Control response proportions in population-based case-control studies in Germany.

We investigated the methods of recruitment, levels and determinants of response, and the calculation method of response proportions in population-based case-control studies in Germany. We identified 26 eligible studies. The pooled analysis showed that the response proportion was 68% among controls and 80% among cases. Response proportions among controls without telephones were about 50% lower than for controls with telephones. We propose a new measure that indicates the efficacy of the recruitment strategy.