Kidney Week

Abstract: PO1472

A Comparison of aPLA2Rab Assays on Treatment with Cyclophosphamide and Steroids

Session Information

• Glomerular Diseases: Immunology and Inflammation in IgANP, C3GP, TMA, and Nephrotic Diseases
  November 04, 2021 | Location: On-Demand, Virtual Only
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1202 Glomerular Diseases: Immunology and Inflammation

Authors

• Vink- van Setten, Coralien, Radboudumc, Nijmegen, Gelderland, Netherlands

Coralien Vink- van Setten, MD

• van de Logt, Anne-Els, Radboudumc, Nijmegen, Gelderland, Netherlands

Anne-Els van de Logt,

• Kühnl, Alexander, EUROIMMUN Medizinische Labordiagnostika AG, Lubeck, Schleswig-Holstein, Germany

Alexander Kühnl,

• Wetzels, Jack F., Radboudumc, Nijmegen, Gelderland, Netherlands

Jack F. Wetzels,

Background

Anti-PLA2r antibodies (aPLA2r) are present in ~75% of patients with primary membranous nephropathy (MN). A qualitative immunofluorescence test (IIFT) allows accurate detection of aPLA2r, additionally ELISA and ChLIA provide quantitative analysis. Sensitivity of the two latter methods after start of immunosuppressive therapy is not well studied.

Methods

We retrieved stored samples of patients with aPLA2R associated MN, who were treated with cyclophosphamide and steroids(CP), collected at baseline and 8 weeks after start of therapy. Assays were performed by the EUROIMMUN researchlab, Lübeck, Germany. All samples were analysed by IIFT, ELISA and ChLIA. We categorized ELISA results to cut-off values used in literature: 2, 14, and 20 RU/ml resp.

Results

We included baseline samples of 50, and 8 week samples of 51 patients. At baseline, all patients tested IIFT positive; ELISA test was positive in 94% or 98% of samples using cut-off values of 20 RU/ml or 14 RU/ml resp., indicating high sensitivity. Agreement between IIFT and ChLIA was 100%. After 8 weeks on CP, 37/51 patients had immunological remission by IIFT. ELISA test results are given in Table1. In the IIFT positive samples collected after 8 weeks, ELISA titers were < 20RU/ml or < 14 RU/ml in 9/14 and 5/14 patients respectively, suggesting lower sensitivity. All IIFT negative samples had ELISA titers < 14 RU/ml. When analysing IIFT negative patients with ELISA titer <2 U/mL (N=23) vs. 2-14 U/mL (N=14), persistent immunological and clinical remission was better in the first group (74% vs 58%), however not statistically different. With ChLIA only 4/51 (8%) had different results (2 IIFT+/ChLIA-, 2 IIFT-/ChLIA+); resulting in a sensitivity of 86% and a specificity of 95%, when compared to IIFT.

Conclusion

Using immunological remission as treatment target, as described here after 8 weeks of CP, requires evaluation of the applied assay for this purpose. Of the examined quantitative methods, ChLIA demonstrated the highest agreement with IIFT. ELISA titers below the recommended cut-off for initial diagnosis still show a tendency towards the clinical outcome, which could be investigated by further studies.

Funding

• Commercial Support –