What is a Urinalysis with reflex to culture?

From the Guidelines

Urinalysis with reflex to culture is a diagnostic approach where an initial urinalysis is performed, and if it indicates a possible infection, a urine culture is automatically conducted without needing a separate order, as recommended by the most recent guidelines 1. This approach is crucial for efficiently diagnosing and treating urinary tract infections (UTIs) while minimizing unnecessary tests and healthcare costs. The process starts with a standard urinalysis, examining the physical, chemical, and microscopic properties of urine to identify abnormalities such as protein, blood, white blood cells, bacteria, or other substances that might indicate infection or disease.

Key Components of Urinalysis with Reflex Culture

• The initial urinalysis screens for signs of infection, including elevated white blood cells, nitrites, or bacteria.
• If the urinalysis results suggest an infection, the laboratory proceeds to a urine culture to identify the specific organism causing the infection and determine the most effective antibiotics for treatment, as outlined in the European Association of Urology guidelines 1.
• This reflex testing approach is particularly useful in cases where the diagnosis is unclear or in patients presenting with atypical symptoms, as it streamlines the diagnostic process and ensures that appropriate treatment is initiated promptly.

Recommendations for Urine Culture

• A urine culture is recommended in specific situations, such as suspected acute pyelonephritis, symptoms that do not resolve or recur after treatment, women presenting with atypical symptoms, and pregnant women, according to the guidelines 1.
• For patients with mild to moderate symptoms, symptomatic therapy may be considered as an alternative to antimicrobial treatment, with the choice of antimicrobial therapy guided by factors such as the spectrum and susceptibility patterns of the pathogens, efficacy, tolerability, and costs.

Importance of Appropriate Urine Specimen Collection

• Proper collection of urine specimens is critical for accurate diagnosis, with methods including mid-stream or clean-catch specimens for cooperative and functionally capable elderly men, and in-and-out catheterization for women, as recommended by the Infectious Diseases Society of America 1.
• For residents with long-term indwelling urethral catheters, catheter change prior to specimen collection and institution of antibiotic therapy is advised if urosepsis is suspected, to ensure accurate diagnosis and effective treatment.

By following the guidelines for urinalysis with reflex to culture, healthcare providers can optimize the diagnosis and treatment of urinary tract infections, improving patient outcomes and reducing the risk of complications, as supported by the most recent and highest quality evidence 1.

From the Research

Definition of Urinalysis with Reflex to Culture

• Urinalysis with reflex to culture (URTC) is a diagnostic aid for urinary tract infections (UTIs) that employs a set of criteria to determine whether a urine analysis (UA) will reflex to a culture 2.
• The criteria utilized to determine whether a UA will reflex varies due to a lack of evidence-based guidance 3, 2.

Purpose of Urinalysis with Reflex to Culture

• The purpose of URTC is to predict culture positivity and determine the extent to which it predicts culture positivity 2.
• URTC is used to limit laboratory workload by not performing culture on negative specimens and to improve antimicrobial stewardship by not giving antimicrobials to patients with negative UA results 4.

Criteria for Urinalysis with Reflex to Culture

• The URTC criteria may include moderate or more white blood cells (> 5 high-power field [HPF]), few or more bacteria (> 1 HPF), and few or no epithelial cells (< 3 HPF) 2.
• Other criteria may include positive leukocyte esterase, positive nitrites, or white blood cells (WBC) > 10 cells 5.

Impact of Urinalysis with Reflex to Culture

• URTC can reduce the number of urine cultures performed, leading to more accurate diagnoses of catheter-associated UTIs (CAUTI) 6.
• Restrictive UARC criteria can prevent unnecessary urine cultures and reduce the treatment of asymptomatic bacteriuria (ASB) 5.
• The positive predictive value (PPV) of URTC varies across studies, with one study showing a PPV of 58% 2.