Autoimmune serology
Antinuclear antibodiesANA
Screening test for systemic autoimmune disease — high sensitivity, low specificity.
Sample
Serum
Clinical reference range
— to 1 :80 negative
HEp-2 IFA titer
Conv: —–1 :80 negative
Biology
What it measures
Autoantibodies against nuclear antigens. Reported as titer + pattern (homogeneous, speckled, nucleolar, centromere, nuclear-dot).
Clinical use
Why we order it
Workup of suspected SLE, Sjögren, scleroderma, mixed connective tissue disease, autoimmune hepatitis.
Pitfalls
Pre-analytic & interpretation traps
- !Positive in 5–15% of healthy adults at 1:80 — clinical context required.
- !Negative ANA effectively rules out SLE (>95% sensitivity).
- !Use IFA on HEp-2 cells, not multiplex bead assays, when SLE pretest probability is meaningful.
Follow-up orders
Logical next-step labs
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