Costs, life years saved and incremental cost-effectiveness ratios associated with screening strategies in the base-case scenario
| 15-year cost (US$)* | Life years saved† | Cost effectiveness | ICER (life years) | |||
| Discounted§ | Undiscounted | Societal perspective | Provider perspective | |||
| Base-case scenario, 0–2-year-old cohort, QTF | ||||||
| No testing | 2477 | 10.43 | 13.05 | 237 | ||
| TST | 3513 | 9.52 | 11.90 | 369 | (Dominated) | (Dominated) |
| QFT after (+) TST | 3909 | 9.51 | 11.88 | 411 | (Dominated) | (Dominated) |
| QFT after (–) TST | 4563 | 10.39 | 13.00 | 439 | (Dominated) | (Dominated) |
| QFT | 4891 | 9.88 | 12.35 | 495 | (Dominated) | (Dominated) |
| Base-case scenario, 3–5-year-old cohort, QTF | ||||||
| No testing | 1483 | 10.56 | 13.21 | 140 | ||
| TST | 2251 | 9.73 | 12.17 | 231 | (Dominated) | (Dominated) |
| QFT after (+) TST | 2793 | 9.71 | 12.16 | 288 | (Dominated) | (Dominated) |
| QFT after (–) TST | 3147 | 10.57 | 13.22 | 298 | 233516 | 162192 |
| QFT | 3535 | 9.87 | 12.35 | 358 | (Dominated) | (Dominated) |
| Base-case scenario, 0–2-year-old cohort, TSPOT | ||||||
| No testing | 2610 | 10.45 | 13.08 | 250 | ||
| TST | 3718 | 9.52 | 11.90 | 391 | (Dominated) | (Dominated) |
| TSPOT after (+) TST | 4180 | 9.51 | 11.89 | 440 | (Dominated) | (Dominated) |
| TSPOT after (–) TST | 4934 | 10.42 | 13.03 | 474 | (Dominated) | (Dominated) |
| TSPOT | 5317 | 9.89 | 12.37 | 538 | (Dominated) | (Dominated) |
| Base-case scenario, 3–5-year-old cohort, TSPOT | ||||||
| No testing | 1483 | 10.56 | 13.21 | 140 | ||
| TST | 2251 | 9.73 | 12.17 | 231 | (Dominated) | Rank |
| TSPOT after (+) TST | 2893 | 9.71 | 12.16 | 298 | (Dominated) | Order |
| TSPOT after (–) TST | 3294 | 10.57 | 13.22 | 312 | 254243 | Changes‡ |
| TSPOT | 3717 | 9.91 | 12.41 | 375 | (Dominated) | |
↵* This value represents the 15-year cost per child. Cost data were collected in South African Rand; results were then converted to US$ (US$1 = 7.2 South African Rand, 2009 annual average).
↵† This value represents the life years saved per child over the course of 15 years and reflects a South African life expectancy of 49 years for men and 53 years for women.31
§Discounting at 3% annually is conventionally applied in cost-effectiveness analysis. Future costs and outcomes are discounted to account for time preference. Discounting makes current costs and benefits worth more than those occurring in the future because there is an opportunity cost to spending money now and there is desire to enjoy benefits now rather than in the future. The reason why current spending incurs an opportunity cost relative to delayed spending is that a monetary investment yields a real rate of return and therefore there is a cost to spending money in the present.
↵‡ Rank order of test changes to: (1) no testing; (2) TST; (3) TSPOT after positive TST; (4) TSPOT; (5) TSPOT after negative TST. The no-testing strategy continues to dominate the TST, the TSPOT after positive TST, and the TSPOT strategies. The TSPOT after negative TST strategy becomes most effective and is associated with an ICER of $232 351 compared with the no-testing strategy.
ICER, incremental cost-effectiveness ratio; QFT, QuantiFERON; TSPOT, T-SPOT.TB; TST, tuberculin skin test.