Urinary pterin analysis in screening of tetrahydrobiopterin def iciency

Objective To screen out the tetrahydrobiopterin def iciency in patients with hyperphenylalaninemia by urinary pterin analysis. Methods Analysis of urinary neopterin (N) and biopterin (B) was done in 96 patients with hyperphenylalaninemia by high performance liquid chromatography. Combined BH4 loading test was performed for patients with abnormal urinary pterin profiles. Results Eleven patients were diagnosed as ha ving BH4 deficiency caused by 6 pyruvoyl tetrahydrobiopterin synthase deficiency. They had a much high N/B ratio(N/B:197±250) and a very low B percentage (1.0±0.8)%. Blood phenylalanine levels were decreased from (720 1 200) μmol/L to (120 240) μmol/L after taking BH4 tablets in 4 of 11 patients. Conclusion The incidence of BH4 deficiency among hyperphenylalaninemia is about 12%. Analysis of urinary pterin is feasible and effective in screening of BH4 deficiency.