Comparison of two different methods for measurement of phenylalanine in dried blood spots.
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.
Rivero
A
A
Clinical Chemistry Service, Hospital de Navarra, Pamplona, Spain. sgarciam@cfnavarra.es
Allué
J A
JA
Grijalba
A
A
Palacios
M
M
Merlo
S G
SG
D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D006801:Humans; D015997:Neonatal Screening / Q000379:methods*; D010649:Phenylalanine / Q000097:blood* / Q000378:metabolism; D010661:Phenylketonurias / Q000097:blood* / Q000175:diagnosis*; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D011933:Reagent Kits, Diagnostic; D010649:Phenylalanine; D000594:Amino Acid Oxidoreductases; C022342:phenylalanine oxidase