[Quality of sputum microscopy in the network of tuberculosis bacteriology laboratories in Colombia]

The objective of this study was to evaluate the technical quality of sputum microscopy carried out for diagnostic purposes in the Network of Tuberculosis Bacteriology Laboratories in Colombia. The National Central Reference Laboratory received 6,529 slides for reexamination from the network of 513 sectional, regional, and local laboratories, which contributed 33.2%, 27.6%, and 39.2%, respectively, of the slides. These included all the positive (3,283) and negative (3,246) smears processed during a 4-month period. The reexamination was carried out by six laboratory workers who did not know the origin of the slides or the original diagnosis. When qualitative problems were detected, a second reexamination was done, which significantly increased the percentage of agreement for both the positive results (93.9%) and the negative (98.7%). Overall, the level of agreement was 96.3%. A significant correlation was found (P < 0.05) between good slide preparation and staining and agreement in the readings, as well as between thin smears, presence of fuchsin precipitates, and deficient coloration and conflicting readings (P < 0.05). The highest percentages of agreement were associated with laboratories that performed the largest number of sputum examinations each month (96.5%), and with readings done by experienced, university-trained bacteriologists (96.6%). It is concluded that indirect technical supervision and ongoing training of laboratory personnel are important determinants of the impact of the tuberculosis control program.