Table 1.

Annual evolution of NTBC levels

Year	2016	2017	2018	2019
No. of patients with at least 1 NTBC measurement per year	47	63	63	60
No. patients with > 1 NTBC measurement per year	11	17	19	8
NTBC concentration in first sample of the year (µmol/L)	39	35.9	33.5	35.3
Median NTBC concentration (µmol/L)	39.5	34.3	37.9	34.6
No. of patients (%) with lower than recommended NTBC concentration in first annual determination	16 (34%)	24 (38.1%)	26 (41.3%)	19 (31.6%)
No. of patients (%) in which NTBC concentration normalized within the year	4/11 (36.3%)	5/17 (29.4%)	11/19 (57.9%)	2/8 (25%)

No number, NTBC nitisinone