[Dysmorphic erythrocytes in urinary sediment in differentiating urological from nephrological causes of hematuria]

To determine the significance of dysmorphic erythrocytes in the urinary sediment for discrimination between urological and nephrological causes of haematuria.

Evaluation of diagnostic test.

Departments of Nephrology and Pathology, University Hospital Nijmegen.

Of 107 patients with haematuria in whom renal parenchymal or urological disease was diagnosed, the percentage of dysmorphic erythrocytes was estimated in the unstained urinary sediment with normal light microscopy. By using a Receiver Operating Characteristic curve the cutoff point that provided the highest diagnostic value of the erythrocyte morphology was determined. In addition, the inter-observer variation was estimated in a separate series of 26 urinary sediments.

At a cutoff value of 40% dysmorphic erythrocytes the sensitivity for urological pathology was 100% and the specificity 66.7%. When presence of erythrocyte, haemoglobin or fatty casts was also considered as a criterion for a nephrological diagnosis, the specificity for urological pathology rose to 88.1%. The inter-observer variation showed a correlation coefficient of 0.90 (kappa: 0.77).

Evaluation of the erythrocyte morphology in the urinary sediment is a reliable aid in determining the strategy to be followed in patients with haematuria. It is important, however, that strict criteria for establishing erythrocyte dysmorphism are applied.