Background: Blinded rechecking of auramine-stained acid-fast bacilli (AFB) sputum smears using fluorescence microscopy (FM), especially FM using light-emitting diode (LED), is not well understood.
Objective: To examine the rechecking of auramine-stained sputum smears without restaining within a month using LED FM.
Methods: A total of 4799 centrifuged smears of sputum samples were stained by the auramine phenol method and examined using LED FM; 564 systematically selected smears were subjected to blinded rechecking without restaining by controllers. The initial results of the readers were compared to those of the controllers. Discrepancies were resolved by a referee. The quality of LED FM was assessed by the referee using the culture result as gold standard.
Results: Among the rechecked smears, one high false-negative error was made by a reader, while one high false-positive error and 19 high false-negative errors were made by the controllers. The errors were resolved by culture. Smear results for 18 slides were not available due to AFB fading.
Conclusion: AFB colour fading using LED FM, which affected the accurate evaluation of blinded rechecking of AFB smears without restaining within a month, is confirmed in this large study.