Yaroslavl State Medical University

Background . Red blood cell casts are specific markers of glomerular hematuria but are detected infrequently by routine urine sediment microscopy. Pre-analytical sediment preparation may affect their recovery. Objective . To compare red blood cell cast detection using standard and enhanced urine sediment preparation protocols in patients with dysmorphic hematuria and established glomerular disease. Materials and methods . The paired analysis included 68 morning urine specimens from 68 unique patients (one specimen per patient) with dysmorphic hematuria (>5,000 red blood cells / mL), selected from 82 specimens examined between 2023 and 2026. Two independent aliquots were obtained from the same void. In the standard protocol, 10 mL was centrifuged at 400 g for 5 min and the sediment was resuspended in 0.5 mL. In the enhanced protocol, a separate 20-mL aliquot was centrifuged at 1,790 g for 15 min and resuspended in 0.5 mL. Paired results were compared using the exact McNemar test. Results . The cohort included 40 men (58.8 %) and 28 women (41.2 %); median age was 31.5 [23.0; 41.5] years. Red blood cell casts were detected in 15 / 68 specimens with the standard protocol (22.1 %; 95 % CI, 13.8-33.3 %) and in 40 / 68 with the enhanced protocol (58.8 %; 95 % CI, 47.0-69.7 %). Twenty-five pairs were standard-negative / enhanced-positive, while no discordant pairs occurred in the opposite direction (p < 0.001). The absolute increase was 36.8 percentage points (95 % CI, 25.3-48.2), and the detection rate ratio was 2.67 (95 % CI, 1.79-3.98). Among 53 specimens negative by the standard protocol, the enhanced protocol additionally detected casts in 25 (47.2 %). Conclusions . Increasing the initial aliquot volume, relative centrifugal force, centrifugation time, and concentration factor substantially improved red blood cell cast detection. The enhanced protocol may be useful as an additional sediment prepara tion method when glomerular hematuria is suspected, particularly after a negative standard microscopy result.