Comparison of microscopic positivity in smears from sputa stained according to Ziehl-Neelsen in different modifications.
Some basic factors influencing the detection of microscopic positivity in the sputa of patients with tuberculosis of the lungs, stained according to Ziehl-Neelsen in various modifications, were studied in 9 laboratories in 5 different countries (Bulgaria, Czechoslovakia, Mongolia, German Democratic Republic and Poland). Each laboratory prepared 200 coded slides from 50 suspect-positive sputa. The slides were stained using four different methods and despatched, without examination, to the next laboratory in the series. A total of 1 800 slides from 450 sputa were thus evaluated and each smear was successively examined by 8 different readers. The study has shown that the result of direct microscopy depends primarily on the individual qualities and attentiveness of the workers evaluating the slides while the remaining factors are less important. Mechanical homogenization of sputa before making the smear, carried out by shaking the sputum with glass beads, had a significant effect on the number of detected mycobacteria while homogenization using soda lye did not influence the positivity in any direction. The detection of mycobacteria after hot staining was significantly higher than after a 2-hour action of carbolfuchsin without heating. Additional staining with picric acid or malachite green had no effect on the amount of bacteria detected and the method of examination (in one line or meander-like on selected spots) was found to be completely unimportant.
D006801:Humans; D008722:Methods; D013183:Sputum / Q000382:microbiology*; D013194:Staining and Labeling; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000382:microbiology*