Health economic impact of patients with phenylketonuria (PKU) in France - A nationwide study of health insurance claims data.

Background: Phenylketonuria (PKU) is an inherited metabolic disease. If left untreated, it can lead to severe irreversible intellectual disability and can cause seizures, behavior disturbance, and white matter disease. This study aimed at evaluating the health economic impact of patients with PKU in France.

Methods: This retrospective observational study used health insurance claims data from the French SNDS (Système National des Données de Santé) database, which contains data from over 66 million French inhabitants. Patients with PKU were identified by ICD-10 diagnosis codes E70.0 (PKU) and E70.1 (Other hyperphenylalaninemia) documented as a chronic condition (affection de longue durée - ALD) or in the inpatient setting in the SNDS database between 2006 and 2018. Patients with PKU were matched to controls without PKU by age, sex, and region. Patients with early- and late-diagnosed PKU were defined as patients born after and before the implementation of nationwide newborn screening in France in 1972, respectively. Outcomes were analyzed for the year 2018.

Results: Overall, 3549 patients with PKU were identified in the database on January 1st, 2018. Of those, 3158 patients versus 15,703 controls with at least one healthcare consumption in 2018 were available for outcome analyses. Patients with PKU had 7.7 times higher healthcare costs than non-PKU controls in 2018 (€11,144 versus 1456 mean costs;  < 0.0001). Pharmaceutical costs including dietary amino acid supplements were the cost driver and contributed 80.0% of the overall mean difference (MD) between patients with PKU and matched non-PKU controls. More than half (52.4%) of the mean pharmaceutical costs per patient with PKU was attributable to medical foods including dietary amino acid supplements.Of the 3158 patients with PKU, 2548 (80.7%) were classified as early-diagnosed and 610 (19.7%) as late-diagnosed. Increased healthcare costs, in comparison to non-PKU controls, were more evident in early-diagnosed patients (€11,263 versus €855 mean costs; 13.2-fold increase;  < 0.0001). For patients with late-diagnosed PKU, healthcare costs were 2.7-fold higher compared to matched non-PKU controls (€10,644 versus €3951 mean costs; p < 0.0001). Outpatient pharmaceutical costs accounted for 89.1% of the MD between early-diagnosed patients and controls. Among late-diagnosed patients, 55.5% of the MD were attributable to costs for inpatient care, followed by costs for outpatient care (23.9%) and outpatient pharmaceutical costs (20.6%).

Conclusion: The results indicate that PKU is associated with substantially increased health care costs compared to non-PKU controls in France. The health economic impact was most evident in patients with early-diagnosed PKU due to increased outpatient pharmaceutical costs, especially for medical foods including dietary amino acid supplements. For late-diagnosed and by definition older patients with PKU, the excess costs compared with matched controls were mostly driven by costs for inpatient care.