Review Question - QID 103900

Recall bias occurs when study participants who have developed the disease of interest are more likely to report the exposure of interest.

Observational studies are more sensitive to sources of bias than randomized controlled trials, and retrospective studies even more so than prospective designs. One of the drawbacks of retrospective studies is the potential for recall bias. By definition, in retrospective studies the exposure status of participants has already occurred at the time that case/control (i.e. diseased vs. non-diseased) status is determined. Participants are human, and as such their memories are not infallible. When patients are diagnosed with an illness as severe as mesothelioma, they may be motivated to look for a reason. Even unintentional suggestions by study investigators about a potential cause may cause participants to be more likely to remember (or misremember) that they had been exposed. Therefore, the proportion of cases which report the exposure may be higher than among controls irrespective of the true rate of exposure among the two groups.

Greenberg et al. describe the etiology of recall bias. Patients who have a serious disease may search their memory for an exposure in an attempt to explain or to understand why they acquired the illness. Control subjects, who do not have the disease, may be less likely to remember an exposure because it has less meaning and is less important to them.

Levine et al. describe methods by which to avoid or mitigate recall bias. As in the present example, blinding the interviewers to the case/control status of the participants protects against the interviewers probing more deeply for the exposure status. This does not, however, protect against the increased motivation of cases to recall the exposure themselves. Using standardized criteria by which to ascertain the exposure can mitigate this. Ideally, the ascertainment of the exposure would be done not by the patient's own memory, but by external and objective confirmation, e.g. blood tests or workplace safety reports.

Incorrect Answers:
Answer 1: Blinding of the interviewers protects against interviewers consciously or unconsciously altering or interpreting the results of the interview in a systematic manner.
Answer 3: The fact that mesothelioma status initially determines the case/control status of participants does not allow for observer bias.
Answer 4: Lead-time bias is usually associated with studies in which early diagnosis gives the false impression of improved time to event.
Answer 5: Retrospective studies are never free of potential bias, and this study in particular is sensitive to recall bias.