Table 1.
Parameters included in uncertainty analysis
| Parameter | Baseline valuea | Baseline perioda | Prior distribution | Prior mean, standard deviation | 95% CI | |
|---|---|---|---|---|---|---|
| 1. | HIV counselling and testing | |||||
| 1.1 Annual rate of first-time HIV testing in non-pregnant HIV-negative women at age 25 | 0.30 | 2011/12 | Gamma (17.36, 69.4) | 0.25, 0.06 | 0.15–0.38 | |
| 1.2 Ratio of male HCT uptake to female HCT uptake at age 25 (HIV negative, non-pregnant) | 0.68 | 2011/12 | Gamma (94.4, 138.8) | 0.68, 0.07 | 0.55–0.82 | |
| 1.3 Time to the introduction of home-based HCT (in years after 2014/15) | – | – | Weibull (0.195, 0.55) | 33.1, 65.1 | 0–21+b | |
| 1.4 Annual rate of HIV testing through home-based HCT | – | – | Gamma (5.44, 15.56) | 0.35, 0.15 | 0.12–0.70 | |
| 1.5 Time to the introduction of intensified counselling for positives (in years after 2014/15) | – | – | Weibull (0.195, 0.55) | 33.1, 65.1 | 0–21+b | |
| 1.6 Coverage of intensified risk reduction counselling (of diagnosed HIV positives) | – | – | Uniform (0, 1) | 0.50, 0.29 | 0.03–0.98 | |
| 1.7 Reduction in unprotected sex following intensified counselling in HIV-positive adults | – | – | Beta (2.083, 2.083) | 0.50, 0.22 | 0.10–0.90 | |
| 2. | Adult ART | |||||
| 2.1 Percentage of patients starting ART with CD4 <200 who are virally suppressed (VL <400 copies/ml) | 0.77 | 2012/13 | Beta (10.5, 3.136) | 0.77, 0.11 | 0.52–0.94 | |
| 2.2 Time to the introduction of universal ART eligibility (in years after 2014/15) | – | – | Weibull (0.195, 0.55) | 33.1, 65.1 | 0–21+b | |
| 2.3 Time to the introduction of POC CD4 testing (in years after 2014/15) | – | – | Weibull (0.195, 0.55) | 33.1, 65.1 | 0–21+b | |
| 2.4 Fraction starting ART immediately after diagnosis if POC CD4/universal ART available | 0.40 | 2012/13 | Beta (13.8, 9.2) | 0.60, 0.10 | 0.40–0.79 | |
| 2.5 Mean time to women starting ART if ART is not started at time of diagnosis (in months) | 20 | 2013/14 | Gamma (5.06, 0.281) | 18.0, 8.00 | 5.9–36.7 | |
| 3. | Behaviour change | |||||
| 3.1 Average partner age difference in non-marital relationships | 3.00 | 2011/12 | Gamma (9, 3) | 3.00, 1.00 | 1.37–5.25 | |
| 3.2 Ratio of marriage rates in 2016/17 to those in 2011/12 | 1.00 | 2011/12 | Gamma (25, 25) | 1.00, 0.20 | 0.65–1.43 | |
| 3.3 Ratio of sexual debut rates in 2016/17 to those in 2011/12 | 1.00 | 2011/12 | Gamma (25, 25) | 1.00, 0.20 | 0.65–1.43 | |
| 3.4 Odds of condom use in marital relationships (relative to 1998) | 1.78 | 2011/12 | Gamma (14.97, 8.41) | 1.78, 0.46 | 1.00–2.79 | |
| 3.5 Odds of condom use in non-marital relationships (relative to 1998) | 3.14 | 2011/12 | Gamma (4.89, 1.56) | 3.14, 1.42 | 1.00–6.47 | |
| 3.6 Odds of condom use in SW–client relationships (relative to 1998) | 3.80 | 2011/12 | Gamma (3.84, 1.01) | 3.80, 1.94 | 1.00–8.44 | |
| 4. | Prevention of mother-to-child transmission | |||||
| 4.1 Rate of retesting in late pregnancy | 0.45 | 2011/12 | Beta (9.02, 3.01) | 0.75, 0.12 | 0.48–0.94 | |
| 4.2 Fraction of newly diagnosed pregnant women who start ART prior to delivery | 0.75 | 2011/12 | Beta (49.73, 5.525) | 0.90, 0.04 | 0.81–0.96 | |
| 4.3 Proportionate increase in mean duration of ART prior to delivery (relative to pre-2010) | 0.50 | 2011/12 | Gamma (25, 35.71) | 0.70, 0.14 | 0.45–1.00 | |
| 4.4 Relative rate of short-course antiretroviral uptake if long-term ART not started prior to delivery | 1.00 | 2012/13 | Uniform (0, 1) | 0.50, 0.29 | 0.03–0.98 | |
| 4.5 Relative infectivity of HIV-positive women on long-term ART (breastfeeding) | 0.20 | 2011/12 | Beta (3.00, 12.00) | 0.20, 0.10 | 0.05–0.43 | |
| 4.6 Median duration of EBF in months, if EBF is initiated | 2.00 | 2010/11 | Gamma (16, 4) | 4.00, 1.00 | 2.29–6.00 | |
| 4.7 Fraction of mothers discontinuing EBF who stop breastfeeding completely | 0.30 | 2010/11 | Beta (5.16, 29.25) | 0.15, 0.06 | 0.05–0.28 | |
| 5. | Medical male circumcision | |||||
| 5.1 Annual probability of MMC uptake in men in non-marital relationships | 0.15 | 2013/14 | Beta (1.880, 4.387) | 0.30, 0.17 | 0.04–0.68 | |
| 6. | Pre-exposure prophylaxis | |||||
| 6.1 Effectiveness of PrEP | – | – | Beta (1.27, 1.9) | 0.40, 0.24 | 0.03–0.88 | |
| 6.2 Proportionate reduction in condom usage in PrEP users | – | – | Beta (0.8, 7.2) | 0.10, 0.10 | 0.00–0.37 | |
| 6.3 Time to the introduction of PrEP for sex workers (in years after 2014/15) | – | – | Weibull (0.195, 0.55) | 33.1, 65.1 | 0–21+b | |
| 6.4 Time to the introduction of PrEP for youth aged 15–24 (in years after 2014/15) | – | – | Weibull (0.195, 0.55) | 33.1, 65.1 | 0–21+b | |
| 6.5 Annual rate at which sex workers adopt PrEP if it is available | – | – | Gamma (2.25, 7.50) | 0.30, 0.20 | 0.04–0.80 | |
| 6.6 Annual rate at which sexually active youth adopt PrEP if it is available | – | – | Gamma (2.25, 7.50) | 0.30, 0.20 | 0.04–0.80 | |
a
No baseline value or baseline period is specified for parameters that relate to interventions not yet introduced in South Africa.
b
A delay of more than 20 years means that the intervention is not introduced over the period considered in this analysis; hence the upper limit of the distribution is irrelevant. ART=antiretroviral treatment, EBF=exclusive breastfeeding, HCT=HIV counselling and testing, MMC=medical male circumcision, PrEP=pre-exposure prophylaxis, POC=point of care, SW=sex worker, VL=viral load.