Transition of young adults with phenylketonuria from pediatric to adult care.

BACKGROUND: Transition from pediatric to adult health care is a particularly vulnerable period for patients with inborn metabolic diseases. Aim of the present study was to evaluate the current transition situation of patients with phenylketonuria (PKU) in Leipzig, Germany, by analysis of the medical care, metabolic control, patients' satisfaction, socio-economic and psychosocial status, in order to identify areas of weakness and potential improvement. METHODS: Patients who had been transferred from pediatric to adult medical care between 2005 and 2008 were identified. An interview was performed using a questionnaire. Pediatric case notes and the present physician's case notes were analyzed retrospectively. Socio-demographic data were compared to data derived from the annual statistics of the city of Leipzig, Germany in 2008. RESULTS: seventy two transferred patients were identified and included in the study, 48 patients responded to the questionnaire, the data of 24 non-responders were analysed retrospectively. About 90% of the responding patients with PKU were satisfied with the current transition situation. However, they agreed to several suggestions of improvement. Most specifically an interdisciplinary appointment before the definite transfer to the adult clinics was asked for. At the time of transition, most of the patients were in good metabolic control according to current treatment guidelines (median dried blood phenylalanine concentration 853 µmol/l before versus 690 µmol/l after transition). Of the interviewed patients 92% were still on a low phenylalanine diet in combination with the intake of a phenylalanine free amino acid mixture. Of the interviewees 77% carried a secondary school certificate or a secondary modern school qualification, but only 19% had achieved senior high school diploma (controls 38.2%). Marital status was comparable with the population of Leipzig. However, fewer patients with PKU had children (15% versus 37%). CONCLUSION: Transition of patients with PKU from pediatric to adult care seems to be successful in Leipzig. Patients were mostly satisfied with the transition situation. Still, some suggestions for improvements appeared to be desirable. During transition medical care and metabolic control were stable. However, with regard to psychosocial and socioeconomic data differences to the control population were detected.

Validation of the phenylalanine/tyrosine ratio determined by tandem mass spectrometry: sensitive newborn screening for phenylketonuria.

The efficacy of the tandem mass spectrometry as a tool for the newborn screening of phenylketonuria, an inherited metabolic disorder, was investigated. Precision, reproducibility, selectivity and sensitivity were validated for phenylalanine and tyrosine measurements from dried blood spots. Bland-Altman plots were used to assess the agreement with conventional methods like fluorometry and ion exchange chromatography. The utility of the phenylalanine/tyrosine ratio for discrimination between mild hyperphenylalaninemia and classical types of phenylketonuria was investigated. Depending on concentration levels of phenylalanine and tyrosine the within-run and between-run assay variability ranged between 4.2% and 12.7%. Higher recoveries and a lower detection limit were found for the mass spectrometric method when compared to the fluorometric method. Pearson correlation coefficients of 0.91 for tandem mass spectrometry vs. fluorometric method, as well as 0.95 for tandem mass spectrometry vs. ion exchange chromatography were calculated. The closest agreement between methods was observed between tandem mass spectrometry and ion exchange chromatography. The results demonstrate a high efficacy of the tandem mass spectrometric method for quantitative determination of phenylalanine and tyrosine from dried blood spots. The phenylalanine/tyrosine ratio is crucial to improve the specificity and positive predictive value for the diagnosis of classical phenylketonuria.