Population newborn screening for inherited metabolic disease: current UK perspectives.

Some of the generally accepted criteria for screening programmes are inappropriate for newborn metabolic screening as they ignore the family dimension and the importance of timely genetic information. Uncritical application of such criteria creates special difficulties for screening by tandem mass spectrometry, which can detect a range diseases with widely different natural histories and responsiveness to treatment. Further difficulties arise from increasing demands for direct proof of the effects of screening on long-term morbidity and mortality. The randomized controlled trial is held to be the gold standard, but for ethical and practical reasons it will be impossible to achieve for such relatively rare diseases. This approach also oversimplifies the complex matrix of costs and benefits of newborn metabolic screening. A more workable approach could involve Bayesian synthesis, combining quantitative performance data from carefully designed prospective pilot studies of screening with existing experience of the natural history, diagnosis, and management of the individual disorders concerned.