Table 3.
Expected costs of diagnostic algorithms
| 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 |
Abbreviations: MGIT Mycobacterial Growth Indicator 960 automated liquid culture system, DST Drug Susceptibility Testing using MGIT SIRE system.
* 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.
**Utilizes current estimates of Xpert and MTBDRplus sensitivity and specificity and prevalence of TB and drug-resistant TB in South Africa.