The Impact on Quality of Life of Diet Restrictions and Disease Symptoms Associated with Adult Phenylketonuria (PKU) in Sweden


Hoxer C1, Gralén K2, Olofsson S2, Persson U2, Quinn J1, Okhuoya P1
1Biomarin Europe Ltd, London, UK, 2The Swedish Institute for Health Economics, LUND, Sweden


Quality of life (QoL) of patients with phenylketonuria (PKU) is impacted by both symptoms and requisite dietary restrictions. Our objective was to estimate the impact of PKU symptoms and dietary restrictions on QoL to better understand the value of treatments and their potential to reduce disease burden.


A web-based survey of adults in the Swedish general population, PKU patients and their carers was performed using Time Trade Off (TTO) and Discrete Choice Experiment (DCE) methods to elicit health utility and preference information regarding PKU health states. Vignettes were developed with clinical experts for different PKU health states considering symptom severity (cognitive, emotional, and physical) and/or dietary restrictions Data was collected using TTO questionnaires for diet (n=500) and for symptoms (n=500), and one DCE questionnaire (n=1,117).


The total disutilities associated with emotional, cognitive and physical symptoms at mild, moderate, or severe severity levels respectively, was 0.064, 0.154, 0.487 in the TTO and 0.122, 0.437, 1.522 in the DCE. Cognitive symptoms provided the most disutility for mild disease as did physical symptoms for severe disease. The disutility of a partly restricted diet without medical food (MF), a partly restricted diet with MF, and a restricted diet with MF, respectively, was 0.061, 0.119, 0.177 in the TTO and 0.043, 0.031, 0.108 in the DCE.


Data was collected using the general population, PKU patients and carers which also highlighted the disability paradox in mild disease. The differences between TTO and DCE estimates are consistent with previous studies. Both methods showed that disease severity and diet restrictions, as highlighted by the preferences of the general public have significant impact on QoL.

Conference/Value in Health Info

2020-11, ISPOR Europe 2020, Milan, Italy

Value in Health, Volume 23, Issue S2 (December 2020)




Methodological & Statistical Research, Patient-Centered Research

Topic Subcategory

Health State Utilities, Patient-reported Outcomes & Quality of Life Outcomes, Stated Preference & Patient Satisfaction, Survey Methods


Rare and Orphan Diseases

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