Urine erythrocyte morphology in patients with microscopic haematuria caused by a glomerulopathy

The evaluation of urinary erythrocyte morphology (UEM) has been proposed for patients with isolated microscopic haematuria (IMH) to early orientate the diagnosis towards a glomerular or a nonglomerular disease. However, to date, the role of this test in patients with IMH has very rarely been investigated. Sixteen patients (ten children, six adults) with persistent IMH classified as glomerular on the basis of repeated UEM evaluations (55 urine samples, two to eight per patient) were submitted to renal biopsy. This showed a glomerular disease in 14/16 patients (87.5%) (nine thin basement membrane disease; three Alport syndrome; two other), whereas in two patients, no abnormalities were found. Of four microscopic criteria investigated to define a IMH as glomerular, >80% dysmorphic erythrocytes were not found in any sample, ≥40% dysmorphic erythrocytes alone were seen in seven samples (12.7%), ≥5% acanthocytes alone in 15 samples (27.3%) and erythrocytic casts in six samples (10.9%). There was ≥40% dysmorphic erythrocytes associated with ≥5% acanthocytes in 25 samples (45.5%). Sensitivity and positive predictive values in diagnosing a glomerular haematuria were 59.2% and 90.6%, respectively, for ≥40% dysmorphic erythrocytes, 69.4% and 85% for ≥5% acanthocytes/G1 cells and 12.2% and 100% for erythrocytic casts. Our findings demonstrate that the evaluation of UEM is useful to identify patients with an IMH of glomerular origin.