Urinary calprotectin as a diagnostic tool for detecting significant bacteriuria

Area of Science:

• Urology
• Infectious Diseases
• Biochemistry

Background:

• Urinary tract infections (UTI) are commonly screened using dipstick pyuria, but its absence does not rule out UTI.
• Urinary calprotectin, an innate immune mediator released by leukocytes, is a potential biomarker for UTI.
• Leukocyte presence significantly elevates urinary calprotectin, suggesting it might be more sensitive than dipstick pyuria.

Purpose of the Study:

• To evaluate the diagnostic value of urinary calprotectin for UTI detection.
• To compare the sensitivity of urinary calprotectin against dipstick pyuria in identifying UTI.

Main Methods:

• Prospective study of 162 patients undergoing urine dipstick, urine culture, proteinuria quantification, and urinary calprotectin determination via ELISA.
• UTI defined as ≥10^5 CFU/ml of uropathogenic bacteria.
• Exclusion criteria included acute kidney injury, chronic renal insufficiency, and urinary tract tumors.

Main Results:

• 71 patients (43.8%) had UTI. Among those without UTI, 23 had contamination and 19 had asymptomatic bacteriuria.
• Receiver operating characteristic (ROC) analysis showed Area Under the Curve (AUC) of 0.70 for calprotectin and 0.71 for pyuria, with no significant difference (p=0.9).
• Patients with significant bacteriuria but without pyuria showed significantly higher urinary calprotectin levels (544.7 ng/ml) compared to those with neither pyuria nor UTI (95.6 ng/ml, p=0.029).

Conclusions:

• Urinary calprotectin is non-inferior to dipstick pyuria in detecting UTI.
• Calprotectin may serve as a valuable diagnostic marker for UTI, particularly in cases lacking pyuria.
• Further research could explore the integration of urinary calprotectin into UTI diagnostic algorithms.