Objectives A perception derived from cross-sectional studies of small systemic lupus erythematosus (SLE) cohorts is that there is a marked discrepancy between antinuclear antibody (ANA) assays, which impacts on clinicians’ approach to diagnosis and follow-up. We compared three ANA assays in a longitudinal analysis of a large international incident SLE cohort retested regularly and followed for 5 years.
Methods Demographic, clinical and serological data was from 805 SLE patients at enrolment, year 3 and 5. Two HEp-2 indirect immunofluorescence assays (IFA1, IFA2), an ANA ELISA, and SLE-related autoantibodies were performed in one laboratory. Frequencies of positivity, titres or absorbance units (AU), and IFA patterns were compared using McNemar, Wilcoxon and kappa statistics, respectively.
Results At enrolment, ANA positivity (≥1:80) was 96.1% by IFA1 (median titre 1:1280 (IQR 1:640–1:5120)), 98.3% by IFA2 (1:2560 (IQR 1:640–1:5120)) and 96.6% by ELISA (176.3 AU (IQR 106.4 AU–203.5 AU)). At least one ANA assay was positive for 99.6% of patients at enrolment. At year 5, ANA positivity by IFAs (IFA1 95.2%; IFA2 98.9%) remained high, while there was a decrease in ELISA positivity (91.3%, p<0.001). Overall, there was >91% agreement in ANA positivity at all time points and ≥71% agreement in IFA patterns between IFA1 and IFA2.
Conclusion In recent-onset SLE, three ANA assays demonstrated commutability with a high proportion of positivity and titres or AU. However, over 5 years follow-up, there was modest variation in ANA assay performance. In clinical situations where the SLE diagnosis is being considered, a negative test by either the ELISA or HEp-2 IFA may require reflex testing.
- Systemic Lupus Erythematosus
Data availability statement
All data relevant to the study are included in the article. Not applicable.
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Handling editor Josef S Smolen
Contributors All authors were involved in the concept and design, data analysis and interpretation, and editing for intellectual content. MYC, AEC, MJF and KHC were involved in manuscript drafting. MC is responsible for the overall content as the guarantor.
Funding The cost of the immunoassay supplies and labor were supported by the Lupus Foundation of America and MitogenDx. MYC is supported by the Lupus Foundation of America Gary S. Gilkeson Career Development Award and research gifts in kind from MitogenDx (Calgary, Canada). AEC holds The Arthritis Society Research Chair in Rheumatic Diseases at the University of Calgary. KHC is supported by NIH K24 AR066109. JH work was supported by the Canadian Institutes of Health Research (research grant MOP-88526). CG work was supported by Lupus UK, Sandwell and West Birmingham Hospitals NHS Trust and the NIHR /Wellcome Trust Clinical Research Facility in Birmingham. S-CB work was supported by the Korea Healthcare technology R & D project, Ministry for Health and Welfare, Republic of Korea (A120404). The Montreal General Hospital Lupus Clinic is partially supported by the Singer Family Fund for Lupus Research. AR and DI are supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre. The Hopkins Lupus Cohort is supported by NIH Grants AR043727 and AR069572. PRF presently holds a tier 1 Canada Research Chair on Systemic Autoimmune Rheumatic Diseases at Université Laval, and part of this work was done while he was still holding a Distinguished Senior Investigator of The Arthritis Society. INB is an NIHR Senior Investigator Emeritus and is funded by the National Institute for Health Research Manchester Biomedical Research Centre and the NIHR/Wellcome Trust Manchester Clinical Research Facility. The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health. MAD work was supported by the NIH grant RR00046. RR-G work was supported by the NIH (grants 1U54TR001353 formerly 8UL1TR000150 and UL-1RR-025741, K24-AR-02318, and P60AR064464 formerly P60-AR-48098). SM is supported by grants R01 AR046588 and K24 AR002213 GR-I is supported by the Department of Education, Universities and Research of the Basque Government. SJ is supported by the Danish Rheumatism Association (A1028) and the Novo Nordisk Foundation (A05990).
Competing interests MYC has received consulting fees from Janssen and MitogenDx (less than US$10 000). AEC has received consulting fees from AstraZeneca, BristolMyersSquibb, and Glaxo Smith Kline (less than US$10 000 each). KCH has consulted for or collaborated on research projects with Janssen, Glaxo Smith Kline, Exagen Diagnostics, Eli Lilly, Merck Serono, Astra Zeneca and Neutrolis (less than US$10 000 each). CG has received consulting fees, speaking fees, and/or honoraria from AstraZeneca, Abbvie, Amgen, UCB, GlaxoSmithKline, Merck Serono and BMS (less than US$10 000 each) and grants from UCB. Grants from UCB were not to CG but to Sandwell and West Birmingham Hospitals NHS Trust. DDG received consulting fees, speaking fees, and/or honoraria from GlaxoSmithKline (less than $10 000). INB has received consulting fees, speaking fees and/or honoraria from Eli Lilly, UCB, Roche, Merck Serono, MedImmune (less than US$10 000 each) and grants from UCB, Genzyme Sanofi and GlaxoSmithKline. EMG has paid consultation with investment analysts Guidepoint Global Gerson Lerman Group.Dr. Kalunian has received grants from UCB, Human Genome Sciences/GlaxoSmithKline, Takeda, Ablynx, Bristol-Myers Squibb, Pfizer and Kyowa Hakko Kirin, and has received consulting fees from Exagen Diagnostics, Genentech, Eli Lilly, Bristol-Myers Squibb, and Anthera (less than US$10 000 each). MJF is Director of Mitogen Diagnostics Corporation (Calgary, AB Canada) and a consultant to Werfen International (Barcelona, Spain), Grifols (Barcelona, Spain), Janssen Pharmaceuticals of Johnson & Johnson and Alexion Canada (less than US$10 000 each). The remainder of the authors have no disclosures.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
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