Urine testing; who gets the antibiotics??

Just to let you know, the patent in cubicle 7 has got a UTI, can you prescribe her some antibiotics?

Err, I guess so. How do you know?

Well she just went for a wee, it looks infected and and she’s got leucocytes on her dipstick…..

We’re often led by tests that we haven’t ordered and understanding the context and implications of those tests is a tricky skill to master. Bedside urine testing is probably one of the most frequently performed tests in the ED and a good understanding of it’s application is essential.

Screen Shot 2015-03-02 at 11.33.57 Like all tests in medicine, making sure you apply the test to the right patient is the first important step. Test the wrong person and you’ll be dishing out the inappropriate antibiotics like smarties, miss testing in the right patients and they’ll miss out on an effective treatment.

So what is it that makes you decide to prescribe treatment for a UTI? The utility of the dipstick might surprise you and fortunately there is some useful guidance out there on how to approach a ?UTI.

You also need to remember is that no test is perfect and make sure you’re looking for a UTI in a patient that has a reasonable chance of having one. That might sound obvious but if a test is going to throw up some false positives, it won’t throw up as many in a population with a  reasonable prevalence.

That’s where a really good history and examination come into play. It makes sense that the more symptoms you have of a  UTI the greater your likelihood of have one, without any your looking for that needle….

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The first fundamental is that having bacteria in your urine isn’t necessarily a bad thing. Similarly to normal commensals being present in the gut to help fight infection, bacteria in your urine can do the same. As you get older this becomes more common and may vary anywhere from 0.6-17%. The important part is whether or not these bacteria begin to cause you symptoms, only if they do should it be termed a UTI.

It’s useful to also understand a bit about the properties of urinalysis and what the important indicators are. A systematic review from Medina-Bombardó in 2011 evaluated the utility of urine dipstick testing in women, they found leucocytes to have LR+ 1.4 (1.2-1.6) and LR- of 0.44 (0.35-0.56) and nitrites LR+ 6.5 (4.2-10) and LR- (0.58-0.64). With some useful and some less useful properties of these tests, the application needs to be in the correct patient group, with consideration to where the patient lies with regards to the test threshold.

 SIGN guidelines on UTI

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These offer some great advice on the tricky but important topic so it’s probably worth just running through the key points and they are split up into different categories.

The key symptoms attributable to a lower urinary tract infection are;

  • dysuria
  • frequency of urination
  • suprapubic tenderness
  • urgency
  • polyuria
  • haematuria

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Adult women

Experiencing >2 symptoms or severe symptoms and aged<65 years consider empirical treatment except if vaginal discharge is present, this decreases the likelihood of bacteriuria and should prompt a pelvic exam.

Experiencing ≤ 2 symptoms use the dipstick test to guide management, a negative dipstick reduces likelihood of UTI from 50% to<20%.  However these women may still benefit from treatment symptomatically with an NNT of 4, at this point discuss management with the patient regarding prescriptions vs returning to a health care provider if symptoms not settling/worsening.

Trimethoprim or nitrofurantoin are good first line choices for antibiotic therapy. If this fails then send a urine culture and prescribe against the result.

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Pregnant Women

Approximately 1 in 5 prenancies will have an associated bacteriuria. UTI has been linked to  pre-labour, premature rupture of membranes (PPROM) and pre-term labour

Do not use dipstick testing to screen for UTI in pregnancy, urine culture is the gold standard.

Treat both symptomatic and asymptomatic bacteriuria with antibiotics.

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Adult Men

There is no evidence to suggest the best method of diagnosing a UTI in men and it is not possible to extrapolate from evidence in women. UTI’s in men are viewed as complicated as they result from anatomic or functions anomalies for the urinary tract.

Consider conditions such as prostatitis and GU infections in men presenting with dysuria or frequency.

In all men with symptoms of UTI a urine sample should be taken for culture. 

The Health Protection Agency suggests that a seven day course of trimethoprim or nitrofurantoin may be considered for those with symptoms of uncomplicated lower UTI.

 

 Patients with Catheters

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Between 2 and 7% of patients per day with catheter develop bacteriuria.

The following can be indications of a UTI in a catheterised patient;

  • new costovertebral tenderness
  • flank pain
  • suprapubic discomfort
  • nausea and vomiting
  • malaise
  • confusion
  • rigors
  • new onset delirium
  • fever greater than 37.9°C oror 1.5°C above baseline on two occasions during 12 hours

Catheterised patients should be admitted to hospital if systemic symptoms.

Change long term indwelling catheters before starting antibiotic treatment for symptomatic UTI.

Recommend a seven day course of antibiotic treatment for patients with symptomatic catheter-associated UTI, extended to 10-14 days if slow or no response. If women < 65 years have  the catheter removed then 3 days treatment may suffice.

Change in character of the urine does not indicate a UTI  in catheterised patients.

Do not use microscopy or dipstick testing to diagnose UTI in patients with catheters.

So that’s the advice. I’d imagine we all have a tendency to be guided by the urine dipstick a lot more often than this might recommend, but it’s important to remember the principle that tests need to be applied to the right patient in the right way with right interpretation.

So in summary when considering UTI

UTI is a diagnosis founded upon symptoms and signs – the use of tests can inform management but do not make a significant difference to the diagnosis

Urine dipstick testing is only of use in women with 2 or less symptoms for guiding management

 

Simon L

 

References

Medina-Bombardó, David, and Antoni Jover-Palmer. “Does clinical examination aid in the diagnosis of urinary tract infections in women? A systematic review and meta-analysis.” BMC family practice 12.1 (2011): 111.

http://www.sign.ac.uk/pdf/sign88.pdf

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