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Pyuria is the condition of urine containing white blood cells or pus. Defined as the presence of 6-10 or more neutrophils per high power field of unspun, voided mid-stream urine, it can be a sign of a bacterial urinary tract infection. Pyuria may be present in people with sepsis, or in older people with pneumonia.
The leukocyte esterase test indirectly detects the presence of leukocytes (white blood cells) in urine which can be associated with a urinary tract infection. In the elderly, the leukocyte esterase test is often positive even in the absence of an infection.
Typically, most white blood cells (WBCs) in urine are neutrophils. They are round, larger than RBCs, possess a cell nucleus , and have a granular appearance. A few white blood cells can normally be found in the urine of healthy individuals; females tend to have slightly more than males.
In urine cytology, collected urine is examined microscopically. One limitation, however, is the inability to definitively identify low-grade cancer cells and urine cytology is used mostly to identify high-grade tumors. [4] If the test detects atypical or cancerous cells, further tests may be recommended, such as cystoscopy and a CT scan.
Neutrophils are the most abundant white blood cells in the human body (approximately 10 11 are produced daily); they account for approximately 50–70% of all white blood cells (leukocytes). The stated normal range for human blood counts varies between laboratories, but a neutrophil count of 2.5–7.5 × 10 9 /L is a standard normal range.
The test for leukocyte esterase is purely indicative and should not be solely relied on for diagnosis, as it does not replace microscopic or urine culture examinations. [19] The urine test strip reaction is based on the action of leukocyte esterase in catalysing the hydrolysis of an ester of indolecarboxylic acid.
There are four types of granulocytes (full name polymorphonuclear granulocytes): [3] Basophils; Eosinophils; Neutrophils; Mast cells; Except for the mast cells, their names are derived from their staining characteristics; for example, the most abundant granulocyte is the neutrophil granulocyte, which has neutrally staining cytoplasmic granules. [4]
Reference ranges for urine tests are described below: Measurement Lower limit Upper limit Unit ... Leukocytes: n/a: 0 / negative [2] See also. Reference range;