Differentiation of hematuria using a uniquely shaped red cell

Although variously shaped urinary red cells have been reported in glomerulonephritic hematuria, no specific shapes with concrete definition have been proposed. This made morphological differentiation of hematuria vague and caused different results among different observers. To solve these problems and improve the diagnostic rate, we employed a uniquely shaped red cell, which only appeared in glomerulonephritic hematuria, as a probe for diagnosis. We studied 182 hematuria cases from 90 glomerulonephritic patients and 95 hematuria cases from 68 urological disease patients. Fresh urine was collected and observed by differential interference microscopy. The red cell, referred to as G1, has a distinctive doughnut-like shape with blebs and was highly specific for glomerulonephritic hematuria. Occurrence of G1 cells increased at lower pH an higher osmolality of urine. A presence of 5% or more G1 cells could be an indicator of glomerulonephritic hematuria. Specificity and sensitivity of this criterion were 100 and 73%. However, when only acidic concentrated urine (pH < or = 6.4, osmolality > or = 400 mosm/kg H2O) was used, the specificity and sensitivity increased to 100 and 99.2%, respectively. Glomerulonephritic and urological hematuria were correctly diagnosed by counting the urinary red cells with doughnut-like shape in acidic and concentrated urine. This method seems to be superior to others in diagnostic rate, simplicity and clarity.