To detect high levels of uric acid, which could be a sign of the condition gout, or to monitor uric acid levels when undergoing chemotherapy or radiotherapy; to detect high levels of uric acid in the urine in order to diagnose the cause of kidney stones and to monitor those with gout who are at risk of developing such stones. Uric Acid is also measured as part of the assessment of pre-eclampsia.
Uric Acid Test
None may be needed however some institutions recommend fasting. Follow any instructions you are given.
Uric acid is produced by the breakdown of purines, which are nitrogen-containing compounds found in the body in substances such as nucleic acids (DNA, RNA). They enter the circulation from digestion of certain foods, drinks (alcoholic beverages like beer and wine) 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 stools.
If too much uric acid is produced or not enough is excreted, it can accumulate in the body and cause increased levels in the blood (hyperuricemia). 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 accumulation of too much uric acid is due to either increased production, decreased elimination or a combination of both. Increased production can be caused by, for example, increased cell death, as may be seen with some cancer treatments, or, rarely, may be due to an inherited tendency to overproduce uric acid. Decreased elimination of uric acid is often a result of impaired kidney function due to kidney disease. In many cases, the exact cause of excess uric acid is unknown. Doctors seldom 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 the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in your arm. A 24-hour urine sample may be collected for urine uric acid measurement.
Is any test preparation needed to ensure the quality of the sample?
None may be needed however some institutions recommend fasting. Follow any instructions you are given.
How is it used?
The uric acid test is used to detect high levels in blood when gout is suspected. 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?
Uric acid is requested when a doctor suspects high levels of uric acid in blood. Some patients with high levels of uric acid have a disease called gout, which is an inherited disorder that affects purine breakdown. Patients with gout suffer from joint pain, most often in their toes but in other joints as well. The test may also be requested if a patient appears to have kidneys that are not working properly.
The test is also used as a monitoring tool when a patient has undergone chemotherapy or radiotherapy, to find out 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.
Urine uric acid may be requested when a person suffers from recurrent kidney stones or has gout and needs to be monitored for formation of these stones.
What does the test result mean?
Higher than normal uric acid levels in the blood is called hyperuricemia and can be caused by the over-production of uric acid in the body or the inability of the kidneys to clear out enough uric acid. The doctor will need to investigate further to determine the cause of the overproduction or decreased excretion of uric acid. There are several genetic inborn errors that effect purine metabolism. Metastatic cancer, multiple myeloma, leukaemias, and cancer chemotherapy can cause increased production of uric acid. Chronic renal disease, acidosis, toxaemia of pregnancy, and alcoholism can cause decreased excretion.
Increased concentrations of uric acid can cause crystals to form in the joints, which leads to the joint inflammation and pain characteristic of gout. Hyperuricaemia is the most important risk factor for gout, but serum levels should only be considered in combination with other clinical features of gout, since on its own it does not confirm or exclude this as the diagnosis. Many patients with hyperuricaemia do not develop gout while serum levels can be normal during an acute attack. 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 results seen in the healthy population 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 within the bloodstream.
In November 2012, the British Society for Rheumatology introduced new, user friendly, guidelines for diagnosis of Gout in Primary care.
Low levels of uric acid in the blood are seen much less commonly than high levels and are seldom considered cause for concern. Although low values can be associated with some kinds of liver or kidney diseases, Fanconi syndrome, exposure to toxic compounds, and rarely as the result of an inherited metabolic defect (Wilson’s disease), these conditions are typically identified by other tests and symptoms and not by an isolated low uric acid result.
High uric acid levels in the urine are seen with gout, multiple myeloma, metastatic cancer, leukaemia and a diet high in purines. Those at risk of kidney stones who have high uric acid levels in their urine may be given medication to prevent stone formation. Low urine uric acid levels may be seen with kidney disease and chronic alcohol use.
Is there anything else I should know?
Many drugs can increase or decrease the level of uric acid. In particular, thiazide diuretics can cause uric acid levels to rise.
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.
Some people may have a high level of uric acid in the blood without having associated signs or symptoms (asymptomatic hyperuricemia). However, general screening to detect this condition is not recommended, nor is treatment considered appropriate.
If I have high levels of uric acid, can they be lowered easily or will I have to take drugs for the rest of my life?
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.
What is gout?
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 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.
My uric acid level is high but I don't have gout. What does this mean?
High levels of uric acid in the blood do not always lead to symptoms. This condition, called asymptomatic hyperuricemia, is fairly common, with about 10% of adults having a high uric acid level with out accompanying symptoms at some point in time. In fact, most people with high uric acid will never develop symptoms. However, a few go on to experience symptoms of gout and complications such as kidney stones or some degree of kidney disease. It is generally thought that this condition does not require any follow up or treatment unless the affected person is at a high risk of complications. People with family members who have had gout, kidney stones or kidney disease due to hyperuricemia may receive treatment even though they are not experiencing symptoms.
Some studies have pointed to high uric acid as a risk factor for conditions such heart disease. It is also thought to play a role in diabetes, unhealthy lipid levels, high blood pressure, strokes and pre-eclampsia though the link between these diseases and high uric acid is not clear and somewhat controversial.
I heard women don't get gout. Is that true?
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.