Comparison of two different methods for measurement of phenylalanine in dried blood spots

• Published in: Clinical chemistry and laboratory medicine Vol. 38; no. 8; p. 773
• Main Authors: Rivero, A, Allué, J A, Grijalba, A, Palacios, M, Merlo, S G
• Format: Journal Article
• Language: English
• Published: Germany 01-08-2000
• Subjects: Amino Acid Oxidoreductases - metabolism; Humans; Neonatal Screening - methods; Phenylalanine - blood; Phenylalanine - metabolism; Phenylketonurias - blood; Phenylketonurias - diagnosis; Reagent Kits, Diagnostic; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 1434-6621
• DOI: 10.1515/CCLM.2000.110

Phenylketonuria is an inherited metabolic disorder caused by a defect in the hydroxylation of phenylalanine. Newborn screening is crucial for the diagnosis and treatment of this disease. A phenylalanine dehydrogenase-coupled enzymatic assay (Quantase) in microtiter plates for the screening of phenylketonuria was evaluated and compared with our routine method based on the modified fluorometric McCaman method. The test exhibited a linear calibration curve with a good slope as well as sufficient imprecision (< 10%), recovery (99.23+/-4.86%) and limit of detection (54.5 micromol/l). One hundred and ninety dried blood spots were analysed by this enzymatic method and compared with McCaman's. Although Quantase (Teknovas, Bilbao, Spain) showed a phenylalanine mean level in dried blood spot 18.2 micromol/l higher than that obtained with our routine method, the agreement between both techniques was considered acceptable.