microscopy, Xpert MTB/RIF assay and mycobacterial culture were done. They also had chest radiography.

Results: They were 230 participants in the study. Seventy-nine (34.3%) patients were living with HIV. Xpert MTB/RIF assay detected MTB in 65 (28.3%) patients with 2 (3.1%) of them having rifampicin resistance. M. tuberculosis was isolated from sputum culture in 69 participants while the result was negative in 151 participants. The culture results of these 220 patients were used as the reference standard for the determination of the sensitivity and specificity of Xpert MTB/RIF assay. The overall sensitivity and specificity of the assay were 88.4% and 98.7% respectively. Younger age, longer duration of cough, weight loss, low body mass index (BMI) and positive smear status were independent factors associated with MTB detection using the assay.

Conclusion: Xpert MTB/RIF assay is a highly sensitive and specific modality for pulmonary TB diagnosis when compared with mycobacterial culture, which is the gold standard.