Using the fluorescence spot test for neonatal screening of G6PD deficiency.

To establish the neonatal screening method of glucose-6 phosphate dehydrogenase (G6PD) deficiency, G6PD activity was measured using the fluorescence spot test (FST) using dried blood samples on filter paper. The G6PD/6PGD rate test of venous blood samples was further performed for confirmation. The positive G6PD deficiency rate was 4.2% and its detection rates were 3.7% for all neonates and 5.2% only for male newborns when FST was used for neonatal screening. Conformation rates by use of G6PD/ 6PGD ratio test for G6PD deficiency were 86.8% and 100% particularly in the severely deficient groups. Both sensitivity and specificity were very high in the severely deficient groups. FST can be used in neonatal screening of G6PD deficiency because of its high accuracy, applicability, and simplicity. Moreover, a high volume of dried blood samples on filter paper can be tested quickly. It is very favorable to diagnose and treat G6PD deficiency early in high incidence districts.

A survey for the incidence of phenylketonuria in Guangdong, China.

A multicenter cooperative investigated the incidence of Phenylketonuria (PKU) in the central, southern and western areas of Guangdong province and its surrounding districts. Tests to measure phenylalanine (Phe) on dried blood spots on filter paper cards used BIA and thefluorescence assay. Four hundred sixty-one thousand eight hundred five (461,805) newborns were screened and 14 cases of persistent hyperphenylalaninemia (PHPA) were detected. The incidence of PHPA was 1/33,000, including 1/77,000 for classical PKU; 1 in 66,000 for hyperphenylalaninemia (HPA) and 1 in 461,805 for BH4 deficiency. A high variation in PKU incidence in the different districts was observed. The differences may be attributed to the variations in gene frequency of PKU in the different districts and to bioethical consideration especially as regards reproduction in different areas.

Screening for tetrahydrobiopterin deficiency among hyperphenylalaninemia patients in Southern China.

OBJECTIVES: To assess the incidence of tetrahydrobiopterin (BH4) deficiency among patients with hyperphenylalaninemia (HPA) in southern Chinese and evaluate clinical outcome and gene mutations in tetrahydrobiopterin deficient patients. METHODS: Urinary neopterin (N) and biopterin (B) was analyzed in 87 patients with hyperphenylalaninemia by high-performance liquid chromatography. Further combined loading tests with phenylalanine (Phe) (100 mg/kg) and tetrahydrobiopterin (BH4) (7.5 mg/kg) were performed in suspected patients with abnormal urinary pterin profiles. Gene mutation analysis was performed for patients with BH4 deficiency and their parents. BH4 deficient patients were treated with BH4 and neurotransmitter precursors after diagnosis. Blood phenylalanine levels, clinical symptoms and mental development were followed up. RESULTS: Eleven patients were diagnosed as having BH4 deficiency caused by 6-pyruvoyl tetrahydropterin synthase (PTPS) deficiency. The incidence of tetrahydrobiopterin (BH4) deficiency among patients with hyperphenylalaninemia (HPA) in southern Chinese was 10%. Combined loading tests with phenylalanine and oral BH4 were done in 4 of 11 patients and their phenylalanine levels were decreased to normal 4 - 6h after BH4 administration. Four different mutations (P87S, N52S, D96N and G144R) in the PTPS gene were detected in 5 families. Five PTPS-deficient patients were treated with synthetic BH4, neurotransmitter precursors (L-dopa plus carbidopa, and 5-hydroxytryptophan). They had satisfactory physical and mental development after treatment. One patient with partial PTPS deficiency had normal growth and mental development without treatment. CONCLUSIONS: Our results emphasize that screening for BH4 deficiency should be carried out in all patients with hyperphenylalaninemia in order to minimize the misdiagnosis. Patients with BH4 deficiency should be treated early with BH4 and a combination of neurotransmitter precursors.