About Leukocytes (Urine)
Leukocyte esterase on a urine dipstick detects the enzyme released by white blood cells in the urine, indicating pyuria — the presence of white cells typically caused by a urinary tract infection, kidney infection, or inflammation. A positive leukocyte esterase should be interpreted alongside nitrite (which detects bacteria) and, if positive, confirmed with urine microscopy and culture. The combination of positive leukocyte esterase and nitrite has high sensitivity for a bacterial UTI.