Volumetric analysis of urinary erythrocytes: a standardized methodology to localize the source of haematuria.

Volumetric analysis of urinary red blood cells (RBCs) was performed in two groups of patients: (a) 91 with glomerulonephritis (GN), 158 with non-glomerular diseases (non-GN) and 53 controls without haematuria; (b) 97 with GN and 41 with non-GN diagnoses and greater than or equal to 2+ haematuria, analysed after modified sample preparation (isotonic dilution and haemolysis to eliminate non-RBC debris). In group A, diagnostic ranges were established for modal, mean and differential (urinary-peripheral blood modal) RBC volumes to differentiate GN from non-GN sources of blood loss according to RBC size. 54% (135/249) of modal volumes and 68% (124/183) with greater than or equal to 2+ haematuria were within a diagnostic range of values, i.e. 40-180 fl (sensitivity), and the source of haematuria was correctly identified in 85% (115/135) and 87% (108/124) of these, respectively (specificity). Of the remainder, with modal volumes less than 40 or greater than 180 fl, 45% (51/114) were from GN and 55% (63/114) from non-GN specimens, along with 94% (48/53) controls without haematuria (non-diagnostic analyses). In contrast, whilst 90% (74/82) of mean volumes greater than or equal to 110 fl and 94% (62/66) of differential volumes greater than or equal to 0 fl were from non-GN specimens, values below these were common to both diagnostic groups so that diagnostic sensitivities were reduced to 38% (82/219) and 34% (66/193), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)