Table 4.
Overview clinical effect estimates of QALY model for the missing data methods
| RA | CCA (% bias) | MI-PMM (% bias) | Log MI-PMM (% bias) | Two-step MI (% bias) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| M | M + H | M | M + H | M | M + H | M | M + H | M | M + H | |
| 17 % Missing data | ||||||||||
| n | 237 | 193 | 201 | 154 | 237 | 193 | 237 | 193 | 237 | 193 |
| Mean (QALY) | 0.730 | 0.798 | 0.722 | 0.798 | 0.728 | 0.792 | 0.727 | 0.791 | 0.728 | 0.792 |
| SE mean (QALY) | 0.015 | 0.016 | 0.017 | 0.016 | 0.016 | 0.016 | 0.016 | 0.016 | 0.020 | 0.016 |
| QALY difference | 0.054 | 0.060 (11) | 0.061 (12) | 0.061 (12) | 0.061 (12) | |||||
| SE QALY difference | 0.018 | 0.020 (12) | 0.020 (10) | 0.020 (10) | 0.020 (11) | |||||
| z for CCA and t for MI | 2.970 | 2.950 | 3.020 | 3.020 | 3.000 | |||||
| p value | 0.003 | 0.003 | 0.003 | 0.003 | 0.003 | |||||
| 95 % CI lower limit | 0.018 | 0.020 | 0.021 | 0.021 | 0.021 | |||||
| 95 % CI upper limit | 0.090 | 0.100 | 0.100 | 0.100 | 0.100 | |||||
| 35 % Missing data | ||||||||||
| n | 237 | 193 | 163 | 122 | 237 | 193 | 237 | 193 | 237 | 193 |
| Mean (QALY) | 0.730 | 0.790 | 0.715 | 0.790 | 0.718 | 0.790 | 0.717 | 0.791 | 0.718 | 0.790 |
| SE mean (QALY) | 0.015 | 0.018 | 0.020 | 0.018 | 0.017 | 0.016 | 0.017 | 0.016 | 0.017 | 0.016 |
| QALY difference | 0.054 | 0.068 (24) | 0.069 (27) | 0.071 (30) | 0.069 (27) | |||||
| SE QALY difference | 0.018 | 0.023 (27) | 0.021 (17) | 0.022 (18) | 0.022 (20) | |||||
| z for CCA and t for MI | 2.970 | 2.910 | 3.230 | 3.260 | 3.150 | |||||
| p value | 0.003 | 0.004 | 0.001 | 0.001 | 0.002 | |||||
| 95 % CI lower limit | 0.018 | 0.022 | 0.027 | 0.028 | 0.026 | |||||
| 95 % CI upper limit | 0.090 | 0.113 | 0.111 | 0.113 | 0.112 | |||||
| 50 % missing data | ||||||||||
| n | 237 | 193 | 132 | 91 | 237 | 193 | 237 | 193 | 237 | 193 |
| Mean (QALY) | 0.730 | 0.782 | 0.717 | 0.782 | 0.705 | 0.785 | 0.708 | 0.784 | 0.706 | 0.784 |
| SE mean (QALY) | 0.015 | 0.021 | 0.021 | 0.021 | 0.018 | 0.017 | 0.018 | 0.018 | 0.018 | 0.018 |
| QALY difference | 0.054 | 0.047 (13) | 0.077 (41) | 0.074 (36) | 0.075 (38) | |||||
| SE QALY difference | 0.018 | 0.026 (43) | 0.024 (29) | 0.024 (30) | 0.024 (31) | |||||
| z for CCA and t for MI | 2.970 | 1.820 | 3.260 | 3.110 | 3.140 | |||||
| p value | 0.003 | 0.069 | 0.001 | 0.002 | 0.002 | |||||
| 95 % CI lower limit | 0.018 | −0.004 | 0.031 | 0.027 | 0.028 | |||||
| 95 % CI upper limit | 0.090 | 0.098 | 0.123 | 0.120 | 0.122 | |||||
M refers to the methadone maintenance treatment group, M + H refers to the group that had medical co-prescription of heroin. SE standard error, QALY quality of life years gained, CI confidence interval, RA reference analysis, CCA complete case analysis, PMM multiple imputation with predictive mean matching, Log MI-PMM multiple imputation with predictive mean matching on log-transformed costs, Two-step-MI two-step multiple imputation with predictive mean matching