Theory 97/Selection & Bias/Case-control studies
Recall Follows the Diagnosis
The claim
Recall of exposure is biased by the diagnosis itself, so cases report exposures differently from controls even when true exposure is equal.
01Mechanism
A diagnosis prompts search for causes; cases scrutinise their history more than controls, raising reported exposure.
02Prediction
Reported exposure should exceed records more in cases.
03Refutation
Equal recall accuracy would remove the bias.