Written by Doug Wallace
Spoon Feed
In a multi-hospital retrospective review of over 3,000 patient encounters, common urinalysis (UA) parameters had poor positive predictive value (PPV) in diagnosing urinary tract infection (UTI). Absence of certain parameters (i.e. pyuria and leukocyte esterase) had a high negative predictive value (NPV) for ruling out UTI, but were less reliable in older female patients.
Urinalysis in isolation is inadequate
UAs are often ordered even in patients in which there is little suspicion for urinary tract infection (UTI). Many centers, including my own, utilize reflex urine culture approaches based on UA parameters regardless of patient symptoms. This invariably results in urine cultures being sent on patients without overt symptoms of UTI.
This study sought to compare the performance of UA parameters in predicting UTI (see authors’ definition*). No parameters in isolation had > 95% sensitivity (Sn) for UTI. Low-level pyuria (WBC>5) and trace leukocyte esterase both had the best Sn at > 90%, which decreased with increasing levels of both parameters. Bacteriuria and nitrite had poor Sn. All parameters had generally poor positive predictive value (PPV).
On the negative predictive value (NPV) side, absence of leukocyte esterase and pyuria had a high NPV for UTI but was less reliable in female patients >65 years old.
The authors recommend against reflex urine culture and treatment based on UA parameters alone, and recommend a focus on antibiotic stewardship, citing the risk of antibiotic resistance and adverse effects from overprescribing.
How will this change my practice?
This study is a good reminder that treatment should be based on a combination of history, physical exam, and UA findings. Indiscriminate treatment based on UA results alone likely results in unnecessary antibiotic prescribing, with the potential for significant downstream effects.
*UTI was defined as: ≥100,000 CFU/mL plus genitourinary signs/symptoms or at least 2 of the following: fever, rigors, hypotension, nausea/vomiting, delirium, new urologic obstruction or trauma causing bleeding.
Source
Performance of Urinalysis Parameters in Predicting Urinary Tract Infection: Does One Size Fit all? Clin Infect Dis. 2024 Apr 26:ciae230. doi: 10.1093/cid/ciae230. Epub ahead of print. PMID: 38666412.
