What is the evidence for performing a urinalysis for Urinary Tract Infection (UTI)?

From the Guidelines

Urinalysis is a crucial diagnostic tool for urinary tract infections (UTIs) and should be performed to detect key markers of infection, including leukocyte esterase, nitrites, and microscopic examination for bacteria and white blood cells, as recommended by the most recent guidelines 1. When evaluating a suspected UTI, a urinalysis should be performed to rapidly identify infection markers, allowing for prompt treatment initiation while awaiting culture confirmation. The presence of these markers, particularly in combination, provides good evidence of infection.

Key Points to Consider

• The European Association of Urology guidelines emphasize the importance of a thorough medical history and physical examination for patients with urological infections, including UTIs 1.
• Urinalysis results can guide appropriate antibiotic therapy before urine culture results are available, typically in 48-72 hours.
• A urine culture remains the gold standard for definitive diagnosis, identifying the specific pathogen and its antibiotic sensitivities, which is particularly important for complicated UTIs, recurrent infections, or when empiric therapy fails.
• The evidence supporting urinalysis is based on its ability to rapidly identify infection markers, allowing for prompt treatment initiation, thereby reducing symptom duration and preventing potential complications like pyelonephritis.

Recommendations for Urinalysis

• Urinalysis should be performed on all patients with suspected UTI to detect key markers of infection 1.
• The minimum laboratory evaluation for suspected UTI should include urinalysis for determination of leukocyte esterase and nitrite level by use of a dipstick and a microscopic examination for WBCs 1.
• If pyuria (≥10 WBCs/high-power field or a positive leukocyte esterase or nitrite test is present on dipstick, only then should a urine culture (with antimicrobial susceptibility testing) be ordered 1.

From the Research

Urinalysis for Urinary Tract Infection (UTI)

• Urinalysis is a valuable tool in the initial evaluation of dysuria, a common presenting complaint of women 2, 3, 4, 5
• The most diagnostic symptoms of UTI include change in frequency, dysuria, urgency, and presence or absence of vaginal discharge 2
• Dipstick urinalysis is popular for its availability and usefulness, but results must be interpreted in context of the patient's pretest probability based on symptoms and characteristics 2
• Nitrites are likely more sensitive and specific than other dipstick components for UTI, particularly in the elderly 2
• Microscopic urinalysis is likely comparable to dipstick urinalysis as a screening test 2, 6
• Bacteriuria is more specific and sensitive than pyuria for detecting UTI, even in older women and during pregnancy 2
• Pyuria is commonly found in the absence of infection, particularly in older adults with lower urinary tract symptoms such as incontinence 2

Sensitivity and Specificity of Urinalysis

• Urine dipstick has an overall sensitivity of 0.79, specificity of 0.39, positive predictive value (PPV) of 0.30, and negative predictive value (NPV) of 0.85 6
• Urinalysis exhibits a high sensitivity of 0.95 and a poor specificity of 0.21 6
• Urine culture is the gold standard for detection of UTI 2, 3, 5

Clinical Decision Rules

• Clinical decision rules may increase the accuracy of diagnosis with and without laboratory analysis 3
• Evaluation and treatment of dysuria through a virtual encounter without laboratory testing may increase recurrent symptoms and antibiotic courses 3
• Persistent symptoms after initial evaluation and treatment require further workup for infectious and noninfectious causes 3, 4