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Abstract: SA-PO724

Urine Red Blood Cell-Derived Microparticle by Flow Cytometry as a Novel Biomarker for Diagnosis of Glomerular Hematuria

Session Information

Category: Pathology and Lab Medicine

  • 1602 Pathology and Lab Medicine: Clinical

Authors

  • Puapatanakul, Pongpratch, Chulalongkorn University, Bangkok, Thailand
  • Charoensappakit, Awirut, Chulalongkorn University, Bangkok, Thailand
  • Praditpornsilpa, Kearkiat, Chulalongkorn University, Bangkok, Thailand
  • Palasuwan, Duangdao, Chulalongkorn University, Bangkok, Thailand
Background

Differentiating glomerular hematuria (GH) from non-glomerular hematuria (NGH) is based on the identification of dysmorphic red blood cell (RBC) by bright field microscopy which is operator-dependent and insensitive. Whether the detection of RBC-derived microparticle (RMP) by flow cytometry which indicates specific injury to RBC can differentiate GH from NGH has never been validated.

Methods

Spot urine was collected from patients with GH, NGH, and healthy non-hematuria volunteers. GH patients were patients with biopsy-proven glomerular disease diagnosed within 3 months while NGH were patients with urinary tract cancer, nephrolithiasis, and post-operative bleeding. Urine was submitted for microscopic study to identify percentage of dysmorphic RBC, and flow cytometry to detect urine RMP. RMP was defined by size (<1 µm) and positive labeling for CD235a and annexin V. The RMP number was normalized by total RBC number (RMP/RBC ratio). All analyses were performed by blinded technician within 2 hours after specimen collection. Receiver Operating Characteristics (ROC) curve analysis was used to demonstrate diagnostic performance of RMP/RBC ratio in diagnosing GH.

Results

There were 29, 29, and 19 participants in GH, NGH, and healthy groups. The most common diagnoses in GH group were lupus nephritis (48.3%), ANCA-associated glomerulonephritis (13.8%), and IgA nephropathy (10.3%) while majority of NGH group were post-operative hematuria (55.2%) and urinary tract cancers (17.2%). RMP was not present in urine from healthy volunteers but were detected in both GH and NGH patients. The RMP/RBC ratio was significantly higher in GH compared to NGH patients (1.06±0.19 vs 0.18±0.04; p<0.001). RMP/RBC ratio at a cut point of 0.40 provided a sensitivity and specificity of 82.8% and 82.8% for diagnosis of GH, respectively. Performance of RMP/RBC ratio was better than the conventional use of dysmorphic RBC percentage according to the area of under the curve of ROC curve analysis (0.90 vs 0.87).

Conclusion

Measurement of urine RMP/RBC ratio by flow cytometry is a more accurate biomarker for diagnosing GH. This biomarker is operator-independent and can serve as a useful test for clinical practice.

Funding

  • Government Support - Non-U.S.