Invited commentary: Recall bias in melanoma -- much ado about almost nothing?

Recall bias has been given considerable attention in textbooks and methodological research because of its potential to jeopardize the validity of epidemiologic results. Case-control studies on self-reported ultraviolet radiation exposure as a risk factor for melanoma have been described as especially prone to the deleterious effect of recall bias because of the growing public awareness about these risks. Using an ideal test-retest design in a large nested case-control study, Parr et al. (Am J Epidemiol. 2009;169(3):257-266) examined to what extent recall bias in melanoma risk factors is actually identifiable and which consequences its presence has on effect estimates of these risk factors. They found only minor indications of recall bias, showing an inconsistent overall pattern and a quite negligible effect on risk estimates. Recall bias was not observed in those exposures where it was most expected (solarium use and other ultraviolet radiation-related exposures). Their findings cannot be used as an argument that future case-control studies in melanoma epidemiology should be avoided because of the biasing effect of recall bias.