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What is the clinical significance of a low titer RNP, negative Sm, but Sm/RNP that is very high titer?

I'm uncertain why both individual parts can be so low/negative but together very positive. Is there an assay discrepancy, a false positive?
1 Answer
Mednet Member
Mednet MemberInvited Expert
Rheumatology · Uniformed Services University of the Health Sciences (USUHS)
Answered on · Updated on

Important question as I've seen clinicians incorrectly interpret anti-Sm-RNP as anti-Smith antibody.

The different autoantibodies (RNP, Smith, Sm/RNP) react to different antigens as follows:

  • Anti-RNP can react to multiple components (antigens) of the U1 small nuclear RNP particle (snRNP),
  • Anti-Smith ...

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