Commentary on Cox CL, Lensing S, Rai SN et al. Proxy assessment of quality of life in pediatric clinical trials: Application of the Health Utilities Index 3. Qual Life Res 2005; 14: 1045–1056

The paper by Cox et al. offers an important potential for informing designs of future studies. The rates of missing measurements in the study are much greater than those reported by other investigators. This is not surprising because the nurse assessors were restricted explicitly by the study protocol from collecting required information, had little contact with many of the patients, and some had a poor understanding of the measurement system. …