Leukocytes in the urine may indicate infection, according to Mayo Clinic. Leukocyte esterase is a product of white blood cells and may indicate a urinary tract infection.
A laboratory technician performs a urinalysis with a visual exam, a dipstick test and a microscopic exam, explains Mayo Clinic. A dipstick is a thin, plastic stick with chemicals that change colors to indicate abnormalities in urine. The dipstick test checks for evidence of infection, including the presence of leukocyte esterase or nitrates. The laboratory technician looks for white blood cells, or leukocytes, during the microscopic exam. Urinalysis does not usually provide a definite diagnosis, and a patient may require additional testing.