Urine
Dysbiosis organic acid screening
Measures organic acids in urine. Detects bacterial and yeast overgrowth.
€ 195,00
All tests
Sugar and metabolism · Urine
p-Hydroxyphenylacetic acid
A breakdown product of the amino acid tyrosine, partly made by gut bacteria; the value depends on diet.
At a glance
- Measured in urine
- In 1 test panel
- Check the preparation
Explanation
p-Hydroxyphenylacetic acid: what is measured?
p-Hydroxyphenylacetic acid (4-hydroxyphenylacetic acid) is formed when the amino acid tyrosine is broken down, partly in your own body and partly by gut bacteria. Plant substances from food can also be converted into this substance. It is excreted in the urine.
What can it detect?
- A snapshot of excretion, which mainly says something about recent diet, supplements, medicines and the activity of gut bacteria
- Rarely: an inherited metabolic disease, such as an organic aciduria (buildup of organic acids due to an enzyme deficiency) or a mitochondrial disease (a disorder of the cell's energy production); these are almost always discovered in childhood
Result
What does the result mean?
p-Hydroxyphenylacetic acid too high
A raised value is usually caused by a protein-rich diet, plant-based food or the activity of gut bacteria. The value can also be higher with an overgrowth of bacteria in the small intestine, but the test is not suitable for diagnosing this. A raised value does not cause symptoms by itself. Rarely, a strongly raised value, together with other abnormalities, fits an inherited disorder in the breakdown of tyrosine.
p-Hydroxyphenylacetic acid too low
For these substances, a low value usually has no meaning and does not cause symptoms. Low excretion can be caused by diluted urine, by low intake of the substance from food or by ordinary day-to-day fluctuations. For none of these substances is a low value in urine a recognized sign of a deficiency or disease. For substances that come from food or gut bacteria, a low value mainly says something about what was eaten recently.
After an abnormal result
A slightly abnormal value in someone without symptoms usually does not lead to further tests; the GP mainly looks at diet, supplements, medicines and the circumstances of collecting the sample. Only with a clearly abnormal pattern together with matching symptoms does the GP consult or refer to an internist or pediatrician with experience in metabolic diseases, who has the test repeated in a specialized laboratory if needed.
Reliability
How reliable is the test?
In the Netherlands, organic acids in urine are measured in specialized laboratories for metabolic diseases, such as those of the university medical centers (UMCs), at the request of a specialist when an inherited metabolic disease is suspected, usually in children. According to the American laboratory standard (ACMG), the result is then assessed as a pattern of several substances, together with symptoms, diet and medicines, and not substance by substance. As a 'functional' profile for adults without symptoms, to assess deficiencies, gut fermentation or the energy balance of the cells, the test is not validated.
What can affect the result?
- Diet in the days before the test has a large effect, for example fruit, fruit juice and wine, products with the preservative benzoic acid (E210 to E213), tea and coffee.
- Supplements and medicines, such as vitamins, paracetamol, aspirin, ibuprofen and epilepsy medicines, can add extra substances to the urine or shift values.
- Time of day, fasting, exercise, how concentrated the urine is and how long the sample is in transit without cooling (bacteria in the tube make substances themselves) affect the result.
- Laboratories use different methods and reference values; results from different laboratories are hard to compare.
Preparation
- Do not eat for 8 hours before collecting the sample. Do not drink much the evening before, no more than 300 to 500 ml.
- Collect the first morning urine, the middle part of the stream.
- Stop taking supplements 2 days beforehand.
- The day before, do not eat fruit, tomatoes, avocado, nuts or pumpkin and do not drink soft drinks or wine.
- Do not collect urine during your period.
Who it is for
Who is the test useful for?
Useful for
In hospitals, a specialist requests this test when there is a specific suspicion of a metabolic disorder, usually in a child with matching symptoms, and has it done in a specialized laboratory. For adults without symptoms, or to assess gut health, nutritional deficiencies or energy, the test is not useful according to current knowledge. Even with symptoms such as tiredness or abdominal complaints, it has not been shown that the result reveals the cause.
How common is it?
Each inherited metabolic disease on its own is rare. In the Netherlands, the heel prick screening finds, for example, 1 to 2 children with methylmalonic acidemia per year and about 1 child with propionic acidemia or glutaric aciduria type 1. There are no Dutch figures on abnormal values of individual organic acids in adults without symptoms.
RIVM, heel prick screening (pns.nl)
Get tested
p-Hydroxyphenylacetic acid: test panels
p-Hydroxyphenylacetic acid is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and results- UMC Utrecht, Bepalingenwijzer: Organische zuren (urine)
- ACMG technische standaard: Laboratory analysis of organic acids, 2018 update (Gallagher e.a., Genetics in Medicine)
- Verbeke e.a., Towards microbial fermentation metabolites as markers for health benefits of prebiotics (Nutrition Research Reviews, 2015)
- Erfelijkheid.nl: Stofwisselingsziektes
- RIVM, Hielprik: ziekten die de hielprik opspoort