Real-world clinical use of large neutral amino acids in phenylketonuria: a nationwide survey from Turkey under reimbursement constraints

Abstract Background Phenylketonuria (PKU) requires lifelong dietary management, and large neutral amino acid (LNAA) supplementation has emerged as a potential adjunct therapy, particularly for individuals with poor dietary adherence. In Turkey, access to LNAA therapy is restricted by reimbursement regulations, which may influence clinical decision-making and patient management. This study aimed to evaluate real-world clinical practices, perceived benefits, and treatment preferences of pediatric metabolic specialists regarding LNAA therapy, with particular attention to reimbursement-related barriers. Methods A descriptive cross-sectional survey was conducted during the 3rd Global Nutricia Metabolics Expert Day (February 2025). Twenty-five pediatric metabolic specialists from 23 centers completed a 13-item questionnaire addressing LNAA experience, prescribing indications, number of treated patients, age at initiation, treatment strategies, perceived benefits, reasons for discontinuation, and preferred approaches in the absence of reimbursement restrictions. Data were analyzed descriptively. Results LNAA experience was reported by 95% of clinicians. The most common indications were dietary non-compliance (100%) and adolescent/adult age (63%). LNAA therapy was typically initiated after age 15 (42%) or 18 years (32%). In current practice, most clinicians combine LNAA with a restricted natural protein diet (89%). In contrast, if reimbursement restrictions were removed, 89% reported that they would prefer combining LNAA with phenylalanine-free amino acid mixtures. Reported benefits included improvements in overall well-being (88%) and cognitive function (76%). LNAA discontinuation occurred in 24% of cases, mainly due to access difficulties, formulation intolerance, or adherence problems. Conclusions LNAA use in Turkey appears to be influenced by reimbursement constraints, with a marked discrepancy between current prescribing practices and clinicians’ preferred treatment strategies. These findings reflect clinician-reported preferences and perceived barriers and should not be interpreted as evidence of the clinical superiority of any specific LNAA regimen. Further comparative studies using patient-level outcomes are needed to determine the clinical implications of different LNAA treatment strategies.