Sputum Quality Challenges the Point of Care Diagnostic System of Pulmonary Tuberculosis in the Republic of Congo

The quality of sputum specimen remains crucial in the accurate diagnosis of TB. Good quality sputum makes for a high diagnostic yield while poor quality sputum yields false negative results and delays diagnosis. We aimed to determine the effect of sputum quality on smear microscopy results in a referral hospital in the Republic of Congo. The Sputum specimens were collected from suspected pulmonary TB patients and macroscopically observed using set quality parameters and then processed using standard Ziehl-Neelsen (ZN) staining for Acid fast bacilli (AFB). A total of 117 TB suspected patients submitted 229 sputum samples that was processed. Out of the 229 samples, 24.02% were of good quality (mucopurulent), 1.31% of average quality (blood tinged) and 72.49% of poor quality (saliva). There were 61 samples (26.64%) that tested positive for AFB while 168 (73.36%) were negative. The positive samples were mainly mucopurulent 88.52% (54/61), while the negative samples were mainly salivary 97,62% (164/168). Thus, 37 (31,62%) patients were diagnosed AFB smear positive (AFB+) and 80 (68.38%) AFB smear negative (AFB-). Smear negative TB was associated with poor quality sputum (saliva). The results of this study show that the quality of the sputum influences significantly the performance of microscopy for the diagnosis of pulmonary tuberculosis and reveals the fact that inadequate sputum quality compromises the national efforts to control TB. In our study we had a good performance of the macroscopic assessment that identified smear-positive respiratory specimens associated with mucopurulent sputum and smear-negative respiratory specimens associated with saliva.