Session Information
Date: Tuesday, October 23, 2018
Title: Systemic Sclerosis and Related Disorders – Clinical Poster III
Session Type: ACR Poster Session C
Session Time: 9:00AM-11:00AM
Background/Purpose: The gold standard for anti-Scl-70 antibody testing in systemic sclerosis (SSc) uses immunodiffusion (ID) techniques, but enzyme-linked immunosorbent assay (ELISA) and multi-bead technology are often used to save time and cost. There is concern that using this methodology results in an increase in false positive results. Our aim was to assess the performance of the multi-bead, ELISA, and ID testing methods.
Methods: We conducted a retrospective study of patients whose extractable nuclear antigen-10 (ENA-10) autoantibody panel tested positive for the anti-Scl-70 antibody by multi-bead technology during a one-year period. All samples positive by multi-bead were sent to a reference laboratory to be reflexed for ELISA, and all anti-Scl-70 antibodies positive by ELISA were further tested by ID. Clinical data was reviewed by a rheumatologist and assessed for presence of SSc, internal organ involvement, and other connective tissue disease (CTD).
Results: Approximately 9500 extractable nuclear antigen-10 (ENA-10) panels were ordered by physicians at the at our institution between August 2016 and August 2017. Of these, 129 patients were positive for the anti-Scl-70 antibody by multi-bead assay, 51 were positive by ELISA, and 21 were positive by ID. On chart review of the patients who were positive by multi-bead assay, 33 (25.6%) had SSc and 9 (7.0%) had diffuse cutaneous SSc (dcSSc). Twenty-four (18.6%) had other CTDs, with 72 (55.8%) presenting with no evidence of CTD (Table). Of the 51 patients who were positive by multi-bead and ELISA, 23 (45.1%) had a diagnosis of SSc and 8 (15.7%) had dcSSc. Eight (15.7%) were diagnosed with other CTDs. For the 21 patients who were positive by multi-bead, ELISA and ID, 19 (90.5%) were diagnosed with SSc and 8 (38.1%) had dcSSc. We found that 25.6% of patients positive by multi-bead, 45.1% positive by ELISA, and 90.5% positive by ELISA and ID had SSc.
Conclusion: Multi-bead assays have a high rate of false positive results for the anti-Scl-70 antibody in patients without clinical evidence of SSc. A stepwise approach of confirmation of positive multi-bead results using both ELISA and ID greatly improves the predictive value of antibody testing for the diagnosis of SSc.
Table: Relative frequency of anti-Scl-70 antibody in patients diagnosed with systemic sclerosis, diffuse cutaneous systemic sclerosis and other connective tissue diseases
|
Total n (%)
|
SSc n (%)
|
Diffuse Cutaneous SSc n (%)
|
Other CTDs n (%)
|
|
|
Anti-Scl-70 positive by multi-bead
|
129 (100) |
33 (25.6) |
9 (7.0) |
24 (18.6)
|
|
Anti-Scl-70 Negative by ELISA
|
78 (60.5) |
10 (12.8) |
1 (1.3) |
16 (20.5) |
|
Anti-Scl-70 Positive by multi-bead + ELISA
|
51 (39.5) |
23 (45.1) |
8 (15.7) |
8 (15.7) |
|
Anti-Scl-70 Negative by ID (positive by multi-bead + ELISA)
|
30 (58.8) |
4 (13.3) |
0 (0) |
6 (20.0) |
|
Anti-Scl-70 Positive by multi-bead, ELISA and ID
|
21 (41.2) |
19 (90.5) |
8 (38.1) |
1 (4.8) |
To cite this abstract in AMA style:
Homer K, Warren J, Karayev D, Khanna PP, Young A, Nagaraja V, Metzger AL, Khanna D. Performance of Anti-Scl-70 Antibody Testing By Multiple-Bead, Enzyme-Linked Immunosorbent Assay, and Immunodiffusion in a University Setting [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 9). https://acrabstracts.org/abstract/performance-of-anti-scl-70-antibody-testing-by-multiple-bead-enzyme-linked-immunosorbent-assay-and-immunodiffusion-in-a-university-setting/. Accessed .« Back to ACR/ARHP Annual Meeting 2018
ACR Meeting Abstracts - https://acrabstracts.org/abstract/performance-of-anti-scl-70-antibody-testing-by-multiple-bead-enzyme-linked-immunosorbent-assay-and-immunodiffusion-in-a-university-setting/