Differential Diagnosis
Systemic lupus erythematosus (SLE): when active, usually a homogenous pattern on ANA or less commonly speckled, rim, or nucleolar when present in high enough titer to be clinically significant
Sjögren syndrome: common ANA pattern is speckled; less commonly homogenous
Scleroderma or systemic sclerosis: ANA pattern is most commonly speckled, followed by centromeric and less commonly nucleolar
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Mixed connective tissue disease: ANA pattern is almost always speckled
Rheumatoid arthritis (RA): when ANA positive (about 25-40% of cases), a speckled ANA pattern most commonly
Don't Miss – Dangerous Situations
These are all chronic diseases, and, if there is a life-threatening complication, the complication could be serious.
Commonly Encountered Situations
SLE
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Common autoimmune disorder
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Much more common in women than men (female:male ratio approximately 9:1)
Suggested Additional Lab Testing
For follow-up from a positive ANA test:
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For SLE: anti Ds DNA, anti-SS-A (Ro), anti-SS-B (La), anti-U1 RNP, anti-Sm, and follow-up with serial anti-DS DNA
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For Sjögren syndrome: anti-SS-A (Ro), anti-SS-B (La)
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For polymyositis and adult dermatomyositis: anti-Jo-1
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For mixed connected tissue disease: test for anti-U1 RNP
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For scleroderma: if there is a fine or grainy nuclear pattern, test anti-Scl-70 (topoisomerase I); if there is a centromeric pattern, no additional tests are recommended.
In addition to the follow-up with serologic testing, patients with Sjögren syndrome can be tested for dry eyes and dry mouth by a variety of assays.
Patients with possible inflammatory muscle disease may benefit from creatine kinase testing and/or a muscle biopsy. Evaluation for RA: rheumatoid factor test (found in approximately 80% of patients with RA); x-rays, particularly of hand and wrist for joint disease; C-reactive protein test as an indicator of inflammation with or without SED rate to assess level of inflammation.
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