Longitudinal analysis of ANA in the Systemic Lupus International Collaborating Clinics (SLICC) inception cohort

May Choi, Ann Clarke, Murray Urowitz, John Hanly, Yvan St Pierre, Caroline Gordon, Sang-Cheol Bae, Juanita Romero-Diaz, Jorge Sanchez-Guerrero, Sasha Bernatsky, Daniel Wallace, David Isenberg, Anisur Rahman, Joan Merrill, R Paul, Dafna Gladman, Ian Bruce, Michelle Petri, Ellen Ginzler, Mary Anne DooleyRosalind Ramsey-Goldman, Susan Manzi, Andreas Jonsen, Graciela Alarcon, Ronald van Vollenhoven, Cynthia Aranow, Meggan Mackay, Guillermo Ruiz-Irastorza, Sam Lim, Murat Inanc, Ken Kalunian, Soren Jacobsen, Christine A Peschken, Diane Kamen, Anca Askanase, Jill Buyon, Karen H Costenbader, Marvin J Fritzler

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Abstract

Objectives: A perception derived from cross-sectional studies of small SLE cohorts is that there is a marked discrepancy between antinuclear antibody (ANA) assays, which impacts on clinician’s 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 five 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 enzyme-linked immunosorbent assay (ELISA), and SLE-related autoantibodies were performed in one central laboratory. Frequencies of positivity, titres/units, 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 (176.3AU [IQR 106.4-203.5]). 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/units. However, over five 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.
Original languageEnglish
JournalAnnals of the Rheumatic Diseases
Early online date25 Mar 2022
DOIs
Publication statusE-pub ahead of print - 25 Mar 2022

Keywords

  • Antinuclear antibodies
  • Systemic Lupus Erythematosus
  • longitudinal
  • performance
  • immunoassays
  • ELISA

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