Which autoantibody has the highest specificity for systemic lupus erythematosus and is included in the SLICC classification criteria?

• A Anti-Smith (Sm) antibody ✓
• B Anti-U1-RNP antibody
• C Anti-Ro (SSA) antibody
• D Antinuclear antibody (homogeneous pattern)

Explanation

Anti-Smith antibody targets components of the U1 snRNP spliceosomal complex and has specificity approaching 99 percent for SLE, though its sensitivity is only around 30 percent. Because of this specificity it carries heavy weight in the SLICC and EULAR/ACR classification criteria. Anti-U1-RNP is characteristic of mixed connective tissue disease, anti-Ro is common in SLE and Sjogren disease but far less specific, and a homogeneous ANA pattern is sensitive but entirely nonspecific, being positive in many autoimmune and even healthy individuals.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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