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ANA Interpretation — SCE Rheumatology MCQ

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EasyAutoimmune SerologyANA InterpretationSCE Rheumatology

A 35-year-old woman is found to have an ANA titre of 1:160 with a homogeneous pattern on indirect immunofluorescence. The test was requested for non-specific symptoms, and she has no clinical features of a systemic autoimmune rheumatic disease. What is the most appropriate interpretation of this result?

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Correct answer: D — It may occur in healthy people and has low predictive value without compatible clinical features.

The correct answer is D. ANA positivity, including at 1:160, occurs in a proportion of otherwise healthy people. Its positive predictive value is therefore low when testing is undertaken without clinical features suggesting a systemic autoimmune rheumatic disease. The titre and staining pattern should be interpreted in the clinical context rather than treated as a diagnosis. Drug-induced lupus requires an appropriate drug exposure and compatible manifestations. Immunosuppression is not indicated for an isolated laboratory abnormality. Although ANA at ≥1:80 is the entry criterion in the 2019 EULAR/ACR SLE classification criteria, additional weighted clinical and immunological criteria are required, and classification criteria are not diagnostic criteria. A homogeneous ANA pattern is not specific for either SLE or Sjögren syndrome.

Reference: Krzemień P et al. Analysis of the impact of sex and age on the variation in the prevalence of antinuclear autoantibodies in Polish population: a nationwide observational, cross-sectional study. Rheumatology International. 2021. https://pubmed.ncbi.nlm.nih.gov/34755204/