Table 1.
Inputs and source data for simulation model to project budget impact of expanded HIV screening to public payers
| Variable | Base Case (Range) | Sources |
|---|---|---|
| General | ||
| Discount rate | 0% | (13) |
|
| ||
| Number of HIV-negative individuals who will be screened, at start of simulation | ||
| Na | 50,100,000 (upper 55,100,000) | See appendix |
|
| ||
| Characteristics of prevalent cases aware of their infection b | ||
| Na | 711,000 (upper 747,000) | See appendix |
| Age (mean) | 41 years | (60) |
| Female | 30% | (25, 60) |
| CD4 at simulation entry (mean, std) | 390 (260) cells/mm3 | (60) |
| Viral load | Published natural history data | (61), see appendix |
| Prior OI experience | Published natural history data | (61), see appendix |
|
| ||
| Characteristics of prevalent cases unaware of their infection c | ||
| Na | 189,000 (upper 198,000) |
See appendix |
| Age (mean) | 41 years | (60) |
| Female | 30% | (60) |
| CD4 at simulation entry (mean, std) | Published natural history data | (61, 62), see appendix |
| Viral load | Published natural history data | (61), see appendix |
| Prior OI experience | None | Assumption |
|
| ||
| Characteristics of incident cases d | ||
| Na | 45,800 per year (upper 48,100) | See appendix |
| Age (mean) | 33 years | (63), see appendix |
| Female | 30% | (42) |
| CD4 at simulation entry (mean, std) | 534 (164) cells/mm3 | (62) |
| Viral load | >100,000 copies/mL | Assumption, see appendix |
| Prior OI experience | None | Assumption, see appendix |
|
| ||
| Test characteristics | ||
| Probability of monthly test receipt | ||
| Current practice (%) | 0.83% (0%-1.67%) | (45) |
| Expanded (%) | 1.67% (0.83%-8.33%) | See text |
| Probability detected case linked to caree |
80% (50%-100%) | (36, 49, 50) |
| Rapid test characteristics | ||
| Sensitivity pre-seroconversion | 0.1% | Calculated |
| Specificity pre-seroconversion | 99.6% | (64) |
| Specificity post-seroconversion | 99.9% | (64) |
| HIV-positive test return rate | 97% (90%-100%) | (48) |
| HIV-negative test return rate | 97% (90%-100%) | (48) |
| ELISA test characteristics | ||
| Sensitivity pre-seroconversion | 0.1% | Calculated |
| Sensitivity post-seroconversion | 99.6% | (65) |
| Specificity pre-seroconversion | 99.9% | (65) |
| HIV-positive test return rate | 75% (50%-100%) | (48) |
| HIV-negative test return rate | 67% (50%-100%) | (48) |
|
| ||
| Testing costs | ||
| HIV test kit, administration, and laboratory analysis | ||
| Rapid test | $12.23 | (33) |
| ELISA | $7.05 | (33) |
| Confirmatory testing for positive results | ||
| Rapid test | $44.28 | (33) |
| ELISA | $52.72 | (33) |
| Pre-test counseling | $0 ($7.76) | (33) |
| Post-test counseling for negative test result |
$7.53 | (33) |
| Post-test linkage and counseling for positive test result |
$14.61 | (33) |
| Administrative cost for non-return for results |
$9.02 | Assumption (0.5 hours of administrative staff time and $1.00 for mail and phone reminders) |
All calculations exclude individuals eligible for testing and care through the Veterans Administration or private insurance.
Aware is defined as aware of their infection and currently in care through discretionary or entitlement programs, at the start of the simulation.
Unaware is defined as being unaware of their infection at the start of the simulation, and only eligible for government-financed care upon detection.
Incident cases are uninfected at the start of the simulation, and are only eligible for government-financed care upon detection.
See technical appendix for a more detailed description of the linkage to care probability and the test return rate.