Reproducibility of sputum smear examination for acid-fast bacilli: practical problems met during cross-checking

• Published in: The international journal of tuberculosis and lung disease Vol. 3; no. 9; pp. 823 - 829
• Main Authors: VAN DEUN, A, ROORDA, F. A, CHAMBUGONJ, N, HYE, M. A, HOSSAIN, M. A
• Format: Journal Article
• Language: English
• Published: Paris, France IUATLD 01.09.1999; Union internationale contre la tuberculose et les maladies respiratoires
• Subjects: Bangladesh; Biological and medical sciences; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Mycobacterium; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Quality Control; Reproducibility of Results; Specimen Handling; Sputum - microbiology; Staining and Labeling; Stains And Staining; Tropical medicine; Tuberculosis, Pulmonary - diagnosis; Bangladesh; Performance evaluation; Human; Lung disease; Respiratory disease; Lung; Cross validation; Mycobacterial infection; Bacteriological investigation; Infection; Direct method; Microbiological investigation; Tuberculosis; Reproducibility; Laboratory investigations; Quality control; Sputum; Bacteriosis; Smear; Technique
• ISSN: 1027-3719; 1815-7920

SETTING: A TB control programme in Bangladesh with proficiency testing of sputum smears for acid-fast bacilli (AFB) using cross-checking of routine smears.OBJECTIVE: To document factors that may adversely affect repeatability of the AFB smear, and which should be taken into account for interpretation of cross-checking.DESIGN: A number of simple experiments falling within the scope of small routine laboratories in a developing country.RESULTS: Fuchsin staining is not stable, fading quickly in direct sunlight and combinations of high temperature and humidity. Diffuse daylight, immersion oil or xylene did not have the same effect. Contamination of smears by saprophytic mycobacteria may occur during staining or rinsing, with contaminants becoming visible only after restaining and cross-checking. Finally, AFB may be dislodged from smears during soaking in xylene or restaining, especially if the smears are made from thin, liquefied sputum.CONCLUSIONS: These possible interfering factors should be taken into account when organizing proficiency testing and interpreting its results.