From the Guidelines
For a 75-year-old woman with persistent pyuria, the next best test is a urine culture to identify the specific causative organism, as recommended by the Infectious Diseases Society of America guidelines 1. This should be performed before initiating antibiotic therapy to ensure appropriate treatment. The urine sample should be collected as a clean-catch midstream specimen to minimize contamination. If the patient has recurrent or complicated urinary tract infections, additional testing may include renal ultrasound to evaluate for structural abnormalities, post-void residual measurement to assess for incomplete bladder emptying, and possibly cystoscopy if there are concerns for underlying pathology such as stones or malignancy. Persistent pyuria in elderly women is often due to bacterial urinary tract infections, but can also result from non-infectious causes like interstitial cystitis or genitourinary tuberculosis. Age-related changes in the urogenital tract, including decreased estrogen levels leading to vaginal atrophy, altered immune function, and increased prevalence of comorbidities like diabetes, contribute to the higher risk of persistent pyuria in this population. According to the ACR Appropriateness Criteria for recurrent lower urinary tract infections in females 1, imaging is of low yield in patients without underlying risk factors, with less than two episodes per year on average, and who respond promptly to appropriate therapy. However, in patients with bacterial persistence or recurrent infections, imaging studies such as renal ultrasound may be indicated to detect a treatable condition and monitor its progress. It is essential to note that pyuria accompanying asymptomatic bacteriuria is not an indication for antimicrobial treatment, as stated in the Infectious Diseases Society of America guidelines 1. Therefore, a urine culture is the most appropriate next step in managing this patient's condition.
From the Research
Next Best Test for Persistent Pyuria
In a 75-year-old woman with persistent pyuria, the next best test to consider would be:
- Urine culture, as it is the gold standard for detection of urinary tract infection 2
- Microscopic urinalysis, which is likely comparable to dipstick urinalysis as a screening test 2
- Automated urinalysis, which provides more sensitive detection of leukocytes and bacteria in the urine 3
Considerations for Pyuria Cutoffs
When interpreting pyuria results, it's essential to consider the cutoff values, as current pyuria cutoffs may be too low and promote inappropriate UTI diagnosis in older women 4. A cutoff of 264 leukocytes/µL may be more specific and sensitive for UTI diagnosis in older women 4.
Importance of Clinical Context
The diagnosis of UTI should take into account the patient's symptoms, clinical context, and risk factors, as pyuria can be present in the absence of infection, particularly in older adults with lower urinary tract symptoms 2, 4.
Additional Testing
In cases where the probability of UTI is moderate or unclear, additional testing, such as urine culture, should be performed to confirm the diagnosis 2.
Limitations of Pyuria Screening
Pyuria screening has limitations, including low specificity and positive predictive values, particularly in patients with underlying conditions, such as those on long-term hemodialysis 5. Therefore, samples with positive pyuria should be cultured to confirm UTI.