Urinalysis vs Dipstick (vs culture)

 

 

 

 

Urinalysis

  • A Urinalysis consists of 3 components:
    • Macroscopic (color, clarity, specific gravity)
    • Reagent Strip (chemical analysis)
    • Microscopic
  • There is often variation in providers working regarding which method should be used to evaluate a patient for a urinary tract infection. This will not end the variation (variation is the spice of life)… but let’s illuminate the options:
    • Dipstick Reagent Strip
      • Made of an inert plastic with the separate reagent squares placed upon it.
      • Able to generate results for the 2nd component of urinalysis (not other 2).
      • Pro – it is fast (relatively speaking).
      • Con – it has a large human factor. Timing is critical and an individual’s perception and the ambient light play important roles in the interpretation of the results.
    • IRIS Automated urinalysis system (what our lab uses)
      • Like a full manual urinalysis, it covers the 3 components of urinalysis.
      • Timing and lighting are automatically accounted.
      • Software allows it to perform the microscopic analysis.
      • Very good at identifying negative samples and often will auto-report the results. Abnormal findings will be held for a technologist to review the images and confirm classification.
      • Pro – faster and more economical FOR THE HOSPITAL, when compared to manual urinalysis.
      • Con – takes longer for the provider to get the results (relatively), particularly if abnormal.
  • Where does that leave us? Well, the full urinalysis (whether automated or manual) can have strictly better tests performance measures than the dipstick; however, in the end, it is still an urinalysis and subject to the false negatives. They both need to be considered with appropriate Pre-Test probability assessment.
  • Recently, all of the available literature on whether urine dipstick or the urine microanalysis correlate with positive urine cultures in febrile children was looked at and it was found that the “literature search did not conclusively identify any component of either the urinalysis or the urine microscopy which would allow a practitioner to conclude definitively that the source of that infant’s fever is a UTI.” [1]
    • Well, Jack, that is not helpful!!
  • Here is another tidbit to consider: “Enhanced” urinalysis, using un-spun urine samples, has shown promise at improving the identification of low risk patients for serious bacterial infection… that is nice… but, we don’t have “enhanced” urinalysis available to use.[2]

 

“Educated” opinion:

  • In the 1-3 month old in whom you are interested in performing a Rochester criteria assessment on, you need the Full Urinalysis… send the urine to the lab.
  • In the child in whom your pre-test probability is not low (the child with a prior UTI, known anatomic abnormalities, prolonged fever, etc) then you may benefit from a Full Urinalysis performed in the lab.
  • In the child who has no risk factors and looks great, check the Dipstick. If it equivocal, then send it upstairs.
  • BUT, in all kids who wear diapers, send the CULTURE… because that is where the real answer is.

1. Reference: Perkin J. AAEM Clinical Practice Committee. Clinical Practice Guideline: Does the Urine Dipstick and/or the Urine Microanalysis Correlate with a Culture Positive UTI in Febrile Children? AAEM
2. Herr, S.M., et al., Enhanced urinalysis improves identification of febrile infants ages 60 days and younger at low risk for serious bacterial illness. Pediatrics, 2001. 108(4): p. 866-71.

 

Sean Fox

I enjoy taking care of patients and I finding it endlessly rewarding to help train others to do the same. I trained at the Combined Emergency Medicine and Pediatrics residency program at University of Maryland, where I had the tremendous fortune of learning from world renown educators and clinicians. Now I have the unbelievable honor of working with an unbelievably gifted group of practitioners at Carolinas Medical Center. I strive every day to inspire my residents as much as they inspire me.

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