Patient recruitment--European perspective.

A considerable number of patients have to be recruited in a clinical trial to obtain solid results. In pediatric studies, patient recruitment is frequently problematic. In the simple common childhood illnesses, the number of recruitable patients is certainly large, but they may be hard to reach, and the imbalance between potential benefit and inconvenience of participation may reduce motivation to enroll. In severe diseases, the balance may be right, but the available number of patients may be small. Good communication with the child and family, as well as the motivation of colleagues to admit, is another key element in success. Proper study design, including realistically identified sources of patients, reasonable inclusion, and exclusion criteria, also are required.