Use of an interrupted time-series design to evaluate a cancer screening program.

An alternative approach to intervention-control designs to evaluate community health education studies is to use a quasi-experimental design in which the outcomes of interest are examined over time in the intervention unit. The Forsyth County Cancer Screening Project (FoCaS) was a comprehensive clinic- and community-based education program to increase screening for cervical cancer and breast cancer among low-income women. This paper reports the use of piecewise regression accounting for potential effects of auto-correlation in the data to evaluate the effectiveness of the project in increasing mammography screening. Data for the evaluation of trends in screening consisted of all mammograms performed during the period of May 1992 through June 1995 at the Reynolds Health Center in Forsyth County, North Carolina. The results suggested that the FoCaS project was effective in increasing mammography screening among women age 40 or older in the study population. Analysis of the trends by age indicated that the program had differential effects on women age 40-49 and 50 or older. The results demonstrate that analyses of the type presented here can either complement or serve as an alternative to more traditional intervention-control analyses.