Table 3.
Sensitivity analysis of key model input parameters and baseline assumptionsa.
| Treatment strategy | Undiscounted life expectancy NNRTI → PI (years) | Undiscounted life expectancy PI → NNRTI (years) | Cost-effectiveness ratio ($/year of life saved)a | NNRTI resistance prevalence (%) where cost-effective to use PI → NNRTIb |
|---|---|---|---|---|
| Base case | 8.89 | 7.99 | 910 | 76 |
| ART starting criteria:
CD4 cell count < 350 cells/μl or one opportunistic infectionc |
9.42 | 8.49 | 930 | 76 |
| ART starting criteria:
CD4 cell count < 200 cells/ml or four opportunistic infection or CD4 cell count < 350 cells/μl and one opportunistic infectionc |
8.49 | 7.61 | 890 | 78 |
| First-line ART failure criteria:
CD4 cell count fall of 90% or one opportunistic infectionc |
8.76 | 7.92 | 920 | 65 |
| Rate of CD4 cell count decline | ||||
| + 25% | 8.43 | 7.54 | 910 | 74 |
| − 25% | 9.51 | 8.61 | 920 | 79 |
| Routine care costs | ||||
| + 50% | 8.89 | 7.99 | 1040 | 78 |
| − 50% | 8.89 | 7.99 | 950 | 75 |
| CD4 cell count test costs | ||||
| + 50% | 8.89 | 7.99 | 920 | 76 |
| − 50% | 8.89 | 7.99 | 910 | 76 |
| Discount rate | ||||
| 5% | – | – | 930 | 76 |
| 0% | 8.89 | 7.99 | 880 | 77 |
ART, antiretroviral therapy; CE, cost-effectiveness; PI, protease inhibitor; NNRTI, non-nucleoside reverse transcriptase inhibitor.
In all cases, the cost-effectiveness ratio of the sequence PI + 2NRTI → NNRTI + 2NRTI compared with co-trimoxazole alone is higher than the incremental cost-effectiveness ratio of the NNRTI + 2NRTI → PI + 2NRTI sequence compared with the PI + 2NRTI → NNRTI + 2NRTI. By accepted convention, when this occurs, the cost-effectiveness ratios are reported as ‘dominated’ [8,37]. Thus, the incremental cost-effectiveness ratio reported compares the NNRTI + 2NRTI → PI + 2NRTI sequence to no ART (co-trimoxazole alone).
Applying an incremental cost-effectiveness threshold criteria of three times the per capita gross domestic product for Côte d’Ivoire.
All strategies included co-trimoxazole prophylaxis starting at an observed CD4 cell count < 500/μl. Late-stage severe opportunistic infections included in the base case ART starting subset: severe fungal, isosporiasis, toxoplasmosis, non-tuberculosis mycobacterium, or other severe illnesses.