To maintain good metabolic control and ensure optimal growth, frequent adjustments of the diet are necessary.

Monitoring should include the following markers:

Monitoring dietary management and outcome of PKU

Monitoring of nutritional status and suggested frequency1
Lab monitoring	Disease specific monitoring: blood PHE and TYR concentrations
Nutritional monitoring of the diet: Dietary intake; food records	Each clinic visit
Anthropometrics:Growth (weight, length/height, BMI) Waist circumfence from the age of 5 years	Each clinic visit
Clinical examination, eg skin, hair	Each clinic visit
Quantitative plasma amino acids (3-4 hours fasting)	Annual
Albumin, prealbumin	Annual
25-dihydroxyvitamin D	Annual
DEXA scan	Baseline DEXA scan at 11 years and repeat every 5 years, in the absence of osteopenia or osteoporosis
FBC, Plasma zinc, selenium, ferritin, folic acid, vitamin B	Annual
Essential fatty acids	Annual

References

Dixon MD, MacDonald A, White F, Stafford J. In: Clinical Paediatric Dietetics. 4th ed: West Sussex: John Wiley & Sons Limited, 2014:381-525.
Calcar S. Phenylketonuria. Bernstein et al (Ed) In: Nutrition Management of Inherited Metabolic Diseases. 1st ed: Springer International Publishing Switzerland 2015

Diet calculations of a newly diagnosed infant^1,2,3,4DiagnosisPKU

Plasma levels at initiation:
≥ 900 μmol/l	80-100% Phe free infant formula; 0-20% breast milk or infant formula. The PHE source (breast milk of infant formula) is temporarily stopped and replaced by a PHE free infant formula of 150 ml/kg/day, which will cause a rapid fall in PHE levels. Once PHE concentrations are below 1000 μmol/l, standard infant formula of breast milk is reintroduced.
500 – 900 μmol/l	70-90% Phe free infant formula ; 10-40% breast milk or infant formula. The breastmilk or standard infant formula is given by appr 50 mg/kg/day
<500 μmol/l	25- 50% Phe free infant formula; 50–75 % breast milk or infant formula PHE concentrations should be monitored weekly to ensure concentrations below 400 µmol/l before dietary management is started.
Protein recommendation	Age adequate and based on bodyweight
Energy provision	Age adequate and based on bodyweight
Volume	Age adequate and based on bodyweight 6-8 feeds in 24 hours/on demand
PHE free infant formula	Standard solution: 15 grams (or 3 scoops) PKU Anamix Infant or PKU 1-mix+ 90 mls water provides 100 ml PHE free formula
Breast feeding	Mostly 6-8 feeds are advised daily. Once blood PHE levels are stabilized within target range, if PHE concentration increases >360 µmol/l, the PHE free infant formula is increased by 10 ml per feed and the amount of breast feed decreases accordingly. If PHE concentrations are <120 µmol/l, the infant free formula is decreased by 10 ml per feed, and breast milk increased with the same quantity. Techniques for breastfeeding Fixed frequency of breast feeding and PHE free formula alternating PHE free formula prior to each breast feeding Measured expressed breast milk The volume will vary according PHE levels, age of diagnosis and frequency of breast feeds.
Standard infant formula	Preparation of the standard infant formula as indicated.Mostly 6-7 feeds are advised daily, the total daily amount is divided by the amount of feeds. Techniques for bottle feeding Start with the standard infant formula feed to ensure the full amount of PHE is provided
Frequency of monitoring	Plasma PHE concentrations daily Reducing to 2-3 times a week Weighing: daily
Increasing Phe intake	Increase amount of standard formula Or increase frequency of feeding or volume of breast milk
Transition to solid products/weaning	In line with recommendations on food introduction for healthy population Ensure total PHE level intake will stay in line with tolerance during introduction of PHE containing solid foods Start the introduction on low protein foods gradually in line with local recommendations, like vegetables and fruits Provide the low protein foods after the breast milk or formula feeds Manage energy intake, low protein foods contain often lower energy density than breast or bottle feeds Once 8 – 12 tablespoons are consumed at one time, this can be given instead of the equivalent of the standard infant formula or breast feed. Gradually introduce more texture and lumpier foods, starting at 6-8 months Finger foods can be introduced from 7 months onwards. From 9 months the low protein pasta, low protein bread and potato (products) can be introduced.

References

Dixon MD, MacDonald A, White F, Stafford J. In: Clinical Paediatric Dietetics. 4th ed: West Sussex: John Wiley & Sons Limited, 2014:381-525.
MacDonald A, Evans S, Cochrane B et al. Weaning infants with phenylketonuria: a review. J Hum Nutr Diet, 2012, 25 3−10.
MacDonald A, Rylance G, Asplin D et al. Abnormal feeding behaviours in phenylketonuria. J Hum Nut Diet, 1997, 10 163−70.
Van Spronsen Fj, van Rijn G. In: Dieet bij metabole ziekten. 1st: WKZ/UMCU Utrecht. 2011

PKU: Monitoring