Leukocyte esterase

Leukocyte esterase is an enzyme produced by white blood cells (WBCs). The presence of leukocyte esterase activity in urine indicates that WBCs are present in the urinary tract, suggesting infection, inflammation, or other urinary tract pathology. This is commonly detected on urinalysis and is often the first sign of a urinary tract infection (UTI). Elevated levels warrant culture testing to identify the causative organism and determine appropriate antibiotic treatment. A positive result can also indicate kidney stones, interstitial cystitis, or other urological conditions.