The concentration of uric acid can be determined in the blood or urine. In excess, it is mainly a symptom of gout, excessive alcohol consumption, or kidney failure.
What is blood or urinary uric acid?
Uric acid is a waste product of the body. Specifically, it is the end product of the excretion of molecules called nucleic acids and purines.
Generally, most of the uric acid contained in the human body dissolves in the blood and joins the kidneys to be eliminated in the urine. But in some cases, the body produces excess uric acid or fails to eliminate enough. This condition can be the cause of various disorders.
Uric acid and diet
Since uric acid is the end product of the breakdown of purines, its level varies according to the purine content in the body. And it turns out that purines are found especially in the diet.
Some of the foods rich in purines to avoid:
- anchovies, herring, mackerel, sardines, shrimps, etc.;
- liver, heart, brain, kidneys, sweetbreads, etc.;
- peas, dried beans, etc.
The consumption of alcohol, especially beer, is not recommended when you want to reduce your uric acid.
On the contrary, among the permitted foods low in purine are:
- tea, coffee, and soft drinks;
- fruits and vegetables;
- bread and cereals;
- cheese and more generally dairy products
Why do a uric acid analysis?
The doctor prescribes a blood test (called uricemia) and/or a urine uric acid test for:
- detect gout;
- assess the proper functioning of the kidneys;
- it can also be requested in case of pregnancy;
- or overweight people.
It should be noted that the analysis of the concentration of uric acid in the urine will also provide a better understanding of the origin of a high level of uric acid in the blood.
Urin acid blood test
In the blood, the normal value of uric acid is between 35 and 70mg/L.
A higher concentration of uric acid in the blood is called hyperuricemia and can be caused by an over-production of uric acid in the body or a decrease in its elimination by the kidneys. Thus, high levels of uric acid in the blood can be a sign of:
- gout (this is the main cause of increased uric acid levels in the blood)
- an excess of degradation of the body’s proteins that takes place, for example, during chemotherapy, leukemia, or lymphoma;
- excessive physical exercise;
- the presence of kidney stones;
- rapid weight loss;
- a diet rich in purine;
- preeclampsia during pregnancy
- or kidney failure.
On the contrary, it is possible that the blood uric acid level is lower than normal, but this is a rarer condition than the scenario where it is higher.
Thus, uric acid levels below normal values may be related to:
- a diet low in purines;
- Wilson’s disease (a genetic disease characterized by a buildup of copper in the body)
- kidney (such as Fanconi syndrome) or liver damage
- or exposure to toxic compounds (lead).
In urine, the normal value of uric acid is between 250 and 750 mg/24 hours.
Note that normal values may vary slightly depending on the laboratories performing the analyses.
Affecting 5 to 15% of the population, it is a frequent biochemical abnormality, resulting from an overproduction of uric acid and/or decreased renal elimination. It often develops painlessly and is therefore not always immediately diagnosed.
High uric acid levels can be explained by:
Idiopathic or primary hyperuricemias
They account for the vast majority of cases. Hereditary predispositions are found in 30% of subjects, but they are often associated with obesity, overeating, high blood pressure, alcohol abuse, diabetes, and hypertriglyceridemia.
Rare enzyme abnormalities
They are found in particular in Von Gierke disease and Lesch-Nyhan disease. These enzymatic abnormalities have the particularity of causing attacks of drops very early, that is to say in the first 20 years of life.
Hyperuricemias secondary to disease or drug treatment.
These hyperuricemias may be due to:
– a defect in the elimination of uric acid. This is the case for kidney failure, but also because of certain drugs (diuretics, but also laxatives, and some anti-tuberculosis drugs).
– an increase in the degradation of nucleic acids. We see this in blood diseases (leukemias, hemopathies, hemolytic anemias, extensive psoriasis), and in the aftermath of certain cancer chemotherapy.
The consequences of hyperuricemia
Hyperuricemia can cause two types of problems:
- Gout is responsible for inflammatory-type joint pain.
When the uric acid microcrystals dissolved in the blood are in too high a concentration and local conditions are favorable (including sufficient acidity of the medium), they precipitate and lead to local inflammation. This preferentially affects the joint of the big toe. Only 1 in 10 people with too much uric acid in their blood will become gouty, so it takes extra susceptibility to get it.
They are due to the presence of one or more stones in the urinary tract and are responsible for renal colic. Urolithiasis is a very common disease since 1 to 2% of the population is affected in France.
How does the analysis work?
The single acid level can be analyzed in the blood and/or urine:
- the blood test consists of a venous blood sample, usually from the crease of the elbow;
- The level of uric acid in the urine is measured for 24 hours: to do this, it is enough to urinate in a container provided for this purpose and provided by the medical staff for a day and a night.
Note that it is advisable not to eat or drink anything during the hours before the test.
What are the factors of variation?
Many factors can cause uric acid levels to vary in the blood or urine. These include:
- foods (poor or high in purines);
- medications (to sign gout, aspirin, or diuretics);
- age, with children with lower values;
- gender, with women, generally have lower rates than men;
- weight, obese people with a higher rate.
Drug treatments if hyperuricemia is symptomatic are:
- Nucleic acid synthesis reducers, such as allopurinol. You have to be very careful because there are many interactions with other drugs.
- Drugs that inhibit renal reabsorption of uric acids, such as benzbromarone.
- Enzyme treatments often cause allergy problems.
Whatever happens, it is the doctor who must decide whether a treatment should be followed, and which one is the most suitable.
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