Table IV.
Longitudinal model parameter estimates. IPSS: summary International Prostate Symptom Score, IRT: Item response theory. Relative standard errors were obtained in NONMEM
| IPSS model | Unidimensional IRT model | |||
|---|---|---|---|---|
| Parameter | Value | Relative standard error (%) | Value | Relative standard error (%) |
| Baseline | 19.6 | 1.7 | 0.0283 | 146.3 |
| Pmax (maximal placebo response) | − 4.12 | 9.9 | − 1.03 | 10.9 |
| Tprog (placebo half-life) | 15.3 | 18.8 | 12.3 | 20.5 |
| Drug effect | − 1.98 | 19.2 | − 0.542 | 20.3 |
| Baseline Box-Cox shape | 1.87 | 41.7 | 0.373 | 25.4 |
| Drift Box-Cox shape | 39.3 | 47.6 | - | - |
| Covariates | ||||
| Baseline QoL on Pmax | 0.208 | 13.2 | - | - |
| Baseline BII on Baseline | 0.0211 | 19.6 | 0.121 | 17.9 |
| Baseline QoL on Baseline | 0.0873 | 12.7 | 0.325 | 17.4 |
| Region on Baseline | − 0.0803 | 26 | − 0.338 | 24.1 |
| Interindividual variability (IIV) | ||||
| IIV Baseline | 13.7% | 8.3 | 75.9% | 7.7 |
| IIV Pmax | 121.7% | 15.4 | 128.5% | 15.4 |
| IIV Drift | 1.8% | 19.4 | 0.7% | 8.8 |
| IIV Tprog | 90.6% | 12 | 52.4% | 9.9 |
| IIV Baseline-Pmax correlation | - | - | 1.7% | |
| IIV Baseline-Drift correlation | - | - | 9.2% | |
| IIV Pmax-Drift correlation | 43.1% | 34% | ||
| Residual error | ||||
| Proportional residual error | 10.9% | 8.9 | ||
| Additive residual error | 189.2% | 6.7 | ||