Clinical Study
Pharmacodynamics Must Inform Statistics: An Example from a Cocaine Dependence Pharmacotherapy Trial
Table 2
Systolic and diastolic blood pressure results as a function of inclusion of baseline as a covariate in the statistical model.
| Parameter | Analysis not including baseline as a covariatea | Analysis with baseline as a covariatea | Estimate | SE | 95% confid. limits | | | Estimate | SE | 95% confid. limits | | |
| Systolic blood pressure | Intercept | 124.80 | 1.74 | 121.38–128.21 | 71.66 | <0.0001 | 28.10 | 6.67 | 15.0–41.19 | 4.20 | <0.0001 | Baseline | NA | NA | NA | NA | NA | 0.78 | 0.05 | 0.67–0.88 | 14.51 | <0.0001 | Medication | −3.54 | 2.24 | −7.94–0.86 | −1.58 | 0.11 | −4.16 | 1.37 | −6.84–1.48 | −3.04 | 0.002 | Week | 0.01 | 0.13 | −0.26–0.27 | 0.01 | 0.99 | −0.0193 | 0.13 | −0.28–0.24 | −0.15 | 0.88 | Med by week | 0.02 | 0.19 | −0.36–0.40 | 0.09 | 0.93 | 0.02 | 0.19 | −0.37–0.39 | 0.07 | 0.94 |
| Diastolic blood pressure | Intercept | 79.33 | 1.28 | 76.82–81.84 | 61.84 | <0.0001 | 20.59 | 4.26 | 12.25–28.94 | 4.84 | <0.0001 | Baseline | NA | NA | NA | NA | NA | 0.74 | 0.05 | 0.64–0.84 | 13.99 | <0.0001 | Medication | −2.91 | 1.66 | −6.16–0.34 | −1.75 | 0.08 | −3.03 | 1.06 | −5.11– −0.96 | −2.87 | 0.004 | Week | −0.04 | 0.11 | −0.25–0.17 | −0.38 | 0.70 | −0.04 | 0.11 | −0.25–0.16 | −0.42 | 0.67 | Med by week | −0.03 | 0.16 | −0.35–0.28 | −0.18 | 0.85 | −0.05 | 0.16 | −0.36–0.26 | −0.30 | 0.76 |
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Data from study weeks 1–12 included in analysis.
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