Abstract
Since the enzymatic determination of P-hydroxylase activity remains limited to liver tissue, the diagnosis of most PKU homozygotes and especially heterozygotes relies on P-loading tests. In the present study, plasma was obtained before a P load (t=0) and a various time intervals after the load. The P and T concentrations in plasma were determined using a Beckman 6300 Amino Acid Analyzer. Twenty-five controls, 20 obligate heterozygotes and 10 patients with PKU were studied. The most informative parameters were obtained from values at t=0, 60 and 90 minutes. Age weight, the use of birth control, pills, values of P, T, P/T, P/T2, P/T3, the natural log of these parameters, and their various transformations were subjected to discriminant analysis with the statistical program BMDP7M. The various ratios for PKU homozygotes were 1-2 orders of magnitude higher than those of controls and heterozygotes. The analysis at t=0 (as suggested by some authors) revealed a 14.8% misclassification for heterozygotes. The best discrimination using 1 blood sample was at 60 minutes; only 1 of the controls was misclassified (3.7%). When females on birth control pills were excluded and using the variables of age, P/T at t=0 and 60 minutes, the function correctly classified all individuals. This procedure enabled the best discrimination between heterozygotes and controls thus far described.
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Bailey-Wilson, J., Blitzer, M., Kissling, G. et al. A TWO HOUR PHENYLALANINE (P) LOAD FOR CARRIER DETECTION OF PHENYLKETONURIA (PUK). Pediatr Res 18 (Suppl 4), 219 (1984). https://doi.org/10.1203/00006450-198404001-00757
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DOI: https://doi.org/10.1203/00006450-198404001-00757