Urinalysis Part 1: UTI tests

 

 

“DO I HAVE A UTI?”

Ouch, it burns when I pee and I need to go every 5 minutes. I’m a 30-year-old woman.  Do I have a UTI?

That’s an easy one. Yes, there is a very high likelihood that you do. You don’t even really need to check a urinalysis (UA) to tell you so.  In fact, it is so probable that it is accepted practice for your doctor to call in antibiotics without testing. 

However, most cases are not this obvious and then the UA becomes essential information.

Unlike many other familiar tests, an abnormal UA/UTI test by itself does not make the diagnosis. For example, If you see an x-ray with a broken bone then you have a broken bone.  If your hemoglobin is low then you are anemic.  But abnormal UA results don’t necessarily mean you have a UTI!  Still, with a little reading, you can understand how to interpret the UA for UTI.

The good news is that you only need to consider 4 results on the UA panel to decide if there is a UTI.  These are:

And then you must answer 3 questions,

A) Was the urine test properly collected and not contaminated?  This is based on the SQUAMOUS EPI count. If the count is more than 10/HPF there is some element of contamination.

B) Are the UA tests for UTI abnormal? These are The presence of bacteria, Nitirites or elevated WBC’s (or +LE on a dipstick test)

C) Do I have specific UTI symptoms?  These are burning on urination, the frequent need to urinate small amounts of urine, and flank pain (kidney area) pain WITH A FEVER.

Yes, the bad news is that the test results are only part of the answer. One must also consider the symptoms and the quality of the sample which was tested.   

To reiterate this important concept: For UTI diagnosis one must consider

  • The quality of the sample
  • The test results         
  • The symptoms

After answering  the 3 questions you can decide if you have a UTI as follows:

  • If the answer to A is “NO”  (meaning an improperly collected urine sample) then you can’t trust your test results. Skip the rest and have another test ordered. All bets are off. Do not pass GO!    If “YES” go to the next Question.
  • If the answer to B AND C is “YES” then you have a UTI (abnormal test and specific symptoms). 
  • If the answers to both  B and C are “NO” then you don’t have a UTI
  • If only one of questions B or C is “YES”, and the other is “NO”, then you might have a UTI, it’s not for sure.

Or put more simply: For an uncontaminated/clean urine specimen:

If you have typical symptoms and an abnormal UTI test you probably have a UTI.

If you do not have typical symptoms or an abnormal UTI test you probably don’t have a UTI.

If you have only an abnormal UTI test or only a typical symptom you MIGHT have a UTI.

You may not find the last answer very satisfying. THE TRUTH IS, sometimes the best you can say is that someone might have a UTI.   It then becomes a clinical judgment if someone should or should not be treated with antibiotics for a UTI. The other options are to wait for a culture result or to keep looking for an alternative cause for the symptoms.  Remember, antibiotics are not harmless.

Still confused or want some more details” Read on engaged patients!

Here is some more detail about the tests and answering the 3 questions:

How to answer question A:  Was the urine properly collected?

  • SQUAMOUS EPI cells are a contaminant. The answer is “NO” If the SQUAMOUS EPI count is elevated, higher than 10 cells/HPF. Squamous Epithelial cells come from the mixture of external secretions from the genitalia (vaginal or penile discharge) into the urine specimen. An elevated Squamous EPI result is a marker of poor specimen collection technique. The higher the count the more contamination and the less confident you can be in the other UTI test results. 

How to answer question B:  Are any of the UA tests for infection abnormal?

There are only 3 tests to consider:

  • WBC’s: Either a positive Leukocyte Esterase (LE)  on dipstick or more than 5 WBC’s/HPF on microscopic examination is abnormal.  The higher the count the more confident you can be in the result.  Most UTIs show at least 20 WBC’s/HPF and this can go up to the hundreds. Note that if you only have a dipstick test done you only get the LE test, not a specific WBC count, and no measurement of SQUAMOUS EPI cells.  So a positive LE test can be from contamination during collection. You will not know.
  • BACTERIA: Any bacteria reported on the microscopic exam are abnormal.  Bacteria of course are the cause of a UTI.  Sometimes the lab will report “rare” bacteria. Although abnormal, that result is not very convincing. Consider it a “soft positive.”  The absence of bacteria seen on the full microscopic exam does not exclude a UTI, the test is not perfect.  Unfortunately, there is no measurement of bacteria on the dipstick test. 
  • NITRITES: Abnormal is reported as “PRESENT or POSITIVE” or sometimes its presence is graded as 1+,2+, or 3+.   Note that an abnormal nitrite result is considered stronger evidence for a UTI. However, a significant proportion of UTI cases have NEGATIVE nitrites. This is because only some species of bacteria produce it and it takes time to measurably accumulate in the urine. 

If any of these 3 tests are abnormal (positive) the answer to question B  above is YES.

How to answer question C: Are there typical and specific UTI  symptoms?     These symptoms are:

  1. Burning on urination
  2. The urge to urinate frequently, but only small amounts of urine are produced each time you go. 
  3. Flank (kidney) pain AND a fever. 

If any of the above symptoms are present the answer to question C above is YES

CAVEATS: Note that burning on urination and frequency can also be produced by STDs (which are not strictly speaking what we are considering a UTI) as well as yeast infections and irritation of the urethra (where the urine comes out) or from any other form of local irritation. Still, burning and frequency are fairly specific signs of a UTI when there is no vaginal or penile discharge, itching, or irritation/redness.  Also, be aware that flank pain by itself is not very specific. It is commonly caused by back problems, muscle strain, kidney stones, and can be caused by gall stones and appendicitis. Things to consider in the correct context. So there are many causes of flank pain but those associated with a fever are more likely to be from a UTI.  But if you have a fever with abdominal pain vomiting or any other symptom not listed above you should consult your doctor promptly.

 

Example Case 1)

I’m a 30-year-old female and I’m sexually active with one partner. I feel burning when I urinate, and I have to pee every few minutes, but only a small amount comes out. 

  1. Test Results: 
    • Urine Squamous cells 0-2/HPF (not contaminated)
    • 5-10 WBC/HPF  (elevated/abnormal)
    • negative nitrites  (normal)
    • bacteria present. (not normal)
  2. Interpretation of case 1)  
    • A) Yes, the urine was properly collected, there are only 2 squamous cells/HPF. 
    • B) Yes, at least 1 of the 3 UA tests for UTI (WBC’s, bacteria, nitrites) is abnormal.  In this case the WBC count is elevated.
    • C) Yes you have specific UTI symptoms.
  3. Conclusion: You have an abnormal UTI test and specific symptoms. There is a high probability you have a UTI.  You should be treated with antibiotics.

Example Case 2

I’m a 50-year-old female. I feel burning when I urinate, and I have to pee every few minutes, but only a small amount comes out.

  • Test Results
    • No squamous cells were reported (so not contaminated)
    • Urine WBC’s were  0-3/HPF, this is within the normal range (0-5/HPF)
    • Urine Nitrites were absent, which goes against a UTI
    • Urine Bacteria were not seen (this is a normal result and goes against the UTI diagnosis)
  • Interpretation of scenario 2

A) Yes, it’s a good collection, no squamous cells, continue on 

B) No. none of the 3 UA UTI tests were abnormal.

C) Yes, you have some classic symptoms.  

 

Conclusion: Maybe you have a UTI. The tests are not perfect, there are occasional false-negative test results.   But your symptoms are classic. Nevertheless, it could be something else such as vaginitis from a yeast infection or an STD causing urethral irritation.  You have a few options.  You can take antibiotics and see if the symptoms go away while awaiting a culture result. Or, you can send a urine culture and just wait for the results. You can do tests to look for an STD or vaginitis.

 

Example Case 3)

  • I’m a 20-year-old sexually active female and I’m having pain in my back over my left kidney area (flank). I have no fever, it doesn’t hurt to urinate and I’m not urinating frequently. 
  • test results
    • No squamous cells seen, continue on 
    • No nitrites detected
    • No urine WBC were reported.
    • No bacteria reported

Interpretation of scenario 3

A)Yes, it’s a good collection, no squamous cells, continue on 

B) No, none of the 3 UA UTI tests were abnormal.

C) No. you don’t have any specific UTI symptoms. You have flank pain but that is not specific and without a fever less likely from an infection.

Conclusion: It is doubtful that your symptoms are caused by a UTI. You have no abnormal UTI tests and no specific UTI symptoms. Many things can cause flank area pain. Flank pain is common when a UTI reaches the level of the kidneys. But without a fever, it is not very specific for infection.   Low back pain from muscular or skeletal causes is very common, even in the absence of injury. Other potential causes of flank pain include kidney stones, problems in the lower lungs, ovarian cysts, and gallstones can all cause flank pain. In this case, you are lacking both specific UTI symptoms and an abnormal UA.  Think about other causes of flank pain and consider a culture.

Example Case 4

  • I’m a 60-year-old female. I have had lower abdominal pain for a few days. It reminds me of similar pain I experienced about 30 years ago when I had a UTI. I’ve had no fever, no flank pain and no frequency or burning on urination.
  • Test Results
    • 100-200 WBC/HPF: Quite elevated, abnormal. 
    •  negative nitrites.  
    •  positive bacteria:  Abnormal
    • There are also 50-100 Squamous Cells/HPF. 

Interpretation of case 4

A) No. This is a badly contaminated sample with a very high Squamous EPI count and should not be used to determine if there is a UTI. 

B) You can’t interpret the other UTI tests because it is a contaminated sampleNot a classic symptom

C) These are not specific UTI symptoms but it doesn’t matter anyway, you can’t interpret the UA. 

Conclusion 

 Even though the urine WBC’s are quite elevated, and bacteria are seen, these can be from the vaginal secretions. This does not mean that she does not have a UTI, just that the urine can’t be used to aid in that determination. Lower abdominal pain can certainly be caused by a UTI. But it is not a highly specific symptom as many other things can also cause this.   Repeat the urine test. 

Example Case 5

  • Your monther has dementia. For the past few days she seems a little more confused than normal. She has had a mild cough and congestion but no fever. Because of her dementia and incontinance you can’t tell if she is urinating frequently, she has not appeared in pain.
  • Test Results
    • 5-10 Squamous EPI/HPF
    • 30 WBC/HPF
    • Bacteria- MODERATE (a positive result)
    • Nitrites – 1+ (mildly detected on the dipstic reading).

Interpretation of Case 5

A) The specimine quality is adequate and not grossly contaminated

B) All 3 of the UTI tests are abnormal.

C) No specific UTI symptoms although the history reliability is very limited due to dementia.

Conclusion

Your mother MIGHT have a UTI. Often non-specific symptoms are attributed to a UTI in the elderly. In this case her respiratory infection/cold, or many other things could cause similar symptoms So Here is the BIG UA ISSUE IN THE ELDERLY.

Many older elderly individuals always have bacteria growing in the urinary tract which is not causing an infection. Remember, infection implies bacteria growing in the urinary tract which are causing inflammation and therefore symptoms.   The presence of bacteria that are just hanging out and not causing a problem is called “asymptomatic bacteriuria” or “colonization.” Frequently, the elderly also have some WBC’s in the urine, a sign of inflammation. However, with no symptoms, it is still not considered an infection. People who have a foley catheter in place for more than a few weeks will almost always have some WBC’s and bacteria in the urine. Asymptomatic bacteriuria should not be treated with antibiotics. It is not causing harm and will just come back as a more resistant bacteria. 

A note on dipstick only tests

Appreciate the limitations of the dipstick portion of the urinalysis. This may be all you get in urgent care or while you are in a medical office. The full test takes longer and, unless you are in a hospital or more advanced setting, usually needs to be sent out to a lab, so you may not get a result for a few hours.

Urinalysis: How to Interpret Your Results | GMP Medical ...

The dipstick gives a “colorimetric” result. When dipped in urine each test changes color. The color which results is visually inspected or read by a machine and the color (and strength of the color change) correspond with the result. It is “semi-quantitative” in that the color change is an estimate of the urine concentration of whatever you are testing for. False-positive and false-negative tests from interfering substances (medications excreted in the urine), specimen contamination during collection, and improper visual inspection interpretation can occur.

What you do not get with a dipstick is important. You do not get a measurement of bacteria in the urine and you do not get a Squamous EPI count. So you never know if the specimen is properly collected and not contaminated.

With respect to UTI diagnosis the urine dipstick contains the following tests:

Leukocyte Esterase: This is a chemical found on WBC’s and when LE is positive indicates that WBC’s are in the urine. If you have a microscopic result then ignore your dipstick result. The microscopic WBC measurement is more accurate. A contaminated urine specimen will be falsely positive from external secretions containing WBC’s.

Nitrites: This result is only a dipstick test.

What is the urinary tract

The Urinary Tract includes the kidneys, ureters, bladder, and urethra. In most cases, a UTI occurs when bacteria enter the system through the urethra. With increasing severity it moves up to the bladder and then to the kidneys. Your doctor may simply tell you you have a UTI but she could be referring to an infection in any part of the system.

Pyelonephritis: This is a UTI that has reached the kidneys. If you have a fever or flank pain this is probably the case.

Cystitis: This is a UTI that has reached the bladder but is not up to the kidneys. This is common.

Urethritis: In this case, infection is restricted to the lowest portion of the urinary tract, the urethra. Urethritis can occur from typical bacteria normally found on the vagina or skin. But it can also result from exposure to STDs (Chlamydia, Gonorrhea, Trichomonas.), from yeast infections, or from chemical (cosmetics) or “mechanical” irritation.