What Does Leukocyte Esterase Mean on a Urine Test?

What it means

Leukocytes are white blood cells, the cells that fight infection. Leukocyte esterase is an enzyme they carry. A urine dipstick has a small pad that changes colour when this enzyme is present, so it acts as an indirect sign that white cells are in the urine.

White cells gather where there is infection or inflammation, so this line is mainly there to help spot a urinary tract infection. The writer of the report is flagging that white cells may be present; it is usually read together with nitrites, symptoms and sometimes a urine culture, which grows any bacteria and identifies them.

It is not the same as a white cell count in the blood. It is also different from the 'WBC' or 'pus cells' count on urine microscopy, which counts the cells directly instead of detecting their enzyme.

Where you may see it

• Urine dipstick results in GP, urgent care or emergency notes
• The 'Chemistry' part of a urinalysis report, often shown as trace, 1+, 2+ or 3+
• Antenatal check-up urine results
• Lab reports that trigger a reflex urine culture