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Comparative diagnostic value of phenyla‐lanine challenge and phenylalanine hydroxylase activity in phenylketonuria
Author(s) -
Hsieh Monica C.,
Berry Helen K.,
Bofinger Mary K.,
Phillips Pamela J.,
Guilfoile Mary Beth,
Hunt Melanie M.
Publication year - 1983
Publication title -
clinical genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 102
eISSN - 1399-0004
pISSN - 0009-9163
DOI - 10.1111/j.1399-0004.1983.tb01975.x
Subject(s) - phenylalanine , phenylalanine hydroxylase , metabolite , chemistry , medicine , endocrinology , phenylketonurias , excretion , urinary system , amino acid , biochemistry
Serum phenylalanine (phe) concentrations during and following phe challenges and liver phenylalanine hydroxylase (PH) activity were compared in 13 phenylketonuric (PKU) patients. These patients were separated into two groups: eight patients with no detectable PH activity (PH°) and five patients with residual PH activity (PH ‐ ) ranging from 9 to 24% of the activity obtained in 10 non‐PKU subjects. The rise in serum phe concentration during 3 days of oral loading did not differentiate the two groups. However, the difference in serum phe concentration of the PH° and PH ‐ groups reached statistical significance at 24 h postloading (p<0.01). We concluded that combined results from multiple measurements during the oral challenge, namely serum phe concentration after termination of loading, serum phe clearance rate, post‐loading phe tolerance index and urinary metabolite excretion, make a better indicator for predicting residual PH activity for the majority of PKU subjects than peak phe concentrations during phe challenge.