López-Laso Eduardo, Ormazabal Aida, Camino Rafael, Gascón Francisco J, Ochoa Juan J, Mateos María E, Muñoz María J, Pérez-Navero Juan L, Lao José I, Vilaseca María A, Artuch Rafael
Department of Paediatrics, Hospital Universitario Reina Sofía, Córdoba, Spain.
Clin Biochem. 2006 Sep;39(9):893-7. doi: 10.1016/j.clinbiochem.2006.03.002. Epub 2006 Apr 19.
To evaluate the usefulness of Phe loading test in patients for the diagnosis of guanosine triphosphate cyclohydrolase 1 deficiency (GTPCH).
We studied one family composed of 13 members harbouring the Q89X mutation in the GTPCH gene, a non-related pediatric patient with GTPCH deficiency and 8 pediatric controls. 100 mg/kg of L-phenylalanine was orally administered, and blood spot samples were taken at baselines 1, 2, 4 and 6 h post-load.
Two out of 7 pediatric patients showed a phenylalanine/tyrosine ratio higher than the previously reported cut-off value of 5.25 at 4 h, while 6 of the 7 adult patients showed a higher value. The only adult patient with a phenylalanine/tyrosine ratio below 5.25 at 4 h was asymptomatic.
A cut-off value of 5.25 seems reliable for interpreting Phe loading test in adult patients with GTPCH deficiency, although a lower value should be established for pediatric patients.
评估苯丙氨酸负荷试验在诊断鸟苷三磷酸环化水解酶1缺乏症（GTPCH）患者中的实用性。
我们研究了一个由13名携带GTPCH基因Q89X突变的成员组成的家系、一名患有GTPCH缺乏症的非相关儿科患者以及8名儿科对照。口服给予100mg/kg的L-苯丙氨酸，并在负荷后1、2、4和6小时的基线时间采集血斑样本。
7名儿科患者中有2名在4小时时苯丙氨酸/酪氨酸比值高于先前报道的5.25的临界值，而7名成年患者中有6名比值更高。4小时时苯丙氨酸/酪氨酸比值低于5.25的唯一成年患者无症状。
对于GTPCH缺乏症成年患者，5.25的临界值似乎可可靠地用于解释苯丙氨酸负荷试验，不过对于儿科患者应确定更低的临界值。
