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Quality assessment of smear microscopy by stratified lot sampling of treatment follow-up slides

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Abstract
SETTING: Ten peripheral laboratories performing routine acid-fast bacilli (AFB) smear microscopy in Lima, Peru. OBJECTIVES: To test whether external quality assessment (EQA) rechecking of AFB smears becomes more efficient with stratified lot sampling of treatment follow-up smears. DESIGN: In 2 consecutive years, a stratified lot sample of 36 treatment follow-up slides and 24 diagnostic slides were randomly selected and blindly rechecked. A second controller determined the final result for discordant slides. Feedback was provided to laboratory technicians during supervisory visits. RESULTS: More false-negative errors were found in the follow-up slides than in the tuberculosis suspect slides: 25 vs. 3. This represented a yield of 3.5% in 720 follow-up slides and only 0.6% in 480 diagnostic slides. Positive predictive values were high in both years. Respectively three and eight laboratories did not reach a relative sensitivity of >65% during the first and second year, and a clear improvement was seen in only one laboratory. Excessive workload seemed to preclude raising the level of routine performance. CONCLUSIONS: EQA with stratified lot sampling of treatment follow-up slides proved very efficient and effective for identifying laboratories with substandard performance in a setting with low positivity rates in routine diagnostic smears.
Keywords
quality control, diagnosis, sputum smear microscopy, tuberculosis, BLINDED RECHECKING, ACID-FAST BACILLI, FLUORESCENCE MICROSCOPY, SPUTUM, TUBERCULOSIS, DIAGNOSIS, YIELD, TB

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Citation

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Chicago
Otero, L, A Van Deun, J Agapito, R Ugaz, G Prellwitz, E Gotuzzo, and Patrick Van Der Stuyft. 2011. “Quality Assessment of Smear Microscopy by Stratified Lot Sampling of Treatment Follow-up Slides.” International Journal of Tuberculosis and Lung Disease 15 (2): 211–216.
APA
Otero, L, Van Deun, A., Agapito, J., Ugaz, R., Prellwitz, G., Gotuzzo, E., & Van Der Stuyft, P. (2011). Quality assessment of smear microscopy by stratified lot sampling of treatment follow-up slides. INTERNATIONAL JOURNAL OF TUBERCULOSIS AND LUNG DISEASE, 15(2), 211–216.
Vancouver
1.
Otero L, Van Deun A, Agapito J, Ugaz R, Prellwitz G, Gotuzzo E, et al. Quality assessment of smear microscopy by stratified lot sampling of treatment follow-up slides. INTERNATIONAL JOURNAL OF TUBERCULOSIS AND LUNG DISEASE. 2011;15(2):211–6.
MLA
Otero, L, A Van Deun, J Agapito, et al. “Quality Assessment of Smear Microscopy by Stratified Lot Sampling of Treatment Follow-up Slides.” INTERNATIONAL JOURNAL OF TUBERCULOSIS AND LUNG DISEASE 15.2 (2011): 211–216. Print.
@article{2023783,
  abstract     = {SETTING: Ten peripheral laboratories performing routine acid-fast bacilli (AFB) smear microscopy in Lima, Peru. 
OBJECTIVES: To test whether external quality assessment (EQA) rechecking of AFB smears becomes more efficient with stratified lot sampling of treatment follow-up smears. 
DESIGN: In 2 consecutive years, a stratified lot sample of 36 treatment follow-up slides and 24 diagnostic slides were randomly selected and blindly rechecked. A second controller determined the final result for discordant slides. Feedback was provided to laboratory technicians during supervisory visits. 
RESULTS: More false-negative errors were found in the follow-up slides than in the tuberculosis suspect slides: 25 vs. 3. This represented a yield of 3.5% in 720 follow-up slides and only 0.6% in 480 diagnostic slides. Positive predictive values were high in both years. Respectively three and eight laboratories did not reach a relative sensitivity of >65% during the first and second year, and a clear improvement was seen in only one laboratory. Excessive workload seemed to preclude raising the level of routine performance. 
CONCLUSIONS: EQA with stratified lot sampling of treatment follow-up slides proved very efficient and effective for identifying laboratories with substandard performance in a setting with low positivity rates in routine diagnostic smears.},
  author       = {Otero, L and Van Deun, A and Agapito, J and Ugaz, R and Prellwitz, G and Gotuzzo, E and Van Der Stuyft, Patrick},
  issn         = {1027-3719},
  journal      = {INTERNATIONAL JOURNAL OF TUBERCULOSIS AND LUNG DISEASE},
  keywords     = {quality control,diagnosis,sputum smear microscopy,tuberculosis,BLINDED RECHECKING,ACID-FAST BACILLI,FLUORESCENCE MICROSCOPY,SPUTUM,TUBERCULOSIS,DIAGNOSIS,YIELD,TB},
  language     = {eng},
  number       = {2},
  pages        = {211--216},
  title        = {Quality assessment of smear microscopy by stratified lot sampling of treatment follow-up slides},
  url          = {http://www.ingentaconnect.com/content/iuatld/ijtld/2011/00000015/00000002/art00013},
  volume       = {15},
  year         = {2011},
}

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