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Abstract: PO1571

Detection of Urinary Acanthocytes for the Diagnosis of Glomerulonephritis

Session Information

Category: Glomerular Diseases

  • 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Ramanand, Akanksh, Ochsner Medical Center - New Orleans, New Orleans, Louisiana, United States
  • Kanduri, Swetha Rani, Ochsner Medical Center - New Orleans, New Orleans, Louisiana, United States
  • Varghese, Vipin, Ochsner Medical Center - New Orleans, New Orleans, Louisiana, United States
  • Rosenbloom, Sarah Parent, Ochsner Medical Center - New Orleans, New Orleans, Louisiana, United States
  • Velez, Juan Carlos Q., Ochsner Medical Center - New Orleans, New Orleans, Louisiana, United States
Background

Acanthocyturia is a specific indicator of glomerulonephritis (GN). However, it is reported that the sensitivity of acanthocyturia for the diagnosis of GN is merely around 50%. Examiner expertise is expected to affect the ability to identify urinary acanthocytes. Thus, we hypothesized that in a well-equipped laboratory with proficient observers, the sensitivity of acanthocyturia for the diagnosis of GN can be improved.

Methods

In our institution, we have established a prospective data collection of individuals seen in nephrology consultation who had urine specimen subjected to microscopic examination (MicrExUrSed) as part of the clinical evaluation. Within this cohort, we identified cases in which a kidney biopsy was performed within 2 weeks of the MicrExUrSed. We assessed the performance of acanthocyturia in the diagnosis of biopsy-proven GN. Acanthocyturia reflects glomerular hematuria caused by forms of glomerular disease characterized by injury to the endothelium, mesangium, glomerular basement membrane or blood vessel, but not injury to the podocyte that classically presents with proteinuria. Therefore, podocytopathies were grouped with other diagnoses (tubular, interstitial, etc.) as non-GN

Results

Among 390 patients with MicrExUrSed, 70 underwent kidney biopsy and were included. Mean age was 55 years, 50% were women. White race accounted for 52% and self-identified black race for 39%. Mean serum creatinine was 4.2 mg/dL. Biopsy diagnosis was GN in 27 (39%) and non-GN in 43 (61%). The sensitivity of acanthocyturia for GN diagnosis was 74% (95% CI 53-89%), while the specificity was 86% (95% CI 72-95%). Five of 6 false positive cases had diabetic nephropathy. The positive predictive value of acanthocyturia for GN diagnosis was 77% (95% CI 61-88%) and the negative predictive value 84% (95% CI 73-91%). Acanthocyturia was predominantly detected in pauci-immune GN and IgA nephropathy, with both diagnoses accounting for 14 of the 19 (74%) cases. The hospital laboratory did not report acanthocyturia in any case and misreported it as “yeast” in 2 cases.

Conclusion

With optimal proficiency, the sensitivity of acanthocyturia can be significantly greater than previously reported. Because hospital laboratories do not report it, attempting identification of urinary acanthocytes by nephrologists should be encouraged.