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Table 1 Development and validation phases of the PKU-QOL questionnaire – disposition of subjects by phase and country

From: Development and psychometric validation of measures to assess the impact of phenylketonuria and its dietary treatment on patients’ and parents’ quality of life: the phenylketonuria – quality of life (PKU-QOL) questionnaires

  France Germany Italy Netherlands Spain Turkey UK Total
Exploratory interviews         
 Nutritionists 4 3 - - 4 - 6 17
 Pediatricians 3 4 - - 3 - 3 13
 Adolescents 13–17 years with PKU 4 4 - - 4 - 4 16
 Adults with PKU 4 4 - - 4 - 4 16
 Parents of children 4–12 years with PKU 4 4 - - 4 - 4 16
 Parents of adolescents 13–17 years with PKU 0 0 - - 3 - 0 3
Comprehension testing         
 Children 6–11 years with PKU 3 3 3 3 3 - 3 18
 Adolescents 12–17 years with PKU 4 4 4 4 4 - 4 24
 Adults with PKU 5 4 4 3 4 - 4 24
 Parents of children with PKU 5 5 5 5 5 - 6 31
Linguistic validation         
 Children 6–11 years with PKU - - - - - 3 - 3
 Adolescent 12–17 years with PKU - - - - - 3 - 3
 Adults with PKU - - - - - 3 - 3
 Parents of children with PKU - - - - - 3 - 3
Psychometric Validation study         
 Children 9–11 year with PKU 13 19 15 7 20 14 4 92
 Adolescents 12–17 years with PKU 10 20 26 10 20 20 4 110
 Adults with PKU 18 21 22 7 21 8 7 104
 Parents of children ≤8 years with PKU 10 8 8 6 8 6 6 52
 Parents of children 9–11 years with PKU 13 19 15 7 20 4 14 92
 Parents of adolescents with PKU 10 19 26 10 20 4 20 109