EVALUATION OF SPUTUM SMEARS CONCENTRATED BY CYTOCENTRIFUGATION FOR DETECTION OF ACID-FAST BACILLI

Early identification and isolation of tuberculosis patients is of utmo st importance to minimize the risk of further epidemic spread of the d isease. The traditional concentrated acid-fast smears are not very rel iable tools for the presumptive diagnosis of tuberculosis. Acid-fast b acillus (AFB) smears from 120 patient specimens and 80 simulated AFB s amples were processed according to standard laboratory procedures and by cytocentrifugation (Cyto-Tek, Ames Division, Miles Laboratories, In c., Elkhart, Ind.). Prior to dispensing of samples into the Cyto-Tek c hambers, specimens were liquefied and decontaminated by mixture with a n equal volume of 5% sodium hypochlorite (household bleach). Culture a nd smear results were correlated. Of 120 patient specimens, 43 were cu lture and smear negative by both methods. Ten specimens were overgrown with mold and bacteria, but 2 of them had positive AFB smears by cyto centrifugation only. There were 67 positive AFB cultures, with 67 posi tive cytocentrifuge smears and 34 positive smears by the conventional technique. Of the 80 simulated positive AFB samples, all grew mycobact eria on culture. Smears from the 10(5)- to 10(3)-CFU/ml specimens were positive by both methods. The simulated samples with 10(2) CFU/ml yie lded smears positive only by cytocentrifugation. The Cyto-Tek AFB smea rs had a greater correlation with positive culture than did the smears from concentrated specimens. The sensitivity, efficiency, and rapidit y of the Cyto-Tek AFB smear technique resulted in increased detection of mycobacteria in clinical specimens. The simplicity and safety of th is method will enable qualified mycobacteriology technologists to rapi dly and accurately perform sputum smears for AFB at clinics, emergency rooms, and field sites, as well as in the traditional laboratory sett ing.