Journal of Inborn Errors of Metabolism and Screening (Aug 2018)

Metabolic Control in Patients With Phenylketonuria Pre- and Post-Sapropterin Loading Test

  • Catarina Sousa Barbosa BSc,
  • Manuela F. Almeida BSc,
  • Cátia Sousa BSc,
  • Sara Rocha MD,
  • Arlindo Guimas MD,
  • Rosa Ribeiro MD,
  • Esmeralda Martins MD, PhD,
  • Anabela Bandeira MD,
  • Bruno M. P. M. Oliveira PhD,
  • Nuno Borges PhD,
  • Anita MacDonald PhD,
  • Júlio C. Rocha PhD

DOI
https://doi.org/10.1177/2326409818788898
Journal volume & issue
Vol. 6

Abstract

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In Portugal, tetrahydrobiopterin (BH4)-responsive patients with phenylketonuria (PKU) are identified using a loading test (LT). Phenylalanine/natural protein (Phe/NP) intake is increased to elevate blood Phe prior to the LT. In a longitudinal retrospective study, the impact of Phe/NP titration post-LT in 58 patients (19.6 ± 8.2 years) with PKU during 4 study periods (SPs) was examined. In SP1 (2010-2013), patients were diet treated only; in SP2 (2014), the Phe/NP titration was followed by the LT in SP3 (2015). In SP4 (2016), patients received diet treatment only (n = 49) or BH4 + diet (n = 9). The median percentage blood Phe within the target range was higher in SP1 versus SP4 (64 [28-85] vs 45 [0-66]; P < .001). Our results suggest that transient Phe/NP titration, associated with a deliberate increase in NP, may adversely affect metabolic control. Controlled studies are necessary to examine the longer term impact of temporary increased NP with BH4 LT in non-BH4-responsive patients.