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Plasma phenylalanine and tyrosine levels revisited in heterozygotes for hyperphenylalaninaemia

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Summary

We examined the value of the fasting plasma phenylalanine/tyrosine ratio obtained in an ordinary clinical setting for assessing the probability of being a heterozygote for hyperphenylalaninaemia. This biochemical test was found to be of little value in those with a high (66%) prior risk of heterozygosity, because it could not reduce the risk below 12%. However, in a population with a prior risk of only 2%, it discriminates the 3% with a 19% risk from the 97% with a risk of 1.5% or less. This simple method could usefully be applied to such a population, in order to select those at higher risk for further investigation using molecular genetics.

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Correspondence to J. M. Saraiva.

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Saraiva, J.M., Seakins, J.W.T. & Smith, I. Plasma phenylalanine and tyrosine levels revisited in heterozygotes for hyperphenylalaninaemia. J Inherit Metab Dis 16, 105–109 (1993). https://doi.org/10.1007/BF00711323

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Keywords

  • Public Health
  • High Risk
  • Internal Medicine
  • Tyrosine
  • Clinical Setting