After you have been asked to provide a mid-stream urine sample, a dipstick is applied to the urine to check for signs of infection or inflammation. This dipstick test strip is made of paper and can have up to 10 different chemical pads or reagents which react (change colour) when immersed in, and then removed from, a urine sample usually after around 60 seconds. The dipstick analysis includes testing for the presence of:
- White blood cells (known as Leukocytes) – only a few white blood cells are normally present in urine. When these numbers increase, the dip test will become positive. This indicates that there is inflammation in the urinary tract or kidneys and the body is excreting more white blood cells. White blood cells also produce antitoxins that neutralise the toxins released by bacteria.
- Red blood cells – the bladder can bleed due to severe inflammation and the constant urination caused by a UTI. Some people can feel a “razor blade sensation” when urinating during a UTI attack.
- Protein – the presence of protein can indicate a possible kidney infection as only trace amounts normally filter through the kidneys. Other causes of protein in the urine can include kidney disease, dehydration,
- Nitrites– Nitrite tests detect the products of nitrate reductase, an enzyme produced by some bacterial species that can cause a UTI. These products are not present normally unless a UTI exists. A positive result on the nitrite test is highly specific for UTI, typically because of urease-splitting organisms, such as Proteus species and, occasionally, E coli; however, it is very insensitive as a screening tool, as only 25% of patients with UTI have a positive nitrite test result. This occurs in cases with low bacterial colony forming unit counts, or in recently voided or dilute urine as it can take up to four hours before the urinary enzyme nitrate reductase is converted by bacteria in urine. In addition, a nitrite test does not detect organisms unable to reduce nitrate to nitrite, such as enterococci or staphylococci.
Any evidence of these in the urine on a dipstick test indicates bladder inflammation/infection.
Additionally, the dipstick reagent pads test for the presence of Bilirubin, Urobilinogen, Ketones and Glucose.
Find out more about how to interpret your urine dipstick test.