Evaluation of the GeneXpert MTB/RIF assay performance in sputum samples with various characteristics from presumed pulmonary tuberculosis patients in Shiselweni region, Eswatini

Background Tuberculosis is a global health concern and has become more complex to diagnose due to mutations in the causative agent, Mycobacterium tuberculosis. In a setting with high TB prevalence, having a rapid and accurate diagnosis may reduce the rate of infections. The study aimed to evaluate the diagnostic performance of GeneXpert MTB/RIF assay in sputum samples from suspected tuberculosis patients. Methods A total of 1 328 sputum samples were collected from patients, across 12 clinics in the Shiselweni region, Eswatini. One thousand one hundred and ten (1110; 84%) samples were simultaneously processed on GeneXpert MTB/RIF assay and MGIT culture. Results Two hundred and ninety-seven (297) samples tested GeneXpert positive and 813 GeneXpert negatives, while 310 samples tested positive and 800 tested negative on the MGIT culture method. The positive predictive value on GeneXpert MTB/RIF assay was 83% while the negative predictive value was 97.80%. At p-value = .796, sputum quality did not affect the positivity of the GeneXpert MTB/RIF results. Sputum volume had a significant impact on the performance of the GeneXpert MTB/RIF with increased sensitivity in 4 ml and 6 ml samples. Conclusions Although detection of tuberculosis using the GeneXpert MTB/RIF assay in sputum samples is not limited to one specific characteristic, sputum volume assessment should be considered as an integral part of routine laboratory diagnosis of tuberculosis especially in high tuberculosis prevalent settings. However, the ability of the GeneXpert MTB/RIF to provide rapid TB diagnosis is not dependent on sputum quality.