Pus cell as an indicator for Mycobacterium tuberculosis diagnostic yield by GeneXpert MTB/RIF in South-South Nigeria: A prospective study

Background: The common problem in tuberculosis (TB) management is mis-diagnosis or under diagnosis of cases leading to high morbidity and mortality. In order to reverse this, new diagnostic tools for detection of Mycobacterium tuberculosis (MTB) have been developed. However, in the evaluation process of these tools many studies have not considered attributes of sputum quality in their testing algorithm. The performance of laboratory tests to diagnose pulmonary tuberculosis is dependent on the quality of the sputum sample tested and quality is measured by the number of pus and epithelial cells present in sputum. Aims and Objectives: this study aimed at investigating the association between pus cell and MTB positivity. Methods: Sputum samples from 140 suspected TB participants were screened for sputum quality and MTB using macroscopy, Ziehl-Neelson staining and GeneXpert techniques. Results: Of the 140 sputum samples subjected to AFB microscopy and GeneXpert MTB/RIF assay, GeneXpert assay had 32 (22.9%) MTB positives while AFB smear had 27 (19.3%) MTB positives and there was no significant relationship between sputum type and MTB yield by AFB compared to Xpert that showed significant relationship between sputum type and MTB yield with P<0.005. Out of the 37 sputum samples with pus cells ≥25, 29 (90.6%) were MTB positive by Xpert and 25 (92.6%) were MTB positive by AFB smear. Conclusion: In conclusion, our study shows a high significant association between pus cells presence and the methods and therefore suggests that presence of pus cells in sputum is predictive for possible positivity to MTB by Xpert MTB/RIF.