Sensitivity of electrospray-tandem mass spectrometry using the phenylalanine/tyrosine-ratio for differential diagnosis of hyperphenylalaninemia in neonates.
The sensitivity of amino acid analysis by electrospray-tandem mass spectrometry (ESI-TMS) in differential diagnosis of the different forms of hyperphenylalaniemias (HPA) was studied in a total number of 78 dried blood samples from neonates with increased phenylalanine (Phe) concentrations (> 150 micromol/l). Simultaneous quantitative analysis of Phe and tyrosine (Tyr) were performed by ESI-TMS. By means of the Phe/Tyr-ratio it was possible to differentiate between phenylketonuria (PKU; n = 23) and nonPKU-HPA patients (n = 35; P < 0.001) with a sensitivity of 100%. Neonates with transient HPA (n = 9) showed a lower Phe/Tyr-ratio compared to the nonPKU-HPA patients (P < 0.001). Amino acid analysis by ESI-TMS represents a powerful diagnostic tool in differential diagnosis of HPA and is an appropriate technique in the setting of neonatal screening based on dried blood spots.
Division of Metabolic Diseases, University Children's Hospital, Heidelberg, Germany.
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A
Schulze
D
D
Kohlmueller
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E
Mayatepek
D003937:Diagnosis, Differential; D006801:Humans; D007231:Infant, Newborn; D013058:Mass Spectrometry / Q000379:methods*; D010649:Phenylalanine / Q000097:blood*; D010661:Phenylketonurias / Q000097:blood / Q000175:diagnosis*; D011237:Predictive Value of Tests; D012016:Reference Values; D012680:Sensitivity and Specificity; D014443:Tyrosine / Q000097:blood*
D014443:Tyrosine; D010649:Phenylalanine