Tuberc Respir Dis.  1974 Sep;21(3):149-155. 10.4046/trd.1974.21.3.149.

An Experimental Study of Direct Smear Examinations for Detecting Patients with Pulmonary Tuberculosis

• KMID: 2529012
• DOI: http://doi.org/10.4046/trd.1974.21.3.149

Abstract

Evaluations of three various techniques of smear preparation were made. Also the results of microscopic reading at various numbers of fields were compared to obtain an optimal number of fields for effective reading. These procedures were studied since they are basic diagnostic tools in tuberculosis laboratory work. 1) Smear preparations by the wire-loop methed (WLS), the wooden-applicator method(WAS) and the slide press-down method, were thoroughly compared to evaluate. i. Safety during work. ii. simplicity (Convenience) and, iii. Discovery rates. 2) From 50 up to 500 microscopic fields were read on negative slides and one-plus positive slides to obtain disco very rates. In the case of one-plus slides, the results of the 150 fi eld-reading were employed as a obtain the cumulative number of bacilli by the criterion to number of microscopic fields increased.
Results
obtained in the study were as follows. 1. Of the three methods concerned in the smear preparation study, both the wire-loop method and the wooden-applicator method( with a few drawbacks) were found to have yielded the best results in many respects, whereas the slide press-down method showed less accurate results as well as even some health safety risks in the smear preparation . The slide press-down method showed some unfavorable responses from microscopists concerning its accuracy and also most felt that the procedure was unsafe and not widely practiced in this country. 2. On the basis of the results obtained from the prolonged microscopy on smears, the 300-field reading yielded the appearance of nearly twice as many tubercle bacilli as the 150- field reading. Therefore , smears considered presumably negative must be read at more than 300 microscopic fields in the tuberculosis Iaboratories.