ANA / anti-dsDNA
Formal Definition
Antinuclear antibody (ANA) is an autoantibody screen targeting nuclear antigens, positive in many autoimmune conditions; anti-double-stranded DNA (anti-dsDNA) is a highly specific antibody for SLE that correlates with lupus nephritis disease activity; both are interpreted in the clinical context of symptoms, not as screening tests in asymptomatic populations.
How It's Used on the Ward
"ANA panel" or "send an ANA and dsDNA" — the autoimmune antibody workup ordered when inflammatory or rheumatologic disease is suspected.
Example
""Young woman with joint pain, rash, and renal involvement: ANA 1:640 homogeneous pattern, anti-dsDNA 4x ULN, complement C3/C4 low — highly consistent with active SLE with nephritis. Repeat anti-dsDNA and complement levels will track treatment response.""
Clinical Context
ANA interpretation: titer matters. 1:40 positive in ~25% of healthy population (low specificity). 1:160 or higher raises suspicion; 1:640+ strongly suggests autoimmune disease. Pattern matters less than specific antibody profile. Specific antibodies: anti-dsDNA (SLE), anti-Sm (SLE-specific), anti-Ro/SSA (Sjogren, SLE, neonatal lupus), anti-La/SSB (Sjogren), anti-histone (drug-induced lupus), anti-topoisomerase I (diffuse scleroderma), anti-centromere (CREST syndrome). ANA cascade: positive ANA → order specific antibody panel. Low complement (C3/C4) + high anti-dsDNA = lupus flare pattern. Do NOT order ANA in patients without clinical signs of autoimmune disease — high false positive rate leads to diagnostic confusion.
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