Does a single plasma phenylalanine predict quality of control in phenylketonuria?

• Published in: Archives of disease in childhood 1998-02, Vol.78 (2), p.122-126
• Main Authors: MacDonald, A, Rylance, G W, Asplin, D, Hall, S K, Booth, I W
• Format: Article
• Language: English
• Subjects: Adolescent; Age; Aminoacid disorders; Biological and medical sciences; Biomarkers - blood; Blood; Child; Child, Preschool; Children; Correlation; Dietary Proteins - administration & dosage; Energy Intake; Errors of metabolism; Female; Food; Hospitals; Humans; Infant; Male; Medical sciences; Metabolic diseases; Original; Parents; Parents & parenting; Patients; phenylalanine; Phenylalanine - blood; phenylketonuria; Phenylketonurias - blood; Phenylketonurias - therapy; plasma phenylalanine; Predictive Value of Tests; Proteins; Statistical Analysis; Working groups
• ISSN: 0003-9888; 1468-2044
• DOI: 10.1136/adc.78.2.122

A 1993 MRC working group on phenylketonuria suggested standardising blood phenylalanine measurements by taking blood samples at the same time each day. Since it is not known how representative of a 24 hour period a single phenylalanine concentration is, the aim of this study was to investigate the 24 hour variability of plasma phenylalanine in well controlled children with phenylketonuria. Sixteen subjects, 12 girls and four boys aged 1 to 18 years, had hourly venous blood samples collected for 13 hours between 09.00 and 21.00 on one day. Serial skin puncture blood specimens were then collected at 24.00, 03.00, and 06.00 within the same 24 hour period. All food and drink was weighed. The median variation in plasma phenylalanine concentration was 155 μmol/l/day, with a minimum of 80 and a maximum of 280. The highest concentration occurred in the morning between 6.00 and 9.00 in 63% of subjects; the lowest occurred between midday and midnight in 94%. Concentrations