It has been suggested that controls with adenematous polyps of the colon and rectum should be excluded from case-control studies of cigarette smoking and colorectal cancer.
A claim has been made that the presence of such controls creates a bias toward the null.
The polyps are an intermediate step in a hypothetical causal pathway between the exposure and the disease.
Thus, the recommendation logically extends to the exclusion of all controls who experienced hypothetical causal intermediates from all case-control studies.
It is shown, in the simple case of an exposure that acts solely through the pathway involving the intermediate, that such exclusions create a bias away from the null.
The rationale for recommending the detrimental exclusions appears to stem from a variant of the « trohoc fallacy » : the mistaken view of case-control studies as comparisons between diseased and healthy groups and not as comparisons between groups that differ by exposure.
Mots-clés Pascal : Etude cas témoin, Tumeur maligne, Côlon, Rectum, Tabagisme, Polype, Facteur risque, Epidémiologie, Méthodologie, Homme, Appareil digestif pathologie, Intestin pathologie, Côlon pathologie, Rectum pathologie, Tumeur bénigne
Mots-clés Pascal anglais : Case control study, Malignant tumor, Colon, Rectum, Tobacco smoking, Polyp, Risk factor, Epidemiology, Methodology, Human, Digestive diseases, Intestinal disease, Colonic disease, Rectal disease, Benign neoplasm
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 99-0482255
Code Inist : 002B13B01. Création : 22/03/2000.