Selvakumar, N and Govindan, Dakshayani and Chandu, Naik Ashok and Frieden, T R and Narayanan, P R
(2003)
Processing Sputum Specimens in a Refrigerated Centrifuge Does Not
Increase the Rate of Isolation of Mycobacterium tuberculosis.
Journal of Clinical Microbiology, 41 (1).
pp. 469-471.
ISSN Print: 0095-1137; Online: 1098-660X
Abstract
A total of 1,047 sputum samples from pulmonary tuberculosis patients was collected in cetyl pyridinium
chloride-sodium chloride solution. Each sample was divided into two parts and randomly allocated for the
isolation of Mycobacterium tuberculosis, with one part to be processed by the standard method and the other by
a modified method. In the standard method, the samples were processed by using nonrefrigerated centrifuges,
while in the modified method, they were processed by using a refrigerated centrifuge. Fifty-seven samples that
yielded contaminants were excluded, and the remaining 990 samples were taken up for analysis. The rates of
isolation of M. tuberculosis with the standard and modified methods were 48.6 and 48.1%, respectively, and the
difference was not statistically significant (McNemar’s test; P > 0.5). However, 51% of the positive cultures
were isolated within 2 weeks with the modified method compared to 37% with the standard method (chi-square
test; P < 0.001). The results of the study reveal that processing of sputum samples in a refrigerated centrifuge
does not improve the rate of isolation but will result in rapid isolation of M. tuberculosis.
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