Liquid vs. solid culture for tuberculosis: Performance and cost in a resource-constrained setting
International Journal of Tuberculosis and Lung Disease
Aurum Institute for Health Research, Private Bag X 30500, Houghton, Johannesburg, 2041, South Africa; London School of Hygiene and Tropical Medicine, London, United Kingdom
SETTING: National Health Laboratory Services tuberculosis (TB) laboratory, South Africa. OBJECTIVES: To compare Mycobacterium Growth Indicator Tube (MGIT) with Löwenstein-Jensen (LJ) medium with regard to Mycobacterium tuberculosis yield, time to positive culture and contamination, and to assess MGIT cost-effectiveness. DESIGN: Sputum from gold miners was cultured on MGIT and LJ. We estimated cost per culture, and, for smear-negative samples, incremental cost per additional M. tuberculosis gained with MGIT using a decision-tree model. RESULTS: Among 1267 specimens, MGIT vs. LJ gave a higher yield of mycobacteria (29.7% vs. 22.8%), higher contamination (16.7% vs. 9.3%) and shorter time to positive culture (median 14 vs. 25 days for smear-negative specimens). Among smear-negative samples that were culture-positive on MGIT but negative/contaminated on LJ, 77.3% were non-tuberculous mycobacteria (NTM). Cost per culture on LJ, MGIT and MGIT+LJ was respectively US$12.35, US$16.62 and US$19.29. The incremental cost per additional M. tuberculosis identified by standard biochemical tests and microscopic cording was respectively US$504.08 and US$328.10 using MGIT vs. LJ, or US$160.80 and US$109.07 using MGIT+LJ vs. LJ alone. CONCLUSION: MGIT gives higher yield and faster results at relatively high cost. The high proportion of NTM underscores the need for rapid speciation tests. Minimising contaminated cultures is key to cost-effectiveness. © 2010 The Union.
adult; aged; article; bacterium culture; bacterium identification; cost effectiveness analysis; decision tree; female; human; major clinical study; male; Mycobacterium tuberculosis; priority journal; South Africa; sputum culture; comparative study; cost; culture medium; economics; follow up; growth, development and aging; isolation and purification; microbiological examination; microbiology; middle aged; Mycobacterium fortuitum; prevalence; reproducibility; retrospective study; sputum; standards; tuberculosis; young adult; Adult; Aged; Bacteriological Techniques; Costs and Cost Analysis; Culture Media; Follow-Up Studies; Humans; Middle Aged; Mycobacterium fortuitum; Prevalence; Reproducibility of Results; Retrospective Studies; South Africa; Sputum; Tuberculosis; Young Adult; culture medium; Adult; Aged; Bacteriological Techniques; Costs and Cost Analysis; Culture Media; Follow-Up Studies; Humans; Middle Aged; Mycobacterium fortuitum; Prevalence; Reproducibility of Results; Retrospective Studies; South Africa; Sputum; Tuberculosis; Young Adult