OTC UTI tests claim they can easily and quickly detect a urine infection. But are they accurate? Unfortunately, the research behind OTC UTI test is not bulletproof.
Although they are called UTI test strips, they were not created to detect a urine infection if you already have symptoms. In fact, if you have the classic burning, pain, and urgency, a UTI testing strip was not made for you. Surprisingly, this is because these UTI testing strips are screening tests, not diagnostics tests. To understand this let’s take a quick look at the difference between the two tests and how they are used.
OTC UTI Test Is For Screening, Not Diagnosing
Screening tests are for patients without symptoms
A screening test is exactly what it sounds like: it screens people for a disease. The caveat here is that it looks for disease in people who have no symptoms – think of mammogram screening for breast cancer.
Let’s look at that in action. A screening test, like an OTC UTI test strip, could screen pregnant women for a UTI. They are perfect screening candidates because while most pregnant women have no symptoms, it’s really important to catch a urine infection early as they can cause problems for both mom and a baby.
A screening test is very sensitive, meaning that if the test is negative, you can be confident you don’t have the disease. OTC UTI test strip is good at ruling out a disease. So, if a pregnant woman without any burning or urgency has a negative screening test, she can be pretty sure she does not have a UTI.
Diagnostic tests confirm diagnose in the patients with symptoms
A diagnostic test diagnoses people who are very likely to have the disease because they have common symptoms.
For example, a diagnostic test is perfect for a woman who has some classic symptoms of a UTI: goes to the bathroom 15 times a day, and has pain with urination. She could use an OTC UTI test strip, but the result will be less accurate.
OTC UTI test strip does not rule in disease. For that, you need a diagnostic test. Diagnostic tests are specific, if they are negative, you can be sure you don’t have the disease.
So if you already have UTI-like symptoms, you want to rule all other reasons before starting a treatment for UTI. For example, if you think you have a UTI when in fact you have a kidney stone, you waste precious time and resources taking antibiotics or herbal remedies that will do nothing to get rid of the stone. Diagnostic tests shine at weeding out all the people who are likely to have a disease but don’t.
Is an OTC UTI Test Accurate?
An OTC UTI test strip is pretty accurate if it is used for screening. The problem with the results arises when you use an over-the-counter UTI test strip to diagnose a UTI.
If you have UTI-like symptoms and rely on the test, you’re asking it to do something it was never meant to do. In fact, screening tests tend to “underdiagnose” if you have symptoms. That’s because a symptomatic person is at such a high risk for the disease that a screening test can miss them.
On the other hand, if you use an OTC UTI test in a group of people who have no symptoms, it will do much better to identify patients with bacterial overgrowth.
This is why UTI test’s “sensitivity” can change from 56% to 92% depending on who is being tested.
Research shows that the role of these tests should be to screen patients without any symptoms. The marketing ploys for over-the-counter UTI strips generally fail to mention this important fact.
How OTC UTI test works
OTC UTI test looks for indirect evidence of an infection. Instead of spying on the E. coli swimming around in your urine, it uses enzymatic tests that can be present if you have UTI causing bacteria in your urine.
Two common tests are the Greiss test, which checks to see if nitrate is reduced to nitrite, and the leukocyte esterase test, which is a marker for inflammatory cells (white blood cells) in your urine.
When these two tests are combined, researchers conclude that this combination is not good enough to be a screening test for UTIs. Unfortunately, this is the exact combination used in many over-the-counter UTI tests.
Why OTC UTI test could be inaccurate
There are several cases when an OTC UTI test could tell you that you have a UTI when you really don’t.
For example, if you have protein in your urine (kidney disease can cause this), use Vitamin C supplements or just used Azo, the leukocyte esterase test will be positive, even if you don’t have a UTI.
The Greiss test is only accurate for some bacteria, like E. coli. While most people with a UTI have E. coli, there are many have other bacteria. These folks would get a negative result on the over-the-counter UTI test when they really do have a UTI.
Is my OTC UTI test same as the one used by a doctor?
No, it’s not.
Despite the claims of over-the-counter UTI testing strip companies, it is not the same test your doctor uses. Rather it is a truncated version of your doctor’s test, that ignores important information about your urine.
For example, the urine test your doctor uses checks for more evidence of urine infection. It looks at the important factors that increase the sensitivity of the test and may suggest other reasons for your urinary symptoms:
- Your urine pH
- Endothelial cells
- Blood in the urine
How To Collect Urine For and OTC UTI test?
The process is similar to getting a urine test done at your doctor’s office:
- You will need to do a mid-catch urine: you place the strip into the urine stream a few seconds after you’ve already started urinating. This decreases the risk of contamination from the vagina or urethra.
- It is also important to clean your labia (or the tip of the penis) before doing the test.
So, how do I know for sure if I have a UTI?
If you’ve had UTIs before, you are well aware of the symptoms. Rather than buy UTI tests strips that are inaccurate, choose a better method.
You can choose to treat based on symptoms (with antibiotics or herbal alternatives) as long as you know the red flags (like fevers, back pain, vomiting) that mean you need to check in with your doctor.
How to get a diagnostic test for UTI
If you have UTI symptoms and must know for sure if it really is a UTI, choose a diagnostic test instead. The most widely available diagnostic test is a microscopic urinalysis and urine culture.
Generally, we look at your urine under a microscope (to look directly for bacteria, fungi, white blood cells, red blood cells and endothelial cells). Simply adding the urinalysis increases the sensitivity of urine testing to 96% . Then, we place the urine into a petri dish with bacteria-friendly growth medium and wait for the bacteria to grow.
Diagnostic UTI test tips
- If you have recurring UTIs, ask your doctor for a standing order for a UTI test at a laboratory near you. Then simply let your doctor know each time you drop off a sample.
- You should use a cup provided by your physician to collect a sample (follow the recommendations above) and should store it in a fridge if it’s going to take you more than an hour to drop it off.
- If you’ve had a lot of “negative urine samples,” ask if your urine can be cultured for more than the standard 48 hours. A little-known fact: you can ask to have your urine kept for up to seven days, which is more likely to show a rare UTI causing bacteria.
- If you’ve had a lot of symptoms, ask your doctor to take seriously any bacteria that show up in your sample. When two or more bacteria are found, they are often labeled as “contamination” because the standard thinking is a single type of bacteria causes a UTI. However, if you have symptoms, several bacteria may be working together to cause your urine infection.
- Some women get UTIs with “less” bacteria than doctors consider significant. Normally, UTI is diagnosed with at least 100, 000 colony forming units (CFU) per milliliter of bacteria. However, if you have symptoms, fewer bacteria could be causing your symptoms (Schaeffer, 2010). Ask your doctor if any bacteria grew, even if it is a small amount.
With a little know-how, you can make sure you are getting the right diagnosis. Have you tried an over-the-counter UTI test kit? What was your experience?
- Fihn SD. Clinical practice. Acute uncomplicated urinary tract infection in women. N Engl J Med 2003;349:259–66.
- Kass EH. Asymptomatic infections of the urinary tract. Trans Assoc Am Phys 1956; 69:56-63.
- Pezzlo M. Detection of urinary tract infections by rapid methods. Clin Microbiol Rev 1988;1:268–80.
- Pfaller M, Koontz F. Laboratory evaluation of leukocyte esterase and nitrite tests for the detection of bacteriuria. J. Clin. Microbiol. May 1985; 21(5): 840-842.
- Recurrent uncomplicated cystitis in women: allowing patients to self-initiate antibiotic therapy. Prescrire Int. 2014 Feb;23(146):47-9.
- Ruf M, Morgan D, Mackenzie K. Differences between screening and diagnostic tests and case findings. Retrieved at: https://www.healthknowledge.org.uk/public-health-textbook/disease-causation-diagnostic/2c-diagnosis-screening/screening-diagnostic-case-finding
- Sanford JP, Favour CB, Mao FH, et al. Evaluation of the positive urine culture; an approach to the differentiation of significant bacteria from contaminants. Am J Med 1956;20:88–93.
- Schaeffer A, Matulewicz R, Klumpp D. Infections of the Urinary Tract. In Wein A, Kavoussi L, Partin A, Peters C (Ed.) Campbell- Walsh Urology (10th ed). Philadelphia, PA: W.B. Saunders, 2011
- Semeniuk H, Church D. Evaluation of the leukocyte esterase and nitrite urine dipstick screening tests for detection of bacteriuria in women with suspected uncomplicated urinary tract infections. J Clin Microbiol 1999; 37:3051–2.
- Simerville J, Maxted W, Pahira J. Urinalysis: a comprehensive review. Am Fam Physician. 2005 Mar 15;71(6):1153-62.
- Taneja N, Chatterjee S, Singh M et al. Validity of quantitative unspun urine microscopy, dipstick test leucocyte esterase and nitrite tests in rapidly diagnosing urinary tract infections. J Assoc Physicians India. 2010 Aug;58:485-7.