Uric Acid Test: What This Test Is and How It Is Done

A referral for a uric acid test looks ordinary: a line on a biochemistry form or a slip from a rheumatologist. Behind it is a test that explains why a joint hurts or where kidney stones come from.

Uric Acid Test: What This Test Is

Uric acid is the end product of purine metabolism in humans; it is formed when xanthine is oxidized. Purines appear when cells die and come in with food and drinks. Normally the acid dissolves in the blood, is filtered by the kidneys, and is excreted in urine.

The test measures its amount in blood or urine. Other names also appear on forms: serum urate, UA, serum uric acid.

Why Uric Acid in the Blood Is Measured

Most often a blood uric acid test is ordered for signs of gout, usually together with synovial fluid analysis. The second reason is monitoring in people on chemotherapy: when treatment rapidly destroys tumor cells, a lot of purines enter the blood.

The test is offered when kidney stones are suspected, in metabolic syndrome, and when taking diuretics.

How the Test Is Taken and How to Prepare for It

Blood is drawn from a vein in the arm with a thin needle, and a small amount of blood is placed in a tube. The procedure takes less than five minutes, and this test has no known risks.

The urine test is a 24-hour collection: all urine over 24 hours is collected in a special container and kept cold. The start time is recorded, and the first portion is not put into the container.

According to recommendations: before the test, tell your doctor about all medications. Aspirin, niacin (vitamin B-3), and some other agents change the result, but you must not stop taking them on your own — this is discussed in advance.

Uric Acid in a Blood Chemistry Panel

The marker is part of a blood chemistry panel. Reference ranges: in men — no more than 420 µmol, in women — no more than 360 µmol. An excess is called hyperuricemia; according to existing estimates, it occurs in about one third of the world's population.

A number above the reference range is not yet a diagnosis. Deposition of sodium urate crystals in joints is gout, but not everyone with an elevated level develops it.

What the Results Mean and When the Level Falls Outside the Normal Range

A high blood level occurs when the body makes too much acid or the kidneys cannot keep up with excreting it. Among the causes are foods rich in purines:

• red meat and organ meats — liver, kidneys;
• shellfish, anchovies, sardines, trout, tuna;
• alcohol — any type;
• high-fructose corn syrup in sweet drinks and sweets.

An elevated level is associated with gout, kidney disease and stones, leukemia, myeloma, metastatic cancer, side effects of antitumor treatment, and preeclampsia. Low blood numbers are rare and usually not harmful. A high urine level occurs in gout, stones, and obesity.

When a Doctor Is Needed and Why the Marker Should Be Monitored

A reason to see a doctor is sudden severe joint pain, swelling, redness, and heat of the skin over it. The big toe is most often affected; other toes, the ankle, and the knees can also be involved; signs usually appear in one joint.

A uric acid deviation by itself is not a reason to call an ambulance. 103 or 112 — if sudden joint pain and swelling are accompanied by worsening pain, very high fever, chills, nausea, or inability to eat: this may be an infection inside the joint.

Without treatment, a gout attack lasts from one to two weeks, subsequent ones are longer, and over time persistent joint changes appear. With long-standing gout, tophi develop on the ears, fingers, and elbows, and kidney stones form.

The doctor asks about diet and alcohol, may refer you to a rheumatologist, and order synovial fluid analysis or scanning. Monitoring is needed for people on antitumor treatment and for those whose gout is combined with kidney stones.

Bring your form to the appointment and write down questions: what is my level and what is it compared with; do I need to repeat the test and when; do my medications affect the result; is a blood test enough or is a 24-hour urine test needed. This material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer