Leukocyte esterase urine testWBC esterase
Leukocyte esterase is a urine test to look for white blood cells and other signs of infection.
How the Test is Performed
A clean-catch urine sample is preferred. The clean-catch method is used to prevent germs from the penis or vagina from getting into a urine sample. To collect your urine, the health care provider may give you a special clean-catch kit that contains a cleansing solution and sterile wipes. Follow instructions exactly so that the results are accurate.
After you provide a urine sample, it is tested right away. The provider uses a dipstick made with a color-sensitive pad. The color of the dipstick changes to tell the provider if you have white blood cells in your urine.
How to Prepare for the Test
No special steps are needed to prepare for this test.
How the Test will Feel
The test will involve only normal urination. 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. This may mean you have a urinary tract infection.
If this test is positive, the urine should be examined under a microscope for white blood cells and other signs that point to an infection.
A negative test result is normal.
The following may create a false positive result:
- Trichomonas infection (such as trichomoniasis)
- Vaginal secretions (such as blood or heavy mucus discharge)
False negative tests can be caused by:
- High level of protein
- High level of vitamin C
The examples above are common measurements for results of these tests. 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.
Gerber GS, Brendler CB. Evaluation of the urologic patient: history, physical examination, and urinalysis. In: Wein AJ, Kavoussi LR, Novick AC, Partin AW, Peters CA, eds. Campbell-Walsh Urology. 10th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 3.
McPherson RA, Ben-Ezra J. Basic examination of urine. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 28.
Sobel JD, Kaye D. Urinary tract infections. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 74.
Review Date: 8/14/2015
Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.