New health professions after a decade and a half: delegation, productivity and costs in primary care.

Though knowledge about physician's assistants and nurse practitioners is far from conclusive, these new health practitioners (NHPs) appear to perform a large percentage of primary care services at a high level of quality and productivity. Moreover, the gap between the physician/NHP substitution ratio and the NHP/physician cost ratio seems wide enough to assure cost savings when NHPs are used well.