A urinary tract infection (UTI) test aims to detect bacteria or other microorganisms in the urinary system. A “false positive” result occurs when a test indicates a UTI is present, but an actual infection does not exist. This misdiagnosis can lead to unnecessary antibiotic treatment, contributing to antibiotic resistance and potential side effects. Understanding the factors that cause such inaccuracies is important for accurate diagnosis and appropriate care.
Common Contamination Issues
One of the most frequent reasons for a false positive UTI test is contamination of the urine sample during collection. The human body naturally harbors bacteria on the skin, around the genital area, and in the rectum. If these external bacteria enter the urine sample, they can lead to a positive test result even if the urinary tract itself is free of infection.
Skin bacteria, for instance, can easily transfer to the collection cup if proper hygiene and collection techniques are not followed. Vaginal discharge, which often contains various microorganisms and cells, can also mix with the urine, leading to elevated white blood cell counts or bacterial presence on the test, mimicking an infection. Similarly, fecal matter contains a high concentration of bacteria, including E. coli, a common cause of UTIs, and even a small amount can contaminate a sample, producing a false positive result.
Improper collection techniques, such as not performing a “clean catch,” significantly increase the likelihood of contamination. A clean catch involves cleaning the genital area thoroughly and collecting a midstream urine sample, meaning the initial flow of urine is discarded to flush out contaminants from the urethra. If this procedure is not followed, external bacteria or cells can lead to a positive result for indicators like leukocytes (white blood cells) or nitrites, which are typically associated with a UTI. A urine culture showing multiple types of bacteria, especially at lower colony counts, often suggests contamination rather than a true infection.
Medications and Nutritional Factors
Certain substances ingested through medications or diet can also alter urine composition, leading to false positive results on UTI tests. Some medications are known to directly interfere with the chemical reactions on urinalysis test strips. For example, phenazopyridine, a common over-the-counter medication used to relieve UTI symptoms, can turn urine a reddish-orange color, which may cause a false positive for blood on a dipstick test. Similarly, high doses of certain vitamins, particularly Vitamin C (ascorbic acid), can influence urine test results.
Non-UTI Medical Conditions
Several medical conditions unrelated to bacterial UTIs can produce markers or symptoms that mimic an infection, leading to a false positive test result. Conditions like kidney stones can cause blood to appear in the urine (hematuria) due to irritation or damage to the urinary tract lining. While blood in the urine can be a sign of a UTI, its presence from kidney stones would result in a false positive for infection indicators.
Interstitial cystitis, a chronic bladder condition characterized by bladder pressure, pain, and sometimes pelvic pain, can cause symptoms very similar to a UTI, such as frequent urination and urgency. However, it is an inflammatory condition and does not involve bacterial infection, yet it might cause an increase in white blood cells in the urine, leading to a false positive for infection.
Asymptomatic bacteriuria, which is the presence of bacteria in the urine without any symptoms of infection, is another common scenario. In these cases, a urine test will show bacteria, but because there are no symptoms, treatment is often not needed, yet the test result would be positive.
What to Do After a Positive Result
If you receive a positive UTI test result, especially if you are not experiencing typical UTI symptoms like painful urination, frequent urges, or burning, it is important to consult a healthcare provider. Discussing your symptoms, or the lack thereof, provides important context. Your healthcare provider will consider your medical history, current medications, and any other conditions.
Often, a preliminary positive result from a rapid test like a dipstick may lead to a confirmatory urine culture. A urine culture is a more definitive test that identifies the specific type and quantity of bacteria present in the sample, helping to differentiate between actual infection and contamination. It also helps determine which antibiotics would be most effective if an infection is indeed present.
It is important to avoid self-treating with antibiotics based solely on a preliminary positive result, as this can contribute to antibiotic resistance and may not address the underlying cause of your symptoms.