Symptoms and impact of aromatic l-amino acid decarboxylase (AADC) deficiency: a qualitative study and the development of a patient-centred conceptual model

Figures & data

Table 1. Caregiver characteristics (N = 14)^a.

Characteristic	Mean (SD)
Age (years)	43.9 (6.9)
Ethnic background (N = 8)^b	N (%)
White	7 (87.5)
Hispanic/Latino	1 (12.5)
Education
No formal qualifications	1 (7.1)
School	3 (21.4)
University degree or higher	10 (71.4)
Employment status
Employed full-time	1 (7.1)
Employed part-time	1 (7.1)
Self-employed	2 (14.3)
Full-time homemaker/caregiver	9 (64.3)
Other	1 (7.1)
Country
Italy	5 (35.7)
United States	7 (50.0)
Spain	1 (7.1)
Portugal	1 (7.1)
Relationship to individual with AADC deficiency
Mother	10 (71.4)
Father	2 (14.3)
Brother	1 (7.1)
Aunt	1 (7.1)

^aTwo participants were caregivers of the same individual.

^bParticipants in certain countries were not asked for their ethnicity as this was deemed as not being a standard procedure in these countries.

Table 2. Characteristics of individuals with AADC deficiency (N = 13).

Characteristic	Mean (SD)	Range
Age (years)
When first symptoms noticed (months)	11.9 (11.9)	0–48
At diagnosis with AADC deficiency (months)	30.1 (23.0)	7–96
Current (years)	6.9 (4.7)	1–15
Sex		N (%)
Male		9 (64.3)
Female		5 (35.7)
Uses a feeding tube		5 (35.7)
Uses a ventilator		4 (28.6)

Table 3. Data saturation matrix for symptoms, function and impacts.

	Participant number*
	201	202	203	301	204	205	601	401	602	603	604	605	606	607
Symptoms/function
Muscle and joint	P	S	S	S	S	P	S	S	S	S	P	S	S	S
Motor function	S	P	S	S	S	S	S	S	S	S	S	S	S	S
Fatigue	P	P		S		P	S	S	S	S	P	P	S	P
Sleep	P	P	P	S	P	P	S	S	S	S	P	S	S	P
Communication	S	P	S	S	S	P	P	P	P	S	P	P	P	P
Cognitive function	P	P	S	P	P	S	S	S	P	P	P	P	S	P
Gastrointestinal	P	P	P		P	P	S	S	P	S		S	P	S
Eating/feeding	S	P	S	S	S	S	S	S	S	S	S	S	S	S
Oculogyric crises		S	P	S	P	P		S	P		P	P	S	P
Seizures		S								S	S	S		P
Pain/discomfort		P	P	S	P		S	S	S	P	S	S	P	P
Impacts
Limitations with self-care	S	S	S	S	S	S		S	S	S	S	S	P	S
Ability to play	P	P	P	S	S	P	P	P	S	P	P	P	S	P
School/nursery	S	S	P	P	S	P	S	S	P	P	P	P	P	P
Limited interaction with peers	P	P	P	P		P	P	P	P	P	P	P	S	P
Frustration/ irritability	S	P	P	P	P		P	S	S	S	S	S	S	S
Upset/excessive crying	P			S		P	S	P			S	S		S

*Participant numbers are presented in the order the interviews were conducted. S = spontaneously reported symptoms/function/impacts, P = probed symptoms/function/impacts. Impacts were considered spontaneously reported unless explicitly probed. Highlighted cells indicate the first spontaneous report.

Figure 1. Conceptual model illustrating the relationships between symptoms and impacts of AADC deficiency. The conceptual model is designed to be read from the top, where there are the most proximal symptoms and functional impairments, to the bottom, where there are more distal impacts. The arrows show the relationships between the concepts, which are either unidirectional or bidirectional (for example, gastrointestinal symptoms impact eating and vice versa). Some relationships are between the larger external boxes, for example, all muscle and joint symptoms were reported to impact motor function. Other relationships are between the internal boxes, for example, muscle weakness and low muscle tone were reported to impact communication, but not cognitive function.