Assessing non-medical outcomes of screening presents constant challenges. Marteau and colleagues¹ offer some insight into the complexities of assessing non-medical outcomes in their study of abdominal aortic aneurysm (AAA) screening. The paper reports that self assessed health (SAH) was lower among men who were found to have an aortic aneurysm than men who did not, yet baseline measurement indicated that much of this difference pre-dated screening. Poorer SAH seemed to predict having an aortic aneurysm. The authors suggest that the findings have implications for the methods used to assess psychological impact of screening tests and warn us not to erroneously conclude that poorer outcomes are necessarily a product of screening, if baseline differences are not assessed.

Marteau et al’s¹ findings are extremely interesting and raise important issues for the assessment of psychosocial or quality of life (QOL) outcomes in the screening context. Adequate assessment of psychosocial as well as medical outcomes, is crucially important, especially given the potential of screening to detect inconsequential disease^2–4 but presents many challenges. These have received comparatively little attention. We have identified three main methodological concerns: (1) the need for a control group (preferably created by randomisation); (2) the need for baseline and follow up measurements; (3) the need for reliable measurement tools with high criterion and content validity.

The first concern, obtaining an adequate control group, perhaps presents the most difficulty. If our goal is to assess the impact of screening we need to measure the combined impact of the screening procedure, follow up tests, and treatments. The best way to achieve this is to randomise people to be screened or not screened and to measure the psychosocial impact on everyone at multiple times (see fig …