Economic impact of feeding a phenylalanine-restricted diet to adults with previously untreated phenylketonuria.

The aim of the present study was to estimate the direct healthcare cost of managing adults with previously untreated phenylketonuria (PKU) for one year before any dietary restrictions and for the first year after a phenylalanine- (PHE-) restricted diet was introduced. The resource use and corresponding costs were estimated from medical records and interviews with health care professionals experienced in caring for adults with previously untreated PKU. The mean annual cost of caring for a client being fed an unrestricted diet was estimated to be 83 996 pound silver. In the first year after introducing a PHE-restricted diet, the mean annual cost was reduced by 20 647 pound silver to 63 348 pound silver as a result of a reduction in nursing time, hospitalizations, outpatient clinic visits and medications. However, the economic benefit of the diet depended on whether the clients were previously high or low users of nursing care. Nursing time was the key cost-driver, accounting for 79% of the cost of managing high users and 31% of the management cost for low users. In contrast, the acquisition cost of a PHE-restricted diet accounted for up to 6% of the cost for managing high users and 15% of the management cost for low users. Sensitivity analyses showed that introducing a PHE-restricted diet reduces the annual cost of care, provided that annual nursing time was reduced by more than 8% or more than 5% of clients respond to the diet. The clients showed fewer negative behaviours when being fed a PHE-restricted diet, which may account for the observed reduction in nursing time needed to care for these clients. In conclusion, feeding a PHE-restricted diet to adults with previously untreated PKU leads to economic benefits to the UK's National Health Service and society in general.