What Is Leukocyte Esterase?

Leukocyte esterase is a specific enzyme contained in human leukocytes. This enzyme is commonly used in clinical practice to detect the presence of leukocytes in a specimen. But leukocyte esterase is only found in neutrophils, but not in other cells.

Leukocyte esterase (LE) is a specific enzyme contained in human leukocytes. When the human body undergoes an inflammatory response, the chemotaxis of multinucleated white blood cells accumulates in inflammatory lesions and releases a large amount of LE. LE hydrolyzes 5-bromo 4-Chloro-3-indole acetate, which releases bromoindolyl, which produces a color change under aerobic conditions, and the color depth is directly proportional to LE activity.

The urine specimens submitted for the test of leukocyte esterase must be fresh, so as to avoid the destruction of the white blood cells of the urine, which may cause artificial experimental errors of the dry chemical strip method and the microscopy method. Furanizidine can produce false positives; Pioneermycin, gentamicin, or urine contamination with formaldehyde can produce false negatives. Leukocyte esterase test results were low or negative when urine glucose or specific gravity increased and urine protein content was> 5 g / L. ^[2]

Negative ^[3]

Positive is seen in urinary tract infections, such as nephritis, urinary tract infections, and so on. Leukocyte esterase exists in the granulocyte cytoplasm. Due to renal transplant rejection or urinary tuberculosis, the enzyme is not present when lymphocytes appear in the urine, and the result is negative. When the number of urine granulocytes is greater than 0.5-15 cells / u, different levels of positive reactions can occur. At the same time, when urine leukocyte esterase is positive, nitrite is generally positive and urine pH is increased.

LE can be used as an indicator of vaginal mucosal damage. Clinically, the presence of white blood cells in the specimen is often detected by detecting the activity of LE in the secretion. Bacterial and fungal vaginosis can be seen in polymorphonuclear leukocytes significantly increased, so leukocyte esterase activity can reflect vaginal cleanliness, and assist in diagnosing the degree of vaginal inflammation. Negative "-" or suspicious "±": indicates that the vaginal mucosa is normal and no infection exists; positive "1 +": common before and after menstrual period and after medication; strong positive "2+": indicates that the vaginal mucosa is damaged and infection exists .

Leukocyte esterases in urine dry chemical analysis are mainly found in neutrophils and histiocytes, and they are very low in lymphocytes and monocytes. Urinary LEU is positive, indicating that the urinary system has purulent inflammation. Microscopic examination shows neutral Granulocytes, in some cases, when neutrophils are destroyed, the contents are released into the blood, and no cellular components can be seen under microscope observation, but LEU is still positive. In addition, LEU can also be positive when strenuous exercise or fever. But LEU-negative is not certain that there is no infection, such as urinary TB infection. When a kidney transplant patient has a rejection reaction, lymphocytes are predominant in the urine, and LEU usually shows negative results. In addition, when the concentration of bilirubin in the urine is too high, the formaldehyde is contaminated, and the urine contains a large amount of drugs such as cephalexin or gentamicin, the LEU may give a false positive result. ^[3]