Investigated
What are proxy measures versus true outcomes?
Short answer
Image: annualreviews.org
A proxy measure is an observable indicator used in place of the outcome that ultimately matters, often because it is faster, cheaper, or easier to measure. A true outcome—also called a final, clinical, or patient-important outcome—directly reflects the effect or condition of interest. Proxies can be useful, but changes in them do not automatically imply changes in the true outcome.
The views on this question
Two lenses on the same evidence. Source weight and the primary source ratio show what each rests on.
Skeptics
Source weight 60%Lens adapted to this topic: Critical cases against treating proxies as outcomes
The critical perspective emphasizes that measurement precision is not the same as validity. A proxy can omit important dimensions of the underlying construct, distort causal estimates, or become detached from the goal when people optimize the metric itself. This view does not reject proxies outright; it argues that researchers and decision-makers should test the proxy–outcome relationship, examine sensitivity to measurement quality, and avoid treating correlation as equivalence.
- A precisely measured proxy can still fail to answer the question if it captures only part of the intended construct.
- Poor construct validity can materially change estimated relationships and leave misleading associations in place.
- A change in an intermediate biomarker may not translate into a benefit—and can potentially diverge from patient-important outcomes.
- When a measure is made the target, strategic behavior can weaken its connection to the underlying goal, as in teaching to standardized tests.
- Proxy selection should be accompanied by explicit assumptions, validation, and sensitivity analysis rather than relying on labels or correlation alone.
Follow the white rabbit
Deeper threads worth pulling on next.
- When do proxies mislead clinical decisions?Different angle, same storyHistorical cases in cardiology and oncology show relying on surrogates can harm patients and misdirect care.
- How are surrogate endpoints validated?Different angle, same storyRegulatory science explains the statistical and evidentiary tests for proving a surrogate predicts true outcomes.
- What are perverse incentives from proxies?