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SLE Criteria Immunology Scoring — SCE Rheumatology MCQ

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ModerateAutoimmune SerologySLE Criteria Immunology ScoringSCE Rheumatology

A 38-year-old woman is being assessed using the 2019 EULAR/ACR classification criteria for systemic lupus erythematosus. She has had an ANA titre of 1:160 on HEp-2 immunofluorescence and has acute cutaneous lupus, low C3 and C4, and anti-dsDNA antibodies detected using an assay with demonstrated specificity of at least 90% for SLE. All findings are attributable to SLE. Only the highest-weighted criterion within each domain is counted. How many points does the anti-dsDNA antibody criterion contribute?

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Correct answer: C — 6

Anti-dsDNA antibodies detected by an assay with at least 90% specificity for SLE score 6 points in the SLE-specific antibodies domain. Anti-Sm antibodies carry the same weight, but only one 6-point contribution can be counted from that domain. Low C3 and C4 are in the separate complement domain and contribute 4 points; acute cutaneous lupus contributes 6 points from the mucocutaneous domain. ANA positivity is an obligatory entry criterion and scores no points. Thus this patient would have 16 points overall, but anti-dsDNA itself contributes 6. Two points correspond to antiphospholipid antibodies, while 10 is the overall classification threshold rather than the anti-dsDNA weight. Eight is not the assigned weight for this criterion.

Reference: Aringer M et al. 2019 European League Against Rheumatism/American College of Rheumatology Classification Criteria for Systemic Lupus Erythematosus, Table 2/Figure 2, 2019. https://pubmed.ncbi.nlm.nih.gov/31385462/