Front-loaded sputum microscopy in the diagnosis of pulmonary tuberculosis

Objective/background: The objectives of this study are to describe the acid-fast bacilli (AFB) yield of a front-loaded scheme in which an additional on-the-spot specimen (Xspot [Xs]) was collected 1 h after the first spot specimen and to compare the default rate between the front-loaded and standard schemes. The performance of the front-loaded sputum microscopy was also compared with the standard World Health Organization (WHO) method for the diagnosis of pulmonary tuberculosis (PTB) in Anambra State, Nigeria. Methods: A total of 1487 individuals with presumptive pulmonary TB participated. Participants' age ranged from 15 years and above. Three sputum specimens were submitted as spot-early morning-spot. An additional specimen (Xs) was submitted 1 h after the first spot. The sputum smears were stained using the Ziehl-Neelsen technique. Results: A total of 183 (12.3%) patients were AFB positive. The front-loaded scheme identified 182 (99%) TB patients, whereas the standard scheme identified 183 (100%) TB patients. The difference was not statistically significant (p > .05). The first two specimens of each scheme (S-Xs vs. S-M) identified 176 (96.2%) and 181 (98.9%) of PTB patients, respectively. Neither difference was statistically significant (p > .05). Default during the diagnostic process was 11% in the standard but only 0.7% in the front-load scheme. The difference was significant (p < .05). Conclusion: Front-loaded smear microscopy has similar performance compared with the standard scheme. More presumptive PTB cases defaulted in the standard than in the front-loaded scheme. Front-loaded smear microscopy could therefore be used in the diagnosis in PTB in Anambra State.