Antiphospholipase A₂Receptor Autoantibodies: A Comparison of Three Different Immunoassays for the Diagnosis of Idiopathic Membranous Nephropathy

Abstract

Background. The recent identification of circulating autoantibodies directed towards the M-type phospholipase A2 receptor (PLA2R) has been a major advancement in the serological diagnosis of idiopathic membranous nephropathy (IMN), a common cause of nephrotic syndrome in adults. The goal of this study was to compare the performance characteristics of two commercial assays as well as the first addressable laser bead immunoassay (ALBIA) developed for the detection of anti-PLA2R antibodies. Methods. Serum samples of 157 IMN patients and 142 controls were studied. Samples were tested by a cell based immunofluorescence assay (CBA-IFA, Euroimmun, Germany), by ELISA (Euroimmun), and by a novel ALBIA employing an in vivo expressed recombinant human PLA2R. Results. Overall, the three assays showed significant qualitative and quantitative correlation. As revealed by receiver operating characteristic analysis, the ALBIA correlated better with the CBA-IFA than the ELISA (P = 0.0003). The clinical sensitivities/specificities for IMN were 60.0% (51.0–68.5%)/98.6% (95.0–99.8%) and 56.2% (47.2–64.8%)/100.0% (97.4–100.0%) for ALBIA and CBA-IFA, respectively. Conclusion. The ALBIA represents a promising assay for the detection of anti-PLA2R antibodies showing similar performance to the CBA-IFA and the advantage of ease of use and suitability for high throughput, rapid turnaround times, and multiplexing.

Anti-Phospholipase A2 Receptor Antibody as Prognostic Indicator in Idiopathic Membranous Nephropathy

“…A recent study where the same kit was used has already affirmed the suitability of the cutoff values of 14 or 20 U/ ml. Only small differences were found in the sensitivity and specificity rates with a similar prediction rate in receiver operating characteristic analysis for diagnosis [24] .…”

“…In 2 studies evaluating Asian populations, one detected aPLA2R in 82% of Chinese patients and the other showed a positive rate of 69% in Korean patients with IMN [17,25] using WB technique. Several studies showed that PLA2R-Ab rate varies from 52-74% when using the IFT in European populations [20,23,24,27] . The custom-made ELISA was also used to detect PLA2R-Ab in samples of almost all European IMN patients with reportedly inconsistent rates of 47 and 72% [22,23] .…”

“…Similarly, the limitations of WB are its complexity and time constraints; therefore, it is not useful for application in a large population. The recently developed addressable laser bead immunoassay (ALBIA) is a high throughput technique, but the associations between the ALBIA titers from this technique and various clinical parameters have not been established [24,28] . We identified the concordant rate between the quantitative results from the ELISA tests and semi-quantitative data from the WB test.…”

“…We set the cutoff value at 14 U/ml. The manufacturer recommends using 14 or 20 U/ml, which has been validated in a recent study [24] . Forty-three of 93 patients with IMN were already tested with WB technique using human glomerular proteins in non-reducing conditions in our previous study [25] .…”

Comparison of biomarkers between PLA2RAb+ and PLA2RAb− in patients with idiopathic membranous nephropathy

“…PLA2RAb were found in Japanese patients with IMN. The recent identification of circulating autoantibodies directed toward the PLA2R has been a major advancement in the serological diagnosis of idiopathic membranous nephropathy (IMN) [13]. Patients with high PLA2RAb levels achieved remission of proteinuria significantly later than patients with low PLA2R antibody levels.…”