What is being tested?
Uric acid is produced by the breakdown of purines. Purines are chemicals that come from nucleic acids (DNA, RNA). They enter the circulation from digestion of foods or from normal breakdown and turnover of cells in the body. Most uric acid is removed by the kidneys and disposed of in the urine; the remainder is excreted in the faeces.
If too much uric acid is produced or not enough is excreted, it can accumulate. The presence of excess uric acid can cause the condition called gout – an inflammation that occurs in joints when crystals derived from uric acid form in the joint fluid. Excess uric acid can also lead to kidney disease, as a result of deposition in the kidneys or kidney stone formation, as a result of increased urinary excretion.
The most common reasons for accumulation of uric acid are an inherited tendency to overproduce uric acid or poor kidney function which gives decreased ability to excrete uric acid. Doctors don't need to test for low levels of uric acid.
Uric acid levels are also increased in pre-eclampsia and may be measured as part of the assessment of this condition.
How is it used?
The uric acid test is used to find out whether the body might be breaking down cells too quickly or not removing uric acid quickly enough. The test also is used to monitor levels of uric acid when a patient has had chemotherapy or radiation treatments.
Measurement of uric acid in urine is used to help diagnose the cause of recurrent kidney stone formation.
When is it requested?
The uric acid test is requested when a doctor suspects high levels of uric acid in blood. Most patients with raised levels of uric acid have no symptoms. Some patients with high levels of uric acid have a disease called gout, which causes joint pain and arthritis, most often in their toes but in other joints as well. The test may also be requested if a patient appears to have failing kidneys.
The test is also used as a monitoring test when a patient has undergone chemotherapy or radiation, to learn whether uric acid levels are getting dangerously high. Monitoring can also be done when a patient is found to have gout or renal failure. Patients who have high uric acid levels are sometimes put on drugs to help lower uric acid levels.
What does the result mean?
Higher than normal uric acid levels mean that the body is not handling the breakdown of purines well. The doctor will have to find out whether the cause is over-production of uric acid, increased intake of purine-rich food, or if the body is unable to remove the uric acid because the kidneys are not working properly.
Increased concentrations of uric acid can cause crystals to form in the joints, which leads to the joint inflammation and pain characteristic of gout. Uric acid can also form crystals or kidney stones that can damage the kidneys.
There has been some discussion among doctors about the exact limits of a ‘normal’ test result for uric acid. The range of normal results is wide. Uric acid levels can vary every day in the same patient or throughout the year.
Sometimes doctors will request several uric acid tests over a period of time to get a better idea of a patient’s level of uric acid.
Is there anything else I should know?
Many drugs can increase or decrease the level of uric acid. In particular, thiazide diuretic can cause uric acid levels to go up.
Aspirin (and other salicylates) have varying effects on uric acid. At low aspirin levels (as may occur in persons taking aspirin only occasionally), aspirin can increase blood uric acid. On the other hand, in high doses (as may be used to treat rheumatoid arthritis), aspirin actually lowers the concentration of uric acid.
For people who have uric acid kidney stones or gout, foods that are high in purine content should be avoided, including organ meats (like liver and kidneys), sardines and anchovies. Alcohol also should be avoided because it slows down the removal of uric acid from the body. Fasting, a starvation diet, and strenuous exercise all raise uric acid levels.
Common questions
Depending on the condition that causes your high levels of uric acid, you may not need to take drugs. If you have a sudden attack caused by high uric acid, as with an attack of gout, your doctor may treat you with the drug colchicine and a nonsteroidal anti-inflammatory drug, such as aspirin or ibuprofen. This treatment usually is short-term.
However, you may have to stay on a maintenance therapy for a few years, until your uric acid levels come under control. You may be given drugs such as probenecid that help to clear your system of uric acid salts or you may be given drugs that interfere with uric acid production, such as allopurinol.
If you have had chemotherapy or radiation, you may have to take uric acid tests more often and possibly treat the condition over time. A new medication, rasburicase, may be used for this.
Gout is one of the most common forms of arthritis. A gout attack usually happens at night, and within 12 or so hours there may be severe pain and swelling in the joint. Gout usually affects only one or two joints at the same time, typically in the feet and ankles. It often occurs in the big toe, and people can notice it at night when their bedding rubs on their toe and causes extreme pain. Gout happens when crystals derived from uric acid accumulate in the joints. These crystals cause inflammation.
Without treatment, an early attack of gout usually goes away in a week. It may be months or years until the next attack. As time goes by, more joints can become affected and become chronically swollen with urate crystals called tophi. Eventually the disease may cause disabilities or may eventually cripple the patient. That is why it is important to get treated right away if you think you may have gout. Your doctor will request a uric acid test and may have to take fluid from the joint through a needle to look for the microscopic crystals.
No. Gout affects mostly men, and it is very rare in women until after menopause, the time in life when a woman's monthly period stops and especially if they are taking diuretics. Gout in young women is extremely rare and needs special investigation.
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