Phenylketonuria

Blood phenylalanine (phe) levels should be obtained at periodic intervals to monitor the efficacy of therapy in patients with PKU. The recommended interval is:

• Weekly for infants <1 year of age, whose nutritional requirements change frequently as a result of rapid growth

• Every 2 weeks from 1 to 12 years of age

• Monthly after 12 years of age

• Twice weekly during pregnancy.[1]National Institutes of Health Consensus Development Panel. National Institutes of Health consensus development conference statement: phenylketonuria - screening and management. 2000 [internet publication]. http://consensus.nih.gov/2000/2000Phenylketonuria113html.htm

Most metabolic specialists agree that the desired therapeutic range for blood phe is 2 to 6 mg/dL. Levels above or below the therapeutic range should prompt an adjustment in therapy.

A diet diary should be submitted with each blood sample so that the adequacy of the diet can be assessed and adjustments can be made when blood phe levels are not within range. Patients should be seen for follow-up at regular intervals, with assessments of growth and development. Neuropsychological testing should be obtained if screening suggests a cognitive or behavioral problem. Once patients reach adolescence, a bone density scan should be obtained. Vitamin D levels should be monitored over time. If osteopenia is identified, serum calcium, phosphorus, and parathyroid hormone levels should also be obtained. Vitamin D should be supplemented in any patient with a documented vitamin D deficiency.