Association between assessments of AFB microscopy and sputum smear from the lot quality assurance sampling (LQAS) program.

Abstract

The lot quality assurance sampling (LQAS) program is acid-fast bacilli (AFB) microscopy quality control to recheck results as stated in the guideline of World Health Organization (WHO). The assessments report the percent of agreement rate which is not less than 90% and there must be no major error with the percent acceptable smear which is not less than 80% of each characteristic including pattern, quality, staining, cleanliness, thickness, size and evenness. The purpose of this cross- sectional study was to investigate the association between the assessments of AFB staining in various smears from hospitals in the upper central region of Thailand. The 73 slides containing errors (major errors and minor errors) and 400 slides of correct assessments were defined. The results showed that the assessments are significantly associated with cleanliness (p-value <0.010). The percentage of correct assessment of poor cleanliness  was found to be decreased (64.5%) while the percentage of major error of poor cleanliness was increased (29.0%), and the association was similar to that of the size of the sputum smear (p-value <0.010). There was a decrease in percentage of correct assessment of smaller sputum slides (73.8%) while the percentage of major error of smaller group is increased (23.1%).  If the preparation of sputum smear is clean and appropriately sized, the occurrence of error assessments will be reduced.  This will give reliable AFB staining result for tuberculosis diagnosis.