For theoutreachintervention, the eight neighborhoods were paired by county location (SF or CC) and similarities in their race/ethnic composition. In San Francisco one member of two pairs was selected at random for the intervention and the other as a control.
Health Center 4 in San Francisco’s Chinatown was heavily utilized and unable to accept an additional clinic load that might have resulted from new referrals for screening and any needed follow-up. It was therefore allocated to the control condition. In Contra Costa it was necessary to select Richmond for the intervention and Pittsburg for the control for logistical reasons For the inreach intervention, the eight clinics were paired by county, number of annual outpatient visits,and the estimated race/ethnic composition of the patients. One member of the pair was selected for the intervention, while the other served as a control. Complete random allocation of the clinics for intervention was not feasible because the infrastructure of the Contra Costa Clinics would not support development of the planned computer-based reminder system. Therefore, two of the four clinic pairs in San Francisco were randomly assigned to the intervention, but the two Contra Costa Clinics had to be assigned to the control condition.
The remaining San Francisco clinics, to which the Contra Costa clinics were paired, were assigned to the intervention. Thus, two clinics and surrounding neighborhoods were selected for both outreach and inreach interventions, and two were designated as control for both interventions; likewise, two clinics each were either selected for the outreach but not for the inreach intervention or vice versa (Fig. 1).