[Did the change of technique of screening investigations influence on improvement of test credibility in recognizing and differentiating diagnostics of hiperphenylalaninemias?].

UNLABELLED

The phenylketonuria (PKU)/hyperphenylalaninemia (HPA) it is the most frequent inborn genetically conditioned error of metabolism of amino acids. It's occurrence in Polish population was estimated on the level 1:7.000 - 8.500. A. Folling was the first who described the phenylketonuria in 1934. It's diagnosed by neonatal screening, which was initiated in 1963 by prof. R. Guthrie.

MATERIAL

since 1985 till 2007 1,172,310 newborns investigated by the neonatal screening proceeding by the Laboratory of Screening and Inborn Errors of Metabolism in Cracow.

METHOD

in the years 1985-1998 the phenylalanine concentration in drop of blood on the blotting-paper was measured with half-quantitative Guthrie method. However after 1999 the colorimetric quantitative method measurement of phenylalanine concentration in capilar blood was introduced. It 2004 the cut-off value of phenylalanine in drop of blood on filter paper in neonatal screening investigation has was established below 3 mg/dl (till 2003 it was below 4mg/ dl). The blood had been taken from every newborn on filter paper Standard 903 between third and seventh day of the child's life. The verification of recognition in 1985-1988 was applied by Guthrie test, in 1989-2006 by the fluorymetric McCaman and Robins method, and since 2007 by colorimetric method.

RESULTS

in 1985-1998 the group of 137 newborns was distinguished due to the newborn screening (1:4.204), the classic PKU was recognized at 96 (1:5.999), however in next years (after change of method) due to screening 186 (1:4.788) newborns were distinguished, the classic PKU was recognized at 94 (1:5.236) newborn children. The lowering the point of cut-off influenced on frequency recognizing mild HPA, which grew up from 1:25.909 to 1:12.720. In 2001 we verified the recognition at 51 of 93 women (data were have gained over from archive of Outpatient Department), who where identified by the neonatal screening in 1985-1998, and in the face of observed phenylalanine values (<10 mg/dl - mild HPA) did not require dietetic treatment, and they gave up with medical care gradually. With regard on possibility pronouncement the signs of maternal PKU at their offspring, we ask 45 of them to contact with our Outpatient Clinic again, but only 36 with different reasons answered, at 28 of them the phenylalanine concentration was raised: 2-4 mg/dl - in 1 patient; 4-6 mg/ dl - in 6 patients; 6-10 mg/dl - in 11 patients; 10-20 mg/dl - in 12 patients. With this reason at 19 women the low-phenylalanine diet had to be introduce.

CONCLUSIONS

1. Applied Guthrie test limited the individual differentiating diagnostics of HPA, which led to relinquishment of medical observation, especially in girls and young women, the birth the child with maternal PKU could be the result of that. 2. Introduction of colorimetric method improved the detecting of the mild PKU and hyperphenylalaninemia considerably.