Cost-Efficient Multiply Matched Case-Control Study Designs

Abstract

In multiply matched case-control studies, a number of cases and controls may be included in each matched set. However, when per-participant costs between cases and controls differ, investigators should be aware of how the numbers of cases and controls per matched set affect the overall total study cost. Traditional statistical approaches to designing case-control studies do not account for study costs. Given an effect size, the power to detect differences is typically a function of the numbers of cases and controls within each matched set. Therefore, the same level of statistical power will be achieved based on various combinations of the numbers of cases and controls. Typical matched case-control studies match a case to a number of controls by levels of 1 or more known factors. Several authors have shown that for study designs with 1 case per matched set, the optimal number of controls within each matched set that minimizes the total study cost is the square root of the ratio of the cost of a case to the cost of a control. Herein, we extend this result to the setting of a multiply matched case-control study design, when 1 or more cases are matched to controls within each matched set. A Shiny web application implementation of the proposed methods is presented.

Keywords: case-control studies; matched case-control studies; observational studies; research costs.

Figure 1

Expected total study cost (equation 3) for various cost ratios . The asterisk (*) indicates the optimal set (d^*, m^*). The total cost is . The cost ratios shown are = 2.0 (A), = 3.0 (B), = 4.0 (C), and = 5.0 (D).