Urinary Phenylacetate-to-Creatinine Ratio, 24-Hour Collection
Measures urinary phenylacetate relative to creatinine in urine collected for 24 hours. It may help assess phenylalanine metabolism in people with phenylketonuria.
["This test helps evaluate phenylalanine metabolism, particularly in monitoring people with phenylketonuria."]
Key facts at a glance
- LOINC
- 50358-1
- Short code
- Phenylacetate/Creat 24h Ur-sRto
- Synonyms
- Phenylacetate/Creat 24h Ur-sRto
- Category
- kidney
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test measures phenylacetate, a substance formed when the amino acid phenylalanine is broken down, relative to creatinine in a 24-hour urine collection. Creatinine is used as an adjustment for urine concentration.
Why might I need this test?
It may be used to monitor people with phenylketonuria, an inherited condition in which phenylalanine is not processed normally. It can provide information about phenylalanine metabolism and the effectiveness of dietary treatment.
How is the test performed?
You collect all urine produced for 24 hours according to the laboratory’s instructions. The laboratory measures phenylacetate and creatinine and calculates their ratio.
How do I prepare for the test?
Follow the laboratory’s collection instructions, including how to store the container and whether to refrigerate it. Record the total urine volume and bring the completed container to the laboratory as directed. Do not change your prescribed diet or phenylalanine intake unless your clinician advises you to do so.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
An elevated result may indicate increased phenylalanine breakdown or reduced phenylalanine processing, as can occur with inadequately controlled phenylketonuria or higher phenylalanine intake. Results should be interpreted with other metabolic tests, dietary information, and clinical findings. Collection errors and unusual urine creatinine levels can also affect the ratio.
Short name
24-Hour Urine Phenylacetate Ratio
Frequently asked questions
What does phenylacetate measure?
Why is creatinine included in the result?
How is a 24-hour urine collection done?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy