Recently, I was asked about the reliability of urine test strips in identifying UTIs. Here, you’ll find my response to the question along with some useful information from other sources regarding the reliability of dipsticks as a diagnostic tool in an aged care setting.
Thank you, Megan, for asking the question “do dipsticks reliably identify or exclude urinary tract infections in elderly people?” The question was related to residential care and older adults generally.
Mmmmm, in attempting to locate a yes or no answer in the literature, I have surpassed my 20 CPD hours for this year. Thank you! My reading has been interesting but the ‘answer’ to the question may be unsettling for some nurses.
As best as is possible, this discussion is strictly limited to the efficacy or otherwise of dipsticks readings for nitrites and leukocyte esterase as a diagnostic tool for urinary tract infections in elderly people. It is not a general discussion on urinary tract infections or antibiotic use.
Nitrites
Nitrites are associated with gram negative bacteria, which converts nitrates to nitrites, after a period of at least three (3) hours in the bladder. Nicolle, 1997 indicated that 50% to 60% of urinary tract infections in residential aged care were due to gram negative bacteria, Escherichia coli the most common. Not all are due to gram negative bacteria, therefore nitrates may not be converted to nitrites.
Leukocyte esterase
This is an enzyme found in most white blood cells, a high count may indicate an inflammatory condition of the urinary tract system.
The ‘go-to’ assessment activity
From my observations, dipsticks are certainly the ‘go-to’ assessment activity in most residential aged care facilities, as well as other health care settings
You will often overhear all levels of staff ‘diagnosing’ urinary tract infections because an older person has become “confused” or “more confused”. The dipstick is then employed, very often without any other assessment.
No gold standard exists
A Delphi procedure consensus indicates that because there is no gold standard to differentiate between asymptomatic bacteriuria and a urinary tract infection, urinalysis and or cultures, alone should not determine treatment unless both nitrite and leukocyte esterase are negative. (van Buul et all. 2019).
Australian authors Godbole, et al. (2020), state a dipstick that reads negative for both nitrite and leukocyte esterase is more reliable at excluding a urinary tract infection whereas, a positive reading for both nitrite and leukocyte esterase has a low positive predictive value, that is, there is a greater chance the person does not have a urinary tract infection.
Juthani-Metha et al. (2014), stated that because of low positive predictive value, even if both nitrite and leukocyte esterase are positive, it is not helpful in evaluating a urinary tract infection in an older person.
The dipstick has its limitations
Burkett et al (2019), state that the dipstick alone must never be relied upon as a standalone diagnostic tool for a urinary tract infection, even if negative for nitrites and leukocyte esterase.
A paper by Al-makdase et al (2020) emanating from the 2019 British Geriatrics Society Autumn meeting, states that “urine dipsticks and urine cultures are no longer diagnostic tools”, due to the prevalence of asymptomatic bacteriuria in the elderly.
Public Health England (2018), states that dipsticks are not to be used in primary care in those over 65 years of age, as they are unreliable in the elderly. According to Rousham et al (2019), this has not stopped some health professionals ?
In a study of older adults admitted to hospital for bacteremic urinary tract infections (Shimoni, et al. 2017), it states that the dipstick was sensitive (96.9%) but with a false positive of 42.4% in patients with a negative culture result.
Finally, in their systematic review of the literature relating specifically to aged care homes and services Eriksen, & Bing-Jonsson, 2017 concluded that although the dipstick is not reliable, there is no alternative at the moment. They recommend that nurses not only understand the limitations of dipsticks but understand the correct method of sample collection, how the dipstick should be used, and how to correctly interpret the results.
This brings me to a final comment. From my readings, the urine being tested in all the studies was a:
- a clean catch or
- a catheter specimen.
It was also assumed that health professions had knowledge of the accepted criteria for a urinary tract infection as distinct from asymptomatic bacteriuria (another blog), in the elderly.
The development of a change in cognition as a standalone symptom is not diagnostic of a urinary tract infection although it is a symptom of a change in health status.
While waiting for that clean catch (yet another blog)!
Commence documenting the details of the comprehensive nursing assessment that was completed to identify other possible causes for the change in an older person’s physical/mental state.
Megan, from my readings it would seem that although a urinary dipstick showing the presence of nitrites and leukocyte esterase, in an older person does not necessarily mean they have a urinary tract infection.
Oh, by the way, ‘more confused’ is not an accurate or objective measurement of cognition ?
Disclaimer
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