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Table 7 Reliability coefficients of the Child, Adolescent and Adult PKU-QOL questionnaires at baseline

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

  Child PKU-QOL (n = 92) Adolescent PKU-QOL (n = 110) Adult PKU-QOL (n = 104)
  Cronbach α ICC Cronbach α ICC Cronbach α ICC
Self-rated health status - - - 0.49 - 0.67
Headaches - 0.37 - 0.52 - 0.59
Stomach aches - 0.33 - 0.34 - 0.61
Tiredness - 0.27 - 0.51 - 0.62
Irritability/Anger - 0.45 - 0.53 - 0.42
Aggressiveness - 0.44 - 0.64 - 0.53
Moodiness - 0.47 - 0.59 - 0.66
Sadness - 0.35 - 0.52 - 0.57
Anxiety - 0.44 - 0.70 - 0.60
Lack of concentration - 0.47 - 0.60 - 0.69
Slow thinking - 0.55 - 0.61 - 0.63
Trembling hands - - - - - 0.75
Emotional impact of PKU 0.37 0.60 0.70 0.83 0.71 0.84
Practical impact of PKU 0.43 0.45 0.47 0.75 0.50 0.70
Social impact of PKU 0.59 0.70 0.45 0.83 0.63 0.77
Overall impact of PKU 0.69 0.67 0.80 0.88 0.79 0.84
Anxiety – blood test 0.26 0.64 0.61 0.95 0.77 0.87
Anxiety – blood Phe levels - 0.64 - 0.76 - 0.63
Anxiety – blood Phe levels during pregnancy - - - - - 0.71
Financial impact of PKU - - - - - 0.65
Information on PKU - - - - - 0.60
Adherence to Phe-free protein supplements 0.46 0.48 0.70 0.64 0.67 0.84
Practical impact of Phe-free protein supplements - 0.29 0.82 0.87 0.67 0.67
Guilt if poor adherence to Phe-free protein supplements - 0.60 - 0.59 - 0.67
Relationships within family because of Phe-free protein supplements - 0.72 - 0.69 - 0.57
Taste – Phe-free protein supplements - 0.81 - 0.88 - 0.76
Food temptations 0.63 0.55 0.77 0.74 0.78 0.68
Adherence to dietary protein restriction 0.25 0.43 0.59 0.80 0.81 0.77
Social impact of dietary protein restriction 0.74 0.58 0.88 0.86 0.77 0.83
Practical impact of dietary protein restriction - - 0.74 0.71 0.78 0.70
Overall impact of dietary protein restriction - - 0.74 0.80 0.88 0.79
Taste – specialty low-protein food - 0.47 - 0.57 - 0.73
Food enjoyment - 0.21 - 0.31 - 0.77
Guilt if dietary protein restriction not followed - 0.60 - 0.61 - 0.74
Overall difficulty following dietary protein restriction - 0.55 - 0.59 - 0.54
  1. ICC: Intraclass Correlation Coefficient; Phe: phenylalanine; PKU: phenylketonuria; QOL: quality of life. Reliability coefficients ≥0.70 are set in bold type.