Phenylketonuria (PKU) is a rare genetic disease that requires lifelong treatment, including specialized foods and dietary formulas. PKU patients must keep their blood phenylalanine (Phe) levels within normal range. If they don’t, they can develop skin rashes, seizures, hyperactivity, and intellectual disabilities. And if a woman with PKU does not follow a special diet while pregnant, she may develop a condition called maternal PKU, which can cause miscarriage or harm to a developing fetus. All PKU patients must monitor their Phe levels throughout their lives.
But PKU management—particularly targeted blood Phe ranges—differs among clinics. The American College of Medical Genetics (ACMG) published a management guideline in 2014, updating the National Institutes of Health consensus statement published in 2000. The ACMG guideline recommends that all individuals with PKU maintain blood Phe levels between 120-360 µMol/L.
At the ACMG Annual Clinical Genetics Meeting held in Tampa, Florida, March 8-12, 2016, Elaina Jurecki, RD, along with co-authors, presented a study designed to examine current PKU management practices in clinics across the United States and to determine adherence rates to the ACMG and clinic guidelines.
A team of physicians and dietitians developed a questionnaire to assess US metabolic clinics’ treatment guidelines and patient adherence to these guidelines. The study’s primary objectives were to assess patient adherence to the blood Phe targets and clinic adherence to the ACMG recommendations.
The questionnaire was distributed to 130 clinics that had 20 or more PKU patients. Only 1 questionnaire was completed per clinic.
The response rate was 38%, with 44 out of 130 clinics completing the questionnaire. Respondent clinics reported on a total of 3772 PKU patients, representing approximately half of the patient population being followed in US metabolic clinics. On average, the clinics were actively following 68% of their PKU patient population. The remaining patients were reported to be inactive, as these individuals had not been seen in the past 3 years. Approximately 40% of patients were infants and children, 20% adolescents, and 40% adults, with 2% who were pregnant or planning to become pregnant.
The mean lower and upper targeted blood Phe ranges for children and adolescents used in the clinics were reported to be consistent with the ACMG guidelines of 120-360 µMol/L. For adults, the targeted ranges in the clinics were slightly higher than ACMG guidelines, with a mean upper limit of 445 µMol/L. Only 31% of those aged 18-29 years and 22% of those aged ≥30 years were reported with blood Phe levels consistent with the ACMG guidelines.
The mean range recommended for pregnant women was 115-300 µMol/L. A higher percentage of infants and children (83% of those aged 0-4 years and 68% of those aged 5-12 years) had mean blood Phe levels within the clinic’s targeted range, as compared with adolescents (46% of those aged 13-17 years) and adults (36% of those aged 18-29 years, and 27% of those aged ≥30 years), except for women who were pregnant or planning to become pregnant (71%).
Eighty-nine percent of clinics had recommendations on frequency of blood Phe testing, with more frequent testing recommended for infants (aged <1 year, 49 tests per year) and children (aged 1-12 years, 20-26 tests per year) than adolescents (aged 13-17 years, 18 tests per year) and adults (aged ≥18 years, 15 tests per year).
This survey only represents approximately half of the PKU patient population actively followed in clinic. From the survey, authors found that the clinics’ targeted blood Phe range for infants and children was consistent with that of the ACMG guideline, although less than a third of clinics complied with these guidelines for adults. The percentage of patients achieving their target blood Phe levels progressively decreased with age, which, according to the authors, suggests compromised metabolic control with increasing age.
A better monitored Phe level can help stave off symptoms of PKU but can be a challenge, as the clinic inconsistency demonstrates. With more consistency, the authors argue, PKU patients can see improved neurocognitive and psychological outcomes.
Jurecki E, Cederbaum S, Kopesky J, et al. National Study to Assess Current Practices of the Management of Phenylketonuria. Poster presented at: American College of Medical Genetics Annual Clinical Genetics Meeting; March 9-11, 2016; Tampa, FL. Abstract 186. https://acmg.expoplanner.com/index.cfm?do=expomap.sess&event_id=7&session_id=1122