Mass screening of urea cycle diseases: a new mass screening method of hyperornithinemia by using two coupling enzymes.

We devised a new microfluorometric mass screening method for determining ornithine in only one blood disc of 3 mm in diameter (blood of 2-3 microliters) by use of two coupling enzymes, ornithine aminotransferase and delta'-pyrroline-5-carboxylate reductase. We could apply this method to some cases of gyrate atrophy of the choroid and retina. Our method can be applied in range of 0 to 12-16 nmoles or about 54.8 mg% or about 4 mM ornithine in blood. Ornithine values by our method were well correlated with those by an amino acid analyser.