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Leukocyte esterase
Definition:

Leukocyte esterase is a urine test to look for white blood cells and other signs associated with infection.
Alternative Names:

WBC esterase
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 Values:

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.
Special 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
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;37:491-507.
Review Date: 8/21/2011
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.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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