Comparison of Urinary Red Blood Cell Distribution (URD) and Dysmorphic Red Blood Cells for Detecting Glomerular Hematuria: A Multicenter Study.

Background: The clinical utility of urinary red blood cell (RBC) distribution (URD) remains limited. This study aimed to compare the diagnostic performance of URD and dysmorphic RBC (dRBC) in a multicenter study.

Methods: This study enrolled 703 patients who visited four tertiary medical centers in Korea. Patients were classified into glomerular diseases with biopsy (N = 169), renal diseases including chronic kidney disease (N = 194), nephrotic syndrome (NS; N = 88), tubulointerstitial diseases (N = 36), acute kidney injury (N = 32), others (N = 10), and extrarenal diseases (N = 174). Renal parameters, urine microscopic examination, urinalysis, and URD assessments were conducted. The diagnostic performances of dRBC and URD were evaluated.

Results: Median values of both dRBC and URD were significantly elevated in patients with glomerular diseases. URD exhibited a significant correlation with dRBC (r = 0.536) and albumin creatinine ratio (r = 0.186), while no significant correlation was observed with specific gravity (r = -0.03). Among renal diseases, dRBC and URD values were notably higher in patients with NS. The agreement rate between dRBC and URD results was 78.3% (112/143), with 31 instances showing discrepancies. ROC curve analysis comparing glomerular and extrarenal diseases yielded cutoff values of 18% for dRBC and 31.9% for URD, resulting in corresponding areas under the curve (AUC) of 0.79 and 0.83, respectively.

Conclusions: URD exhibited a comparable diagnostic performance, as indicated by a similar AUC value to that of dRBC, while offering the added advantage of providing objective and standardizable results. This attribute enhances its utility as a parameter for distinguishing between patients with glomerular hematuria (GH) and those with non-GH.