Table 3.

Final scaling/scoring structure of the four PKU-QOL questionnaires

Modules	Domain scores	PKU-QOL items (for multi-item scores)	Child PKU-QOL (40 items)	Adolescent PKU-QOL (58 items)	Adult PKU-QOL (65 items)	Parent PKU-QOL (54 items)
PKU symptoms	Self-health rated status			√	√	√
	Headaches		√	√	√	√
	Stomach aches		√	√	√	√
	Tiredness		√	√	√	√
	Lack of concentration		√	√	√	√
	Slow thinking		√	√	√	√
	Trembling hands				√
	Irritability		√	√	√	√
	Aggressiveness		√	√	√	√
	Moodiness		√	√	√	√
	Sadness		√	√	√	√
	Anxiety		√	√	√	√
PKU in general	Emotional impact of PKU	Unfairness having PKU	√	√	√	√
		Worries about the future		√	√	√
		Worries about future children		√	√	√
		Disease acceptance	√	√	√	√
		Self-esteem	√	√	√	√
	Practical impact of PKU	Burden of care for PKU	√	√	√	√
		Burden of physician visits	√	√	√	√
		Maintaining activity at work		√	√	√
		Time in administrative tasks			√	√
		Missing work				√
		Difficulty to do other things due to the burden of care for PKU				√
	Social impact of PKU	Explain situation to others	√	√	√	√
		Discussing PKU within family	√	√	√	√
		Difficulty making friends	√	√	√	√
		Impact on relationship with partner			√	√
		Maintaining friendship				√
		Impact of PKU on child’s siblings				√
	Overall impact of PKU*	Items from Emotional, practical and social impact of PKU	√	√	√	√
	Anxiety – blood tests	Anxiety having blood test in the arm	√	√	√	√
		Anxiety having blood test in the finger	√	√	√	√
	Impact of child anxiety – blood tests	Impact of child anxiety of blood test in the arm on parent				√
		Impact of child anxiety of blood test in the finger on parent				√
	Anxiety – Phe levels		√	√	√	√
	Anxiety – Phe levels during pregnancy				√
	Financial impact of PKU				√	√
	Information on PKU				√	√
Administration of Phe-free protein supplements	Adherence to Phe-free protein supplements	Frequency of supplement intake	√	√	√
		Adherence/compliance to supplement	√	√	√	√
		Missing supplements because of school		√
		Missing supplements because of work constraints		√	√
	Guilt if poor adherence to Phe-free protein supplements		√	√	√	√
	Impact of Phe-free protein supplements on family		√	√	√	√
	Practical impact of Phe-free protein supplements	Embarrassment/shame taking supplements	√	√	√
		Lack of spontaneity/freedom due to supplements		√	√	√
		Difficulty eating out due to supplements		√	√	√
		Difficulty travelling, transporting supplements for special event situations		√	√	√
	Taste - Phe-free protein supplements		√	√	√
	Management of Phe-free protein supplements					√
Dietary protein restriction	Food temptations	Temptation/adherence	√	√	√
		Temptation not emotionally	√	√	√
	Adherence to diet	Adherence/compliance to the diet	√	√	√	√
		Eat forbidden things secretly	√	√	√
		Change in diet because of school/college/university constraints		√	√
		Change in diet because of work constraints		√	√
		Eat forbidden food intentionally
	Management of diet	Difficulty monitoring dietary protein restriction				√
		Difficulty monitoring the amount of calories				√
		Sadness to forbid food to child				√
		Worry that child eats things secretly				√
		Hard when child has to follow diet in front of others				√
		Impact of diet on relationship with child				√
	Practical impact of diet	Burden of weighing/estimating quantity of protein in food		√	√	√
		Lack of spontaneity/freedom due to PKU diet		√	√	√
		Difficulty eating out due to PKU diet		√	√	√
		Need to plan meals in advance		√	√	√
		Time-consuming aspects of the diet		√	√	√
		Complexity cooking		√	√	√
		Difficulty travelling, transporting PKU food for special event situations		√	√	√
	Social impact of diet	Feeling different because of diet	√	√	√
		Relationship within family	√	√	√
		Temptation emotionally	√	√	√
		Embarrassment/shame following diet	√	√	√
		Isolation because of diet	√	√	√
		Cooking for others			√
	Overall impact of diet*	Items from practical and social impact of dietary protein restriction		√	√
	Overall difficulty following diet		√	√	√
	Guilt if diet not followed		√	√	√	√
	Taste of low-protein food		√	√	√
	Food enjoyment		√	√	√	√

In bold*: Overall multi-item scores including items from different domains.

Phe: phenylalanine; PKU: phenylketonuria.