Evaluation of sputum smears concentrated by cytocentrifugation for detection of acid-fast bacilli

Abstract

Early identification and isolation of tuberculosis patients is of utmost importance to minimize the risk of further epidemic spread of the disease. The traditional concentrated acid-fast smears are not very reliable tools for the presumptive diagnosis of tuberculosis. Acid-fast bacillus (AFB) smears from 120 patient specimens and 80 simulated AFB samples were processed according to standard laboratory procedures and by cytocentrifugation (Cyto-Tek, Ames Division, Miles Laboratories, Inc., Elkhart, Ind.). Prior to dispensing of samples into the Cyto-Tek chambers, specimens were liquefied and decontaminated by mixture with an equal volume of 5% sodium hypochlorite (household bleach). Culture and smear results were correlated. Of 120 patient specimens, 43 were culture and smear negative by both methods. Ten specimens were overgrown with mold and bacteria, but 2 of them had positive AFB smears by cytocentrifugation only. There were 67 positive AFB cultures, with 67 positive cytocentrifuge smears and 34 positive smears by the conventional technique. Of the 80 simulated positive AFB samples, all grew mycobacteria on culture. Smears from the i0to 103-CFU/ml specimens were positive by both methods. The simulated samples with 102 CFU/ml yielded smears positive only by

Detection of infection or infectious agents by use of cytologic and histologic stains

“…Traditionally, specimens are concentrated by centrifugation (with aerosol-free sealed centrifuge cups) for at least 15 min at Ն3,000 ϫ g (149). Recently, Saceanu et al reported that for sputum specimens from a selected group of patients, the sensitivity of AFB microscopy with the Kinyoun stain was greatly improved by using cytocentrifugation for smear preparation (154). This finding, however, was not confirmed in a more extensive evaluation in which auramine O was used for visualization of AFB (201).…”

Navigating Through Laboratory Reports: Expectations, Dreams, and Realities

“…It has been shown that concentration of the sputum by cytocentrifugation can lead to detection of AFB in a smear close to 100% for culture-positive specimens. 7 The laboratory report on the smear examination should indicate whether the smear was made from raw or processed sputum and whether it was examined with light or fluorescence microscopy. The laboratories report the results as the average number of AFB per microscopy field, or as 4+ for more than 9 AFB per field, 3+ for 1 to 9 AFB per field, 2+ for 1 to 9 AFB per 10 fields, and 1+ for 1 to 9 AFB per 100 fields.…”

Effect of Relative Centrifugal Forces and Centrifugation Times on Recovery of Mycobacterium Tuberculosis

“…However, direct sputum microscopy has a low sensitivity often not more than 20 to 65%, in comparison with culture. [2,4] Further, the increasing frequency of smearnegative pulmonary TB cases could be due to the low sensitivity of the direct AFB smear. However, culture detects 10-100 bacilli /ml of sputum ensuring the isolation of tubercle bacilli more effectively than direct smear microscopy.…”

“…[1] However, the prevalence and further epidemic of TB and other mycobacterial infections may be considerably minimized by detecting the disease in the early stage. [2] Global tuberculosis control programs uses microscopic examination for detection of Acid Fast bacilli (AFB). [3] However, sputum direct microscopy has low sensitivity.…”