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.