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Table 3 Expected costs of diagnostic algorithms

From: Comparison of laboratory costs of rapid molecular tests and conventional diagnostics for detection of tuberculosis and drug-resistant tuberculosis in South Africa

Algorithm Cost per sample Incremental cost
Implementation of conventional diagnostics versus molecular testing   
Fluorescence microscopy plus liquid culture testing scenario* on all sputa $16.88 reference
Xpert MTB/RIF alone on all sputa $14.93 $-1.95
MTBDRplus alone on all sputa $23.46 $6.58
Intensive implementation of molecular tests in combination with conventional diagnostics   
Xpert MTB/RIF plus liquid culture testing scenario* on all sputa $28.41 $11.53
MTBDRplus plus liquid culture testing scenario* on all sputa $36.94 $20.06
Conventional diagnostics with selective implementation of molecular tests   
Fluorescence microscopy plus liquid culture testing scenario* on all sputa + Xpert MTB/RIF on smear-positive sputa $18.37 $1.49
Fluorescence microscopy plus liquid culture testing scenario* on all sputa + MTBDRplus on smear-positive sputa $19.23 $2.35
Fluorescence microscopy on all sputa plus a) Xpert MTB/RIF on smear-positive sputa and b) liquid culture on smear-negative sputa with Xpert MTB/RIF on culture positive isolates $16.51 -$0.37
Fluorescence microscopy on all sputa plus a) MTBDRplus on smear-positive sputa and b) liquid culture on smear-negative sputa with MTBDRplus on culture positive isolates $17.75 $0.87
Molecular testing with selective implementation of culture and dst**   
Xpert MTB/RIF on all sputa, with liquid culture testing scenario* on sputa with a positive molecular test $16.86 $-0.02
MTBDRplus on all sputa, with liquid culture testing scenario* on sputa with a positive molecular test $25.39 $8.51
  1. Abbreviations: MGIT Mycobacterial Growth Indicator 960 automated liquid culture system, DST Drug Susceptibility Testing using MGIT SIRE system.
  2. * Liquid culture testing scenario consists of sputum processing and MGIT culture, followed by Ziehl Neelsen smear microscopy on positive cultures, anti-MPB64 assays on cultures with mycobacterial growth, and MGIT SIRE DST on cultures with growth of M. tuberculosis.
  3. **Utilizes current estimates of Xpert and MTBDRplus sensitivity and specificity and prevalence of TB and drug-resistant TB in South Africa.