How do you interpret a sensitivity report from a urinalysis (UA)?

From the Guidelines

To interpret a sensitivity report from a urinalysis (UA), it is crucial to understand that the report's sensitivity is around 64% and specificity is around 91%, as indicated by a study published in the Annals of Emergency Medicine 1. When reading the report, first identify the organism(s) cultured from the urine sample. Next, examine the antibiotic susceptibility results, which are usually presented in a table format with antibiotics listed vertically and their effectiveness marked as "S" (sensitive), "I" (intermediate), or "R" (resistant).

Key Considerations

• Focus on the "S" antibiotics as these will be most effective against the identified pathogen.
• Consider factors like antibiotic spectrum (narrow is preferred when possible), side effect profile, cost, and patient-specific factors such as allergies or kidney function when selecting treatment.
• For uncomplicated urinary tract infections, common first-line antibiotics include nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin, typically for 3-5 days in women and 7-14 days in men, as suggested by guidelines 1.

Interpreting Results

• A positive urinalysis result is defined by the presence of pyuria (≥5 WBCs/hpf), positive leukocyte esterase result, or positive nitrite result 1.
• The sensitivity report is crucial because it helps avoid antibiotic resistance by ensuring the selected medication will effectively target the specific bacteria causing the infection, rather than using broad-spectrum antibiotics unnecessarily.
• It's also important to note that urine contamination rates vary by collection method, with clean catch urine having a higher contamination rate (26%) compared to catheter specimen urine (12%) or suprapubic aspiration (1%) 1.

Clinical Decision Making

• The most critical step is to select an antibiotic that the organism is sensitive to, based on the report, to ensure effective treatment and minimize the risk of antibiotic resistance.
• Consider the patient's clinical presentation, medical history, and potential allergies when choosing an antibiotic.
• Always follow local antibiotic resistance patterns and guidelines, such as those suggested by the American Academy of Pediatrics 1, to ensure the best possible outcome for the patient.

From the FDA Drug Label

The recommended quantitative disc susceptibility method may be used for estimating the susceptibility of bacteria to sulfamethoxazole and trimethoprim. 3,4 With this procedure, a report from the laboratory of “Susceptible to trimethoprim and sulfamethoxazole” indicates that the infection is likely to respond to therapy with this product. If the infection is confined to the urine, a report of “Intermediate susceptibility to trimethoprim and sulfamethoxazole” also indicates that the infection is likely to respond A report of “Resistant to trimethoprim and sulfamethoxazole” indicates that the infection is unlikely to respond to therapy with this product.

To interpret a sensitivity report from a urinalysis (UA), the following key points should be considered:

• A report of “Susceptible” indicates that the infection is likely to respond to therapy with trimethoprim and sulfamethoxazole.
• A report of “Intermediate susceptibility” for a urinary infection also indicates that the infection is likely to respond to therapy with this product.
• A report of “Resistant” indicates that the infection is unlikely to respond to therapy with trimethoprim and sulfamethoxazole 2.

From the Research

Interpreting a Sensitivity Report from a Urinalysis (UA)

To interpret a sensitivity report from a urinalysis (UA), it is essential to understand the results in the context of the patient's symptoms, medical history, and the antibiotics used to treat urinary tract infections (UTIs) 3, 4.

• Understanding the Report: The report typically includes the type of bacteria causing the infection, the antibiotics tested, and the susceptibility of the bacteria to each antibiotic 5, 6.
• Antibiotic Susceptibility: The report indicates whether the bacteria are susceptible, intermediate, or resistant to each antibiotic tested 5.
• Choosing the Right Antibiotic: The choice of antibiotic should be based on the susceptibility pattern of the bacteria, as well as the patient's medical history, allergies, and other factors 3, 4.
• Limitations of Rapid Diagnostic Testing: While rapid diagnostic testing can provide quick results, it may not always be accurate, and urine culture and sensitivity (C&S) remains the gold standard diagnostic for UTIs 7.
• Clinical Considerations: Clinicians should consider the local epidemiology of antibiotic resistance, the patient's symptoms, and medical history when interpreting the sensitivity report and choosing an antibiotic 3, 6.
• Importance of Local Antibiotic Resistance Patterns: Knowledge of local antibiotic resistance patterns is crucial in guiding empirical therapy for UTIs 3, 5.

Key Points to Consider

• The sensitivity report should be interpreted in the context of the patient's symptoms, medical history, and local antibiotic resistance patterns.
• The choice of antibiotic should be based on the susceptibility pattern of the bacteria, as well as the patient's medical history, allergies, and other factors.
• Urine culture and sensitivity (C&S) remains the gold standard diagnostic for UTIs, and rapid diagnostic testing should be used in conjunction with C&S results.