Placebo-adjusted effect: difference between revisions
Diff·revision 1 → 2·05:45, 15 Oct 2024
Difference between revision 1 and revision 2 of Placebo-adjusted effect. 6 lines changed; the page grew by 881 bytes.
| Revision 1 — 09:00, 7 Oct 2024 DiagramDelphine (talk) create article — trial programme stub 1,276 bytes +1,276 | Revision 2 — 05:45, 15 Oct 2024 DrTitration (talk) add the PMID 2,157 bytes +881 | ||
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| 10 | The active-arm change alone conflates the treatment effect with everything else operating during the trial: regression to the mean, the natural course of the condition, the lifestyle intervention both arms received, and the effects of being observed.{{r|hrobjartsson2010}} | 10 | The active-arm change alone conflates the treatment effect with everything else operating during the trial: regression to the mean, the natural course of the condition, the lifestyle intervention both arms received, and the effects of being observed.{{r|hrobjartsson2010}} |
| 11 | 11 | ||
| + | 12 | == What the comparator arm captures == | |
| + | 13 | A placebo arm in a modern obesity trial is not a no-treatment arm. Participants receive the same lifestyle counselling, the same visit schedule and the same measurement, and the difference between the arms is the treatment alone.{{r|hrobjartsson2010,ich_e10}} | |
| + | 14 | ||
| + | 15 | Several distinct phenomena contribute to the change in a placebo arm. Regression to the mean operates because participants are enrolled at a moment when their measurement was high enough to qualify. The trial's own intervention — diet advice, activity advice, regular weighing — has an effect. Observation changes behaviour. And the natural course of a condition may be towards improvement or deterioration.{{r|hrobjartsson2010}} | |
| + | 16 | ||
| 12 | == References == | 17 | == References == |
| 13 | {{reflist}} | 18 | {{reflist}} |
| 14 | <ref name="ich_e9">International Council for Harmonisation, ''E9(R1): Estimands and Sensitivity Analysis in Clinical Trials'' (2019).</ref> | 19 | <ref name="ich_e9">International Council for Harmonisation, ''E9(R1): Estimands and Sensitivity Analysis in Clinical Trials'' (2019).</ref> |
| 15 | <ref name="hrobjartsson2010">Hróbjartsson A, Gøtzsche PC. "Placebo interventions for all clinical conditions." ''Cochrane Database of Systematic Reviews'' (1):CD003974 (2010). PMID 20091554.</ref> | 20 | <ref name="hrobjartsson2010">Hróbjartsson A, Gøtzsche PC. "Placebo interventions for all clinical conditions." ''Cochrane Database of Systematic Reviews'' (1):CD003974 (2010). PMID 20091554.</ref> |
| + | 21 | <ref name="ich_e10">International Council for Harmonisation, ''E10: Choice of Control Group and Related Issues in Clinical Trials'' (2000).</ref> | |
| 16 | 22 | ||
| 17 | {{DEFAULTSORT:Placebo-adjusted effect}} | 23 | {{DEFAULTSORT:Placebo-adjusted effect}} |