Development of an enzyme-mediated assay for phenylalanine in blood spots

We describe the optimization of a rapid procedure for the elution of phenylalanine from blood spots and the estimation of the amino acid eluted using an enzyme-mediated assay linked to a colorimetric detection system. The method is rapid, fully quantitative, interference-free, accurate and precise unlike many of the methods currently employed for phenylalanine determination. The performance of the proposed method may necessitate the review of reference ranges and cut-off assignment strategies.