[Evaluation of 6-years' experience of screening for hyperphenylalaninemia caused by cofactor deficiency].

Since the treatment of tetrahydrobiopterin deficiency differs from that for phenylalanine-hydrolase deficient patients, early differential diagnosis of the various types of hyperphenylalaninemia is essential. Results of screening for tetrahydrobiopterin deficiency in 261 cases with hyperphenylalaninemia, including 152 newborns, are reported. Urinary pteridine analysis appears as a valuable method for the recognition of cofactor deficiency. However, accurate interpretation depends on the quality of urine sampling (especially for DHRP deficiency recognition), age-paired comparison and possible pathological interferences.