Urinary red blood cell volume analysis in the investigation of haematuria.

ABSTRACT

The mean cellular volume (MCV) of urinary red blood cells was measured with an autoanalyser in 85 patients with definite causes of haematuria (31 had glomerulonephritis, 54 urological disorders). We found that red blood cells of glomerular origin had a smaller volume than non-glomerular cells (59.4 +/- 10.23 vs 87.35 +/- 11.17 fl; P less than 0.001). If an MCV equal to 70 fl was taken as the cut-off value between glomerular and non-glomerular haematuria, a correct assessment of the site of bleeding was made in 78 (91.7%) of the 85 patients studied. 'Microcytic' haematuria (i.e., MCV less than 70 fl) was present in 34 patients and correlated strongly with the diagnosis of glomerulonephritis (five false positives, specificity 90.7%; two false negatives, sensitivity 93.5%). Conversely, the presence of larger red blood cells in the urine coincided with the diagnosis of urological disorders in 96.1% (49/51) of the cases.