What are the findings of a Urinalysis (UA)?

From the Guidelines

Urinalysis (UA) is not reliable for diagnosing urinary tract infections (UTIs) and should not be used as the sole basis for diagnosis, as it has limited diagnostic value and a low positive predictive value for infection. The findings of a UA include physical, chemical, and microscopic evaluations designed to aid in diagnosing kidney, metabolic, oncologic, and infectious disorders 1. However, the absence of pyuria can help rule out infection in most patient populations, while the presence of pyuria often indicates genitourinary inflammation due to various noninfectious reasons 1.

When interpreting UA results, clinicians should consider the following:

• The presence of nitrite and leukocyte esterase in the UA can indicate a possible UTI, but their absence does not rule out the infection 1.
• Urine cultures are reasonable for complicated cases and/or recurrent UTIs, particularly in suspected pyelonephritis, to guide targeted therapy 1.
• In simple uncomplicated cystitis in healthy nonpregnant patients, routine cultures are not necessary 1.
• Clinical symptoms, such as changes in urine color or odor, cloudy urine, macroscopically hematuria, nocturia, decreased urinary output, dysuria, suprapubic pain, and urinary retention, should be integrated with UA findings to guide diagnosis and treatment 1.

In clinical practice, evidence-based diagnosis of UTI should be primarily based on clinical symptoms, and UA findings should be used to support or rule out the diagnosis, rather than as the sole basis for diagnosis 1.

From the Research

Urinalysis Findings

The findings of a urinalysis (UA) can be used to diagnose and predict urinary tract infections (UTIs) [ 2, 3,4,5,6 ].

• A positive UA is defined as positive leukocyte esterase, positive nitrite, WBC > 10/high power field, or presence of bacteria [ 2 ].
• The sensitivity, specificity, positive predictive value, and negative predictive value of the UA for UTI were 100%, 65.1%, 15.5%, and 100%, respectively [ 2 ].
• A negative UA reliably excludes a catheter-associated UTI in the febrile, trauma ICU patient with a 100% negative predictive value [ 2 ].

Predictive Performance of Urinalysis

The predictive performance of UA for urine culture results according to the causative microorganisms can be evaluated 3.

• The combination of leukocyte esterase and nitrite tests showed the highest area under the curve (AUROC, 0.766; 95% CI, 0.764-0.768) for predicting urine culture positivity 3.
• The application of an AI model improved the predictive power of the model for urine culture results to an AUROC of 0.872 (0.870-0.875) 3.

Urinalysis to Reflex Culture Process Change

A process change was implemented at a US Department of Veterans Affairs medical center ED that automatically cancelled UCs if UAs had < 5 white blood cells per high-power field (WBC/HPF) 4.

• The UA to reflex culture process change resulted in a significant reduction in processing of inappropriate UCs and unnecessary antibiotic use for ASB 4.
• In patients with negative UA specimens, antibiotic prescribing decreased by 25.3% postintervention 4.

Evaluation of BacterioScan 216Dx

BacterioScan 216Dx is an FDA-cleared semiautomated system to detect bacterial growth in urine 5.

• The sensitivity and specificity of 216Dx versus UA were 92.1% versus 97.3%, 82.7% versus 63.8%, respectively 5.
• The 216Dx can be used as an alternative/adjunct screening tool to UA to rule out urinary tract infection (UTI) in children 5.

Urinary Nitrites or Other Urinalysis Findings

Urinary nitrites or other urinalysis findings cannot be used as a predictor of bacterial resistance of uncomplicated urinary tract infections 6.

• No significant correlation was found between leukoesterase and the resistance patterns in all of the studied antibiotics, except cefazolin 6.
• The use of nitrofurantoin or cephalexin for the treatment of cystitis was optimum, and in the presence of negative leukoesterase, nitrofurantoin was preferable to cephalexin 6.