How the Test is Performed

A clean catch urine sample is needed. See: Urine specimen - clean catch

How to Prepare for the Test

No special preparation is necessary for this test.

How the Test Will Feel

The test will involve only normal urination, and there is no discomfort.

Why the Test is Performed

Leukocyte esterase is a screening test used to detect a substance that suggests there are white blood cells in the urine, which may mean you have a urinary tract infection.

This test is part of the routine urine dipstick test. If this test is positive, the urine should be examined under a microscope for white blood cells and other abnormalities associated with infection.

Normal Results

A negative test result is normal.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result indicates a possible urinary tract infection.

Considerations

The following may create a false positive result:

• Vaginal secretions (such as blood or heavy mucus discharge)
• Trichomonas infection (such as trichomoniasis)

False negative tests can be caused by:

• High levels of protein
• High levels of vitamin C

Alternative Names

WBC esterase

References

Landry DW, Bazari H. Approach to the patient with renal disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 116.

Ban KM, Easter JS. Selected urologic problems. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 97.

Litza JA, Brill JR. Urinary tract infections. Prim Care. 2010 Sep;37(3):491-507, viii.

Updated: 4/21/2012

Reviewed by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.