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Journal of Clinical Microbiology, October 2008, p. 3325-3329, Vol. 46, No. 10
0095-1137/08/$08.00+0     doi:10.1128/JCM.01175-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Poor Performance of Universal Sample Processing Method for Diagnosis of Pulmonary Tuberculosis by Smear Microscopy and Culture in Uganda

Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, California,¹ HIV/AIDS Division, University of California, San Francisco, California,² Department of Medicine, Faculty of Medicine, Makerere University, Kampala, Uganda,³ Uganda Ministry of Health, Kampala, Uganda,⁴ Makerere University-University of California San Francisco Research Collaboration, Kampala, Uganda,⁵ Department of Medical Microbiology, Faculty of Medicine, Makerere University, Kampala, Uganda,⁶ Department of Epidemiology and Biostatistics, University of California, San Francisco, California⁷

Received 20 June 2008/ Returned for modification 1 August 2008/ Accepted 7 August 2008

Laboratory methods to improve smear microscopy are an urgent priority for global tuberculosis control. The novel universal sample processing (USP) method has been reported to improve conventional diagnostic testing for tuberculosis while also providing inhibitor-free specimens for molecular assays. However, no studies evaluating the method in the field have been conducted. In this study, we compared the performance of the USP method to that of the standard N-acetyl-L-cysteine-NaOH (NALC) method for conventional diagnosis of tuberculosis in 252 adults admitted to Mulago Hospital in Kampala, Uganda, with a clinical suspicion of pneumonia. A single early-morning sputum specimen collected from each patient was divided into two aliquots, each of which was assigned a random identification number. One randomly numbered specimen was processed by the USP method and the other by the NALC method. Mycobacterial cultures were more frequently negative in USP compared to NALC specimen aliquots (58% versus 43%; P < 0.001). There was no difference in the proportion of contaminated mycobacterial cultures (12% versus 11%; P = 0.87). The sensitivity and specificity of smear microscopy for the USP method were 52% and 86%, respectively, and were not significantly different from those for the NALC method (56% and 86%, respectively) using mycobacterial culture results as a reference standard. These results suggest that the USP method did not provide any significant advantage over the standard NALC method for conventional diagnosis of tuberculosis in our setting and illustrate the importance of well-designed, field-level evaluations of novel diagnostic techniques.

Published ahead of print on 13 August 2008.