Front-loaded sputum microscopy in the diagnosis of pulmonary tuberculosis

AbstractObjective/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 1h 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 15years and above. Three sputum specimens were submitted as spot–early morning–spot. An additional specimen (Xs) was submitted 1h 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