Leukocyte esterase is a urine test to look for white blood cells and other signs associated with 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 health care provider uses a dipstick made with a color-sensitive pad. The color of the dipstick changes to tell the provider if you may have white blood cells in your urine.
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. 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.
Normal values vary from lab to lab. Talk to your doctor about the meaning of your specific test result.
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
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, et al., eds. Campbell-Walsh Urology. 10th ed. Philadelphia, Pa: Elsevier Saunders; 2011: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.
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, Bethanne Black, and the A.D.A.M. Editorial team.