Table 4.
Results of univariate sensitivity analyses
| Sensitivity analysis | Universal psychological ICER (95% UI) AU$ per DALY averted |
Indicated psychological ICER (95% UI) AU$ per DALY averted |
Indicated bibliotherapy ICER (95% UI) AU$ per DALY averted |
|---|---|---|---|
| Baseline model | 7350 (dominates – 23 070) | 19 550 (3081–56 713) | N/A |
| (1) No cost offsets | 11 993 (4483–28 137) | 24 220 (7608–61 106) | N/A |
| (2) Time and travel costs | N/A | 48 694 (11 154–146 530) | N/A |
| (3) Assume a 50% school participation rate | 7537 (dominates – 24 561) | 18 345 (2993–56 837) | N/A |
| (4) Model non-significant intervention effect sizes & extrapolate health benefits using an exponential decay rate | 1118 (dominates – 32 801) | 6671 (dominates – 29 980) | Dominates* (dominates* – 3594) |
| (5) Model effect sizes based on RCTs using structured clinical interviews only | Dominates (dominates – 4000) | 17 889 (2214–58 953) | N/A |
| (6) Model intervention effect sizes based on RCTs using an ITT analysis only | 15 521 (dominates – 41 658) | 20 783 (3012–64 316) | N/A |
| (7) Calculate the weighted average disability weight by using an alternative severity distribution based on DSM-IV algorithms for mild, moderate and severe depression | 4723 (dominates – 15 509) | 11 951 (1805–34 862) | N/A |
| (8a) Using the standard gamble utility weight (direct valuation) | 5403 (dominates – 19 513) | 11 294 (1791–48 375) | N/A |
| (8b) Using the EQ-5D utility weight (indirect valuation) | 3983 (dominates – 13 465) | 10 721 (1476–32 133) | N/A |
| (9a) Internet-delivered intervention pathway, assuming it is unmoderated and has 100% efficacy relative to face-to-face prevention interventions | 4890 (553–14 398) | Dominates (dominates – 3076) | N/A |
| (9b) Internet-delivered intervention pathway, assuming it is unmoderated and has 50% efficacy relative to face-to-face prevention interventions | 14 657 (5779–34 273) | 1698 (dominates – 10 186) | N/A |
| (9c) Internet-delivered intervention pathway, assuming it is clinician-moderated and has 100% efficacy relative to face-to-face prevention interventions | 113 960 (42 370–243 209) | 8711 (dominates – 30 536) | N/A |
| (9d) Internet-delivered intervention pathway, assuming it is clinician-moderated and has 50% efficacy relative to face-to-face prevention interventions | 227 922 (93 124–467 802) | 23 153 (4060–63 650) | N/A |
| (10a) Discount rate of 0% for health benefits and 3% for intervention costs | 7154 (3–24 070) | 18 751 (2799–54 418) | N/A |
| (10b) Discount rate of 6% for health benefits and 3% for intervention costs | 8503 (dominates – 25 277) | 20 187 (2720–59 167) | N/A |
| (10c) Discount rate of 3% for health benefits and 0% for intervention costs | 7430 (dominates – 24 641) | 19 081 (dominates – 58 970) | N/A |
| (10d) Discount rate of 3% for health benefits and 6% for intervention costs | 7771 (185–24 225) | 19 888 (2969–59 960) | N/A |
95% UI, 95% uncertainty interval; EQ-5D, EuroQol-5-dimension; ICER, incremental cost-effectiveness ratio; ITT, intention-to-treat; N/A, not applicable; RCT, randomised control trial.
*
A sizeable proportion of uncertainty iterations for indicated bibliotherapy lie in both the northwest and southeast quadrants of the cost-effectiveness plane – signifying that there is a dual likelihood of indicated bibliotherapy being either a dominating or dominated intervention.