Obtaining hospital and physician participation in a case-control study of colon cancer

This paper describes efforts to solicit hospital and physician participation for a case-control study of the etiology of colon cancer in the five Pennsylvania counties of the Philadelphia metropolitan area. Forty-seven of the 70 hospitals in this region were eligible for inclusion in the study. Thirty-seven (79%) agreed to participate, 27 of them within six months of initial contact. The median time to approval of participation was three months and the median number of separate contacts was nine. At least five participating hospitals submitted the protocol to their lawyers and nine required that special procedures be developed for release of patient information. Two hundred fourteen of 256 listed attending physicians were eligible for participation; 161 (75%) permitted all patients to be contacted; 23 (11%) permitted some patients to be contacted; 30 (14%) refused all patient contact. A significant association between type of specialty and type of permission was found (p~.005). Concerns about confidentiality and lack of personal advantage were frequently cited by non-participants. The validity of case-control studies relying on hospital or physician ascertainment of cases is seriously challenged by such lengthy delays and lack of participation which can result in a biased pool of potential cases.