page_title: Urine test strip
section_title: Leukocytes test
hierarchical_section_title: Urine test strip / Diseases identified / Urinary infections / Leukocytes test
caption_attribution_description: English: Sample of urine from a patient with urinary infection. It's possible recognize epitelial cells, red blood cells and leukocytes
context_page_description: A urine test strip or dipstick is a basic diagnostic tool used to determine pathological changes in a patient's urine in standard urinalysis.
  A standard urine test strip may comprise up to 10 different chemical pads or reagents which react when immersed in, and then removed from, a urine sample. The test can often be read in as little as 60 to 120 seconds after dipping, although certain tests require longer. Routine testing of the urine with multiparameter strips is the first step in the diagnosis of a wide range of diseases. The analysis includes testing for the presence of proteins, glucose, ketones, haemoglobin, bilirubin, urobilinogen, acetone, nitrite and leucocytes as well as testing of pH and specific gravity or to test for infection by different pathogens.
  The test strips consist of a ribbon made of plastic or paper of about 5 millimetre wide, plastic strips have pads impregnated with chemicals that react with the compounds present in urine producing a characteristic colour. For the paper strips the reactants are absorbed directly onto the paper. Paper strips are often specific to a single reaction, while the strips with pads allow several determinations simultaneously.
context_section_description: It is normal to find up to 3 (occasionally 5) leukocytes per high power field (40X) in a urine sample, with women having slightly higher results owing to vaginal contamination. Higher numbers indicate urinary infection. The urine test strip test for white blood cells detects leukocyte esterase, which is present in azurophilic granules of monocytes and granulocytes (neutrophilic, eosinophilic and basophilic). Bacteria, lymphocytes and epithelial cells from the genitourinary tract do not contain esterases. Neutrophil granulocytes are the leukocytes most commonly associated with urinary infections. A positive test for leukocyte esterase normally indicates the presence of bacteria and a positive nitrite test (although it is not always the case). Infections caused by Trichomonas, Chlamydia and yeasts produce leukocyturia without bacteriuria. The inflammation of the renal tissues (interstitial nephritis) can produce leukocyturia, in particular toxic interstitial nephritis with predominant eosinophils.
  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.
  The urine test strip reaction is based on the action of leukocyte esterase in catalysing the hydrolysis of an ester of indolecarboxylic acid.  The indoxyl that is liberated combines with a diazonium salt in order to produce a violet coloured azole dye.
  1) Reaction catalysed by leukocyte esterase 
  2) In acid medium 
  The esterase reaction needs about 2 minutes to take place. The presence of strong oxidising agents or formaldehyde can cause false positives. False negative results are associated with elevated concentrations of protein (greater than 500 mg/dL), glucose (greater than 3 g/dL), oxalic acid and ascorbic acid. Urine with a high specific gravity can also cause leukocyte crenation, which can impede the liberation of the esterases.
caption: A sample of urine sediment from a patient suffering from a urinary infection, it is possible to see leukocytes (small round and  granular), erythrocytes (small round and biconcave) and epithelial cells (large and polyhedral). The test for leukocyte esterase is indicative and does not replace microscopic examination of urine.[19]
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