Continuing our series on scenarios commonly mishandled in primary care, Dr Anish Kotecha explains why dipstick tests in people over 65 should not be used to confirm urinary tract infection (UTI)
You receive a report from the care home. A 70-year-old woman has seemed ‘a bit off colour’ for a few days. She has no urinary symptoms but care home staff have dipped her urine and tell you ‘it shows a water infection’.
The reality
UTIs are common in older women but urine dipsticks are not helpful in over-65s, as a significant proportion will have asymptomatic bacteriuria.1
The issue
In the above scenario, it is all too easy for the care home’s explanation to be accepted and for the GP to write a prescription for antibiotics.
However, there are many other potential illnesses that might be causing non-specific illness or delirium. If we assume it is a UTI, we are unlikely to screen for other possible causes such as pain, other common infections, lack of hydration, constipation and medications, to name a few – with potentially serious consequences.
The other problem is that by prescribing antibiotics unnecessarily we increase the potential for antibiotic resistance.
The evidence
Asymptomatic bacteriuria is thought to occur in up to 20% of healthy elderly women, increasing to up to 50% in those in long-term care.1
Most elderly people with a urinary catheter have bacteria in the bladder or urine without an infection. Urine dipsticks become more unreliable with increasing age over 65 years.
Asymptomatic bacteriuria is not harmful. It can cause a urine dipstick to show a positive result, but the evidence suggests that antibiotics in these cases are not beneficial and may cause harm.2
Avoiding a clanger
Each patient should be fully assessed by taking a complete, focused history and asking specifically about urinary symptoms such as dysuria, urination frequency and nocturia, and changes in appearance of urine and odour.
In the elderly population, patients can also present with non-specific signs of infection like delirium or debility. Red-flag symptoms include a temperature or rigors, haematuria, loin pain, nausea and vomiting. It is helpful to ask how the patient is generally feeling in themselves.
Examination should include a full set of observations. If there is suspicion of a UTI, remember a dipstick test will not help – and, if it is positive, it may stop you investigating other potential causes. Instead, a midstream urine sample should be sent for culture.
If this is negative for an infection, another cause for the patient’s symptoms can then be considered. For genitourinary symptoms this includes thrush, vaginal atrophy, urethritis or prostatitis.
If a patient is catheterised, consider changing it. If symptoms are mild in a patient without a catheter and there is a low risk of complications, a delayed prescription of antibiotics might be considered. If symptoms are moderate to severe or there is a higher risk of complications, an immediate antibiotic prescription may be appropriate.
The urine culture should be chased as soon as possible to review whether antibiotics are indicated or need to be changed.
Narrow-spectrum antibiotics should be chosen where possible and ideally a urine sample should be sent before starting antibiotics (because of the incidence of antibiotic resistance in the elderly population).
If patients are unwell, referral into secondary care for further tests may be considered.
Caveats
Urine dipstick tests may in some cases be reasonable. For example, if patients have recurrent UTIs, a urine dipstick may pick up evidence of haematuria. This could lead to a differential diagnosis of renal stones or even a urological tumour.
Dr Anish Kotecha is a GP partner and trainer in Cwmbran, Wales
Key points
- Urinary tract infections are common in the elderly, but asymptomatic bacteriuria is also very common
- Urine dipsticks are not helpful in people over the age of 65 years
- We should keep an open mind when assessing the elderly and consider all differential diagnoses
Dr Anish Kotecha is a GP partner and trainer in Cwmbran, Wales
References
NICE. CKS: Urinary tract infection (lower) – women. September 2022
Public Health England. Diagnosis of urinary tract infections. May 2020
READERS' COMMENTS [3]
Please note, only GPs are permitted to add comments to articles
Thanks for this. But slightly confused in opening paragraphs.
Our dipsticks test for Leucocyte (esterase) and Nitrite amongst other things.
With asymptomatic bacteriuria, you would expect to have no leucoocytes and usually no nitrite either -i.e .dip negative
With pyuria, you will have leucocytes. MC&S may show bacteria (i.e. UTI) or be sterile (sterile pyuria).
Nitrite is positive with some gram negative UTIs like proteus ,but clinically rare with coliforms.
Perhaps the message should be only treat after considering whole clinical picture, including dip results and MC&S results.
Just an issue with the comment of Dr Greenway.
In fact, all coliforms (Enterobacteriales) produce nitrites – it’s a cardinal definition of the order. Furthermore, not all uropathogenic organisms are nitrite-producing – Pseudomonads, S. saprophyticus, for example.
Dr CP Eades MSc MRCP FRCPath
Regional ID Unit
North Manchester General Hospital
Broadly agree with a few caveats
– A negative dip is still a negative dip so still a potentially useful test.
– Male patients? The headline says “people over 65” but a positive dip probably signficant in a male patient.
– A strongly positive dip is also more likely to mean something at any age -the lab MC+S that’s more misleading??
– 65 is not the same as 85 but similar to 64. Do we abandon testing on their birthday because of a guideline?
Agree that the tests need interpretation.
Its what we trained for.