Diagnostic accuracy of the microscopic observation drug susceptibility assay: a pilot study from India
Abstract:SETTING: The microscopic observation drug susceptibility (MODS) assay is a rapid, sensitive, low-cost liquid culture technique.
OBJECTIVE: To establish the accuracy of MODS for the detection of active pulmonary tuberculosis (TB), and to document the costs and challenges of setting up this assay in a low-income setting.
DESIGN: Prospective blinded pilot study of 200 adult TB suspects at a tertiary referral hospital in India. Reference standard included culture (Löwenstein-Jensen and automated liquid culture) and clinical diagnosis.
RESULTS: Patients were mostly male (n = 122, 61.1%) and out-patients (n = 184, 92.0%), with a mean age of 40.4 years (standard deviation 16.2). Seventeen (8.5%) were human immunodeficiency virus infected and 47 (23.5%) were reference culture-positive. Compared to reference culture, MODS was 78.9% sensitive (95%CI 62.2–90.0) and 96.7% specific (95%CI 92.0–98.8). Clinical assessment suggested that MODS was false-negative in 3/8 reference culture-positive MODS-negatives and true-positive in 4/6 reference culture-negative MODS-positives. MODS was faster than solid (P < 0.001) and liquid culture (P = 0.088), and cheaper than both.
CONCLUSION: MODS may be a good alternative to automated liquid culture, but there were several challenges in setting up the assay. Prior training and validation, setup costs and inability to rule out cross-contamination need to be taken into account before the test can be established.
Document Type: Regular Paper
Affiliations: 1: Department of Microbiology, Christian Medical College, Vellore, Tamil Nadu, India 2: Department of Medicine, Christian Medical College, Vellore, Tamil Nadu, India 3: Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India 4: Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada
Publication date: April 1, 2010
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