Uric Acid Test

Hyperuricaemia is a condition characterised by high levels of uric acid in blood. An enzyme xanthine oxidase is responsible for breaking down the nucleic acid purine in body, leading to uric acid formation. Two-thirds of this uric acid is excreted by kidneys through urine, while the rest is metabolised by intestinal bacteria.  The concentration of uric acid in blood rises due to kidney dysfunction or increased purine intake. Similarly, if purines are not metabolised properly, it may lead to decreased levels of uric acid. Uric acid levels in the blood serum or urine are tested in the following conditions:

• Joint pain and soreness
• Swelling of the big toe, ankle and knees
• Hereditary deficiency of the xanthine oxidase enzyme
• Blood in urine
• Kidney disease
• Renal stones
• Polycythaemia
• Certain types of cancers such as myeloma
• Hyponatraemia (high sodium levels)
• Type 2 diabetes
• High blood pressure

Overweight patients with insulin tolerance are at a risk of developing uric acid stones mainly because of the excretion of important dietary constituents and due to the production of acidic urine.

Uric acid test is a simple procedure and it does not need any special preparations. No fasting is required before uric acid testing, and the blood test can be done anytime.

For urine analysis, it is necessary to collect the sample over a period of 24 hours. In these cases, the pathology laboratory provides the patient with a collection container coated with a preservative.

One should inform the pathologist and doctor about the type of diet and medication they are taking before undergoing this test.

A blood sample for uric acid test is collected from a vein in the arm using a small needle puncture. You may experience momentary pain at the site of needle insertion but otherwise, the whole procedure is risk-free. Blood is collected in a sterile tube or vial and subjected to biochemical analysis.

In case of urine analysis for the presence of uric acid, urine sample is collected by the patient over 24 hours. One should empty their bladder completely the first time after waking up without collecting the sample and then collect the urine for the next 24 hours.

The 24-hour samples are sent to the laboratory for analysis. Presence of uric acid may also be tested in a renal stone that is extracted through surgery or passed through urine.

In some cases, it is necessary to test the synovial fluid.

Normal results: A concentration of less than 6 mg/dL in the blood is normal for women and less than 7 mg/dL for men. Normal values for a urine sample may be as follows:

• For a normal diet: 250-750 mg/24 hours.
• For a purine-free diet: <400 mg/24 hours.
• For a high-purine diet: <1000 mg/24 hours.

Normal results for both blood and urine analyses suggest that uric acid is being properly metabolised in the body and kidneys are functioning optimally to excrete uric acid from the body.

Abnormal results: Results indicating excess or less concentration of uric acid in blood and urine indicate the presence of certain health conditions or risk of some disorders. The following conditions may be present if uric acid levels are high:

• Kidney failure
• Gout
• Leukaemia and metastatic cancer
• Haemolytic anaemia
• Hypothyroidism
• Lead poisoning                      

High uric acid levels in blood also indicate cardiovascular risk. Apart from these conditions, a purine-rich diet containing seafood, red meat, shellfish and liver and some drugs, such as diuretics, niacin and aspirin, may also result in increased levels of uric acid. Uric acid levels that appear lesser than normal, suggest the following conditions:

• Enzyme xanthine oxidase deficiency
• Drugs, such as allopurinol, probenecid and warfarin
• Renal tubular defects
• Liver disease
• Wilson’s disease
• Diet deficient in purines

In conclusion, uric acid is an important endogenous substance in blood, and uric acid test determines its concentration in blood and urine. Abnormally high or low levels indicate a disturbance in metabolism. Regular monitoring of uric acid in blood serum and urine can help diagnose many diseases, and an appropriate correlation can be sought by performing ancillary tests.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is purely from an educational perspective and is in no way a substitute for medical advice from a qualified doctor.