Should we test RSV-positive infants for UTIs?

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RSV-positive bronchiolitis in infants is one of the most common reasons for admission to hospital. Sometimes they spike temperatures. It is widely recognised that the rate of serious bacterial infection in these infants is low. But what about the rate of UTIs? Should we be doing urine dips on all febrile babies with bronchiolitis, or is that overkill?

This study hypothesised that UTIs in 3-12 month old febrile, RSV-positive infants are rare.

Kaluarachchi D, Kaldas V, Erickson E, Nunez R, Mendez M., When to perform urine cultures in respiratory syncytial virus-positive febrile older infants? Pediatr Emerg Care. 2014 Sep;30(9):598-601. 

Who was studied?

This was a retrospective study of all infants (0-12 months) admitted to a US paediatric unit between 2006 and 2012.

Inclusion criteria were:

  • febrile infants
  • admitted as an inpatient
  • positive for rapid RSV antigen detection test or NPA

Exclusion criteria were:

  • born before 36 weeks
  • known urinary tract abnormalities
  • previous UTIs
  • known immunodeficiencies
  • already give antibiotics 72 hours prior to urine sample

All patients had urinalysis and urine culture obtained by catheterisation.

412 patients were included (57% boys, 43% girls).

What were the outcomes measured?

Patients were retrospectively examined for a positive urinalysis (leukocyte +/- nitrite or 5+ WCC on microscopy).

They were also assessed for presence of UTI (growth of a single identified pathogen).

Other measured outcomes were: age, sex, race, circumcision status, maximum temp, WCC, and neutrophil count.

What did the results show?

Out of 414 infants, 6.3% had a positive urine culture.

The most common pathogen was E. coli.

Sex, race, age, peak temp, WCC or neutrophil count were not associated with an increased risk of UTI.

In infants aged 3-6 months, 7.7% had a concurrent UTI.

Circumcised boys had a reduced risk of UTI.

RSV positive bronchiolitis is very common. When these infants become febrile, we should not be discounting a concurrent UTI. 6.3% of infants do have a UTI as well as their bronchiolitis. Don’t assume the temp is due to bronchiolitis – check the urine.

 

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About 

Tessa Davis is a paediatric emergency registrar from Glasgow and Sydney, but currently living in London. Tessa tries to spend time with her 3 kids in between shifts. @tessardavis | + Tessa Davis | Tessa's DFTB posts

5 Responses to "Should we test RSV-positive infants for UTIs?"

  1. Kaitlin
    Kaitlin 2 years ago .Reply

    I would question that just because a bacteria can be grown does this mean that we should treat it. I wonder how many well infants if we culture their urine would grow something and thus have asymptomatic bacteriuria? Thus even if we find UTIs should we treat them?

    • Tessa Davis
      Tessa Davis 2 years ago .Reply

      Very true – and as Fenton O’Leary has pointed out on twitter – we also don’t know the significance of the RSV positive result. These weren’t patients who were necessarily symptomatic for bronchiolitis, so the RSV result may equally be a red herring.

  2. Peter Snelling
    Peter Snelling 2 years ago .Reply

    Thanks Tessa for highlighting this issue.

    I agree that it is important to not have ‘the blinkers on’ when it comes to febrile infants with a concurrent respiratory illness, and I have certainly detected other focuses including UTIs. The main limitations with this article is that it was a retrospective study with all urine collections via sterile catheter, where there is evidence for higher rates of contamination in uncircumcised infants, even with skin cleansing. The flip side is over-investigating children, leading to false positives and more invasive investigations and unnecessary treatments.

    Cheers,
    Peter

    [Risk Factors for Contamination of Catheterized Urine Specimens in Febrile Children, Pediatric Emergency Care: January 2011 – Volume 27 – Issue 1 – pp 1-4 doi: 10.1097/PEC.0b013e3182037c20]

    • Tessa Davis
      Tessa Davis 2 years ago .Reply

      Interesting – thanks Peter. I wasn’t aware that there was a higher risk of contamination for catheter specimens in uncircumcised infants. I’ll check out that article.

  3. Dinushan Kaluarachchi
    Dinushan Kaluarachchi 2 years ago .Reply

    I agree with both Kaitlin and Peter. We had the same thought process when we did the study. Our hypothesis was that, UTIs are rare in this population (febrile older infants) and routine urine cultures are not needed. But on this study we found a 6.1% UTI rate.
    In 2011, American Academy of Pediatrics (AAP) changed their UTI diagnosis criteria. According to the new AAP definition you need to have a positive urinalysis and urine culture with >50 000cfu to diagnose a UTI. We published our second paper (see the link below) comparing UTI rates using old and new AAP UTI definitions. Once we apply the new definition the rate of UTI was only 1.1%. As the new AAP guidelines suggest if you don’t have pyuria, the positive culture is just a representation of contamination or asymptomatic bactiuria. So the UTI rate of 6% in the initial study could be a mere representation of contamination or asymptomatic bactiuria.
    In my opinion, I don’t think RSV positive febrile patients are at increased risk of UTIs, because there is no valid biological explanation to it. But you should use your clinical judgement to test for UTIs depending on clinical circumstances.

    Thanks
    Dinushan

    http://cpj.sagepub.com/content/53/8/742.short
    PMID: 24681546

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