what is leuk
Leukocyte esterase. Leukocyte esterase (LE) is an esterase (a type of enzyme) produced by leukocytes (white blood cells). A leukocyte esterase test (LE test) is a urine test for the presence of white blood cells and other abnormalities associated with infection. White blood cells in the urine usually indicate a urinary tract infection (UTI).