Fig. 4.

Blood Phe target ranges (μmol/L) and frequency of blood Phe monitoring for different patient groups. a Box and whisker plot of blood Phe target ranges per patient group: boxes represent interquartile range (thick line indicating the median, with value indicated in the plot), and dashed whiskers minimum and maximum values. b Frequency histogram of blood Phe monitoring frequency. ‘Other’ was as follows: newborns and infants: ‘sometimes weekly, sometimes 2-weekly’; young children: ‘1–2 years: 2-weekly; 2–3 years: 3-weekly; 3–4 years: monthly’; older children: not specified; adolescents: ‘2-weekly or monthly’ ‘depends on patient collaboration’; not specified; adults: ‘It depends on the patient collaboration’, not specified; maternal PKU: ‘sometimes weekly, sometimes 2X per week’; not specified (2). ‘n’ represents the number of questionnaires which provided an answer for each group. Age groups were as follows: newborns and infants, <1 year of age; young children, 1–4 years of age; older children, 5–10 years of age; adolescents, 11–17 years of age; adults, ≥18 years of age