ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 515

Does Multiplex Flow Immunoassay Underdetect SSA and SSB Antibodies? An Evaluation Of The Sjogren’s International Collaborative Clinical Alliance (SICCA) Cohort

Alan N. Baer1, Laura Gutierrez2, Mara McAdams DeMarco3, Mi Y. Lam4, Livia Casciola-Rosen5, Stephen Shiboski6, Caroline Shiboski4 and Lindsey A. Criswell7, 1Division of Rheumatology, Johns Hopkins University School of Medicine, Baltimore, MD, 2Center Tower Ste 5300, Johns Hopkins University, Baltimore, MD, 3Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 4Orofacial Sciences, University of California San Francisco, San Francisco, CA, 5Division of Rheumatology, Johns Hopkins University, Baltimore, MD, 6University of California, San Francisco, San Francisco, CA, 7Department of Medicine, University of California, San Francisco, Rosalind Russell Medical Research Center for Arthritis, San Francisco, CA

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords: ,

Session Information

Title: Sjögren's Syndrome: Clinical Aspects

Session Type: Abstract Submissions (ACR)

Background/Purpose:  

Multiplex flow immunoassays (MFIA) are used by clinical laboratories to test for antibodies to extractable nuclear antigens. The use of blended Ro52 and Ro60 antigens in an MFIA can mask their reactivities, otherwise detectable with single antigen assays (Autoimmun Rev. 2009;8:632). We tested the hypothesis that single antigen solid-phase assays are more sensitive than MFIA for the detection of SSA and SSB antibodies.

Methods:  

We studied 162 consecutively enrolled SICCA registrants selected independently of their serologic results, including 120 with Sjogren’s syndrome (SS) defined by the ACR criteria, and 42 without SS (controls). SSA and SSB antibody testing was performed by a Bio-Rad Bioplex 2200 MFIA (Quest Laboratories) and positive results were expressed in “antibody index” (AI) units and provided as continuous variable measures up to a prespecified upper limit. Levels >6 AI were stratified as strong positive, >3 to ≤6 AI moderate positive, >1 to ≤3 AI weak positive, and ≤1 AI negative. We independently tested the same samples using individual assays for Ro52 and SSB (Quantalite ELISA) and Ro60 (immunoprecipitation using in vitro transcription/translated protein: IVTT-IP). Ro52 and SSB results were stratified as negative (<20 U), weak positive (20-39 U), moderate positive (40-80 U), and strong positive (>80 U). The concordance rate was determined from individuals positive for both plus those negative for both divided by the total.

Results:  

SSA antibodies were detected in 92 (56.8%) subjects by MFIA and in 87 (53.7%) by ELISA/IVTT-IP. SSB antibodies were detected in 66 (40.7%) by MFIA and in 63 (38.9%) by ELISA. The concordance rate for SSA antibody testing was 93.2% and for SSB 90.7%. MFIA detected SSA antibodies in 8 subjects who tested negative for Ro52 and Ro60; 5/8 had weak SSA reactivity. Conversely, 3 subjects had Ro52 (weak reactivity) without Ro60 antibodies, but tested negative for SSA by MFIA. SSB antibodies were detected by MFIA in 9 subjects (weakly in 4) who tested negative by ELISA. Conversely, SSB antibodies were detected in 6 subjects by ELISA (weak reactivity in 3) who tested negative by MFIA. The 26 discordant (positive/negative) results were distributed evenly among the SS and control groups and the positive reactivity was weak in 15, moderate in 7 and strong in 4.

Conclusion:  

MFIA and single antigen solid phase immunoassays had a concordance rate of over 90% in this sample of the SICCA cohort, and there was no evidence that MFIA underperformed relative to the single antigen assays.

Supported by NIH/NIDCR contract N01 DE32636 and NIAMS P30 AR053503

Disclosure:

A. N. Baer,
None;

L. Gutierrez,
None;

M. McAdams DeMarco,
None;

M. Y. Lam,
None;

L. Casciola-Rosen,
None;

S. Shiboski,
None;

C. Shiboski,
None;

L. A. Criswell,
None.

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