In a systematic review of aspirin as a possible preventive of lung cancer (Feskanich et al., British Journal of Cancer, 2007
Http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2360462/pdf/6603996a.pdf), the
Authors identified all papers with original data that assessed the relation between
Aspirin use and lung cancer incidence or mortality (N=18) and then excluded:
- Retrospective analyses (N=4)
- Prospective studies that did not account for smoking (N=3)
- Studies with no quantitative measure of aspirin use (N=2).
Which of the following statements are true? (select all that apply)
A)The results of the review will be biased because 9 of the 18 studies were excluded
B)It is appropriate to exclude retrospective studies because of potential biases in aspirin recall and selection of controls
C)It is appropriate to exclude retrospective studies because their results are likely to be confounded
D)It is inappropriate to exclude the retrospective studies because there is only a small number of studies overall
E)It is appropriate to exclude studies with no control for confounding by smoking because this is likely to influence the association between aspirin and lung cancer

Question

Quizplus · Accepted Answer

It is highly likely that the results of retrospective studies could be
biased due to selection bias and/or recall bias (B) and it is also likely that smoking and
aspirin use could be associated making smoking a likely confounder (E).Confounding is
no more a problem in retrospective studies than prospective studies (C) and study
designs that are very likely to give biased results should be excluded regardless of how
many potentially eligible studies were identified (D).After excluding the studies with
potentially biased results, the results of the review should be more reliable (A).

In a Systematic Review of Aspirin as a Possible Preventive