The value of comparative volumetric analysis of urinary and blood erythrocytes to localize the source of hematuria

Purpose: We evaluate comparative volumetric analysis of blood and urinary r ed blood cells (RBCs) to identify the source of hematuria. Comparative volu metric analysis is defined as the difference between mean corpuscular eryth rocyte volume in peripheral blood (MCVB) diluted in urine supernatant after centrifugation and mean corpuscular volume of urinary erythrocytes (MCVU). The potential of MCVB-MCVU to distinguish the origin of hematuria is compa red to MCVU alone. The fundamental hypothesis is that RBCs that can go thro ugh the glomerulus will be smaller than those from the collecting system or lower urinary tract, thus having a smaller MCVU and larger difference betw een MCVB and MCVU. Materials and Methods: A prospective detailed urological evaluation was per formed on 210 patients with glomerular or nonglomerular hematuria detected by urinary sediment, clinical radiological evaluation, endoscopy, cytology and sometimes bladder or renal biopsy. After evaluation 24 cases with an un certain source of hematuria were excluded from study. Specialized urinalysi s, volumetric analysis and clinical investigation were performed in a blind fashion. MCVU and MCVB-MCVU were registered for every patient. The Technic on* H-3 system with angle laser scattering dual system allowed measurement of mean corpuscular volume in a minimal number of RBCs, and resuspension of RBC pellets in the same urinary supinate avoided effects of osmolarity and pH on RBC size and shape. Reproducibility in assessing the index was teste d in 50 cases in which comparative volumetric analysis was repeated on 2 co nsecutive days. Unpaired t test was performed, and a threshold value of MCV B-MCVU with maximum sensitivity and specificity to detect glomerular hematu ria was identified. The potential of urinary and comparative volumetric ana lysis to distinguish the source of hematuria was evaluated and compared by receiver operating characteristics curve analysis. Results: Hematuria was nonglomerular in 53 (28.4%) and glomerular in 133 (7 1.6%) patients. Mean MCVB-MCVU was significantly different for nonglomerula r (0.6 fl.) and glomerular (30.5 fl.) sources (p <0.0001). There was a corr elation between repeat independent measures of MCVU and MCVB-MCVU. The high est positive predictive value to detect a glomerular origin is desirable so that unnecessary investigation can be obviated without the risk of missing a nonglomerular source. With a limit of 16 fl. specificity and positive pr edictive value were 98 and 99%, respectively. Receiver operating characteri stics curve analysis to localize the source of hematuria revealed significa nt differences in favor of comparative volumetric analysis versus urinary v olumetric analysis alone. Conclusions: MCVB-MCVU using the Technicon H-3 system is a useful noninvasi ve and accurate method to locate the source of hematuria. A value of 16 fl. or greater practically rules out a nonglomerular origin and obviates furth er urological investigation. We have incorporated this investigation in our diagnostic algorithm for hematuria.