Glomerular Hematuria for the Diagnosis of Glomerulonephritis

Introduction: Reports on the performance of glomerular hematuria for the diagnosis of glomerulonephritis (GN) show heterogeneity in the results and used urological pathologies as controls. We hypothesized that identification of urinary acanthocytes (uACANTHO) and/or urinary red blood cell casts (uRBCCs) by comprehensive microscopic examination of the urinary sediment (uMICRO) can differentiate glomerular disease from non-glomerular renal pathology. Methods: Records of patients seen for consultation for acute kidney injury or proteinuria/ hematuria who had specimens examined by uMICRO and a kidney biopsy performed within 2 weeks of uMICRO were extracted. We assessed the sensitivity (SENS), specificity (SPEC), and positive and negative predictive value (PPV, NPV) of uACANTHO and/or uRBCC for the diagnosis of biopsy-proven GN or for any glomerulopathy (GP). Results: Of 915 patients who completed uMICRO, 276 patients were included (mean age 53, 54% women). Median serum creatinine was 3.5 mg/dL. A total of 219 (79%) were categorized as GP, whereas 57 (21%) had non-GP diagnosis (e.g., tubular). Within the GP category, 114 (41%) had GN (e.g., IgA nephropathy, pauci-immune GN), whereas 105 (38%) had non-GN GP (e.g., podocytopathies). The SENS, SPEC, PPV, and NPV of uACANTHO for diagnosing GN were 68%, 86%, 78%, and 79%, respectively, whereas for GP SENS, SPEC, PPV, and NPV were 45%, 100%, 100%, and 32%, respectively. For GN, combining uACANTHO and/or uRBCC resulted in improvement of the SENS, SPEC, PPV, and NPV to 75%, 86%, 79%, and 83%, respectively. Either uACANTHO or uRBCC were found in 47/51 (92%) cases of crescentic/ necrotizing GN. Conclusion: Identification of glomerular hematuria by uMICRO aids in the diagnosis of GN. Combining the identification of uACANTHO and uRBCC enhances the diagnostic yield of uMICRO for GN and offers good NPV for crescentic/necrotizing GN. uACANTHO are pathognomonic for GP.