Table 2. Comparison of algorithm characteristics for previous HIV-positive testers and previous HIV-negative/unknown testers at Zuckerberg San Francisco General Hospital (ZSFG), January -November 2015.
| RT-IF1 (Jan – Aug, 2015) | AR-MS-VL2 (Sep – Nov, 2015) | |||
|---|---|---|---|---|
| All testers | HIV- /Unknown Testers only | All testers | HIV- /Unknown Testers only | |
| Total # samples tested, N | 16,467 | 16,260 | 5,518 | 5,430 |
| Screened HIV+, N (%) | 292 (1.77) | 85 (0.52) | 115 (2.08) | 27 (0.50) |
| Confirmatory/Supplemental Ab Test, N (%) | ||||
| HIV+ | 217 (74.32) | 35 (41.18) | 88 (76.52) | 11 (40.74) |
| HIV- | 10 (3.42) | 10 (11.76) | 23 (20.00) | 16 (59.26) |
| Indeterminate | 46 (15.75) | 37 (43.53) | 1 (0.87) | 0 (0) |
| Unknown | 19 (6.51) | 3 (3.53) | 3 (2.61) | 0 (0) |
| Final Result,3 N (%) | ||||
| HIV+ | 233 (79.79) | 36 (42.35) | 88 (76.52) | 11 (40.74) |
| HIV- | 56 (27.05) | 46 (54.12) | 25 (21.74) | 14 (51.85) |
| Unknown | 3 (1.03) | 3 (3.53) | 2 (1.74) | 2 (7.41) |
| Status Unresolved by Algorithm,4 N (%) | 65 (22.26) | 40 (47.06) | 11 (9.57) | 6 (22.22)5 |
| Screening PPV, % (95% CI) | 0.81 (0.75-0.85) | 0.44 (0.33-0.55) | 0.78 (0.69-0.85) | 0.44 (0.25-0.65) |
| Screening Specificity, % (95% CI) | 99.65% (99.55-99.74) | 99.72% (99.62-99.79) | 99.54% (99.31-99.69) | 99.74% (99.55-99.85) |
| Hours from first test to result, Median (IQR) | ||||
| Screening test result | 1.98 (1.37,2.65) | 1.9 (1.37,2.6) | 3.43 (2.86,3.98) | 3.4 (2.89,3.99) |
| Confirmatory test result | 40.47 (20.16,56.96) | 41.47 (20.03, 57.60) | 20.30 (17.61, 22.83) | 18.4 (16, 23.15) |
| Final result | 44.47 (21.65, 69.52) | 70.56 (38.35, 300.35) | 20.77 (18.33, 24.11) | 25.67 (18.37, 110.62) |
Uni-Gold HIV Rapid Test (RT) for screening followed by immunofluorescence (IF) confirmation
ARCHITECT® HIV Ag/AB Combo (AR) for screening, followed by Multispot HIV-1/HIV-2 Rapid Test (MS) confirmation, and Abbott RealTime HIV-1assay (VL) as needed for resolution of discrepant results
Final HIV infection status was defined by the algorithm result and any follow-up testing.
For patients who screened RT+, algorithm resolution was defined as either an IF-positive or IF-negative result; IF-indeterminate results required send-out testing were considered unresolved by the algorithm. For patients who screened AR-reactive, algorithm resolution was defined as either an MS-positive result, or an MS-negative with a VL-detected or VL-undetected result; discrepant AR-reactive/MS-negative results without a VL result were considered unresolved by the algorithm.
Additional VL testing confirmed 4/6 to be uninfected