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Five Take Home Points about ANCA Testing

November 10 2015 3:00 PM ET via RheumReports RheumReports

On Sunday, I attended a clear and understandable lecture about ANCA testing. Here are my 5 take home points from the talk.

  1. The consensus is that both indirect immunofluorescence (IIF) and ELISA-based assays should be performed. This pair has a high predictive value for ANCA-associated vasculitis if ordered in patients with a high pre-test probability. Unfortunately, many labs (including ours) only perform ELISA testing for PR3 and MPO.

  2. Be careful with cocaine/levamisole-induced vasculitis and bacterial endocarditis as they can both yield positive ANCA testing (both IIF and ELISA). It is probably worthwhile to test all patients for cocaine use as a standard of care.

  3. The ANCA type clearly predicts relapse risk. The risk of relapse is lower for MPO ANCA-positive cases than PR3. Anyone practicing clinically will be able to attest to this! Honestly, I am so thankful for rituximab for maintenance of remission in my PR3 ANCA vasculitides. The biggest challenge is getting the medication paid for!

  4. PR3 ANCA-positive patients respond better to rituximab vs cyclophosphamide. This is from a subgroup analysis of the RAVE trial and needs to be further investigated as the potential impact of this finding is significant.

  5. Serial ANCA testing has limited value for relapse prediction, and treatment decisions should not be based on a test result in isolation. A Dutch group did show that using low-dose cyclophosphamide for rising ANCA titres prevented flares but the benefit-to-risk ratio was debatable. With more widespread use of rituximab, perhaps this pattern will change?


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About the Author

Dr. Andy Thompson
Dr. Andy Thompson

Dr. Andy Thompson is an Associate Professor at Western University and founder of Rheuminfo.com, Rheumtalks.com, and RheumReports.com.

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