Long-term follow-up of patients with phenylketonuria treated with tetrahydrobiopterin: a seven years experience

Table 4 Predictors of BH4-responsiveness

	BH4 responders (N = 19)	BH4 non-responders (N = 24)	p-value
Gender	11 M/8 F	9 M/15 F	0.18
Age (years) at BH4 loading test (Mean ± SD)	14.4 ± 4.5	13.6 ± 4.8	0.63
Phe^§ at diagnosis (Mean ± SD)	1148 ± 613	1612 ± 816	0.04
Phe tolerance* [Mean (range)]	549 (235-1920)	335 (220-630)	0.02
Genotype One allele with PRA > 1%	17	14	0.02
Two alleles with PRA > 1%	13	5	0.001
Phe^§ at loading test (T0) (Mean ± SD)	615 ± 180	695 ± 228	0.2
Tyr^§ at loading test (T0) (Mean ± SD)	52.35 ± 8.5	48.12 ± 12.4	0.36
Phe/Tyr at loading test (T0)	12.58 ± 4.5	16.9 ± 5.1	0.01

*Phe tolerance (mg/day), as calculated at 5 years of age. ^§ Phe and Tyr plasma concentrations are expressed in micromol/L. PRA: predicted residual activity.

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