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Anti-Nuclear Antibody Tests

Anti-Nuclear Antibody Tests. Regan Arendse FCP(SA), PhD Rheumatologist Saskatoon. Case study. Questions . Is the ANA a useful clinical tool? What causes a false positive ANA? When should an ANA test be requested?. Rates of positive ANA in healthy and ill.

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Anti-Nuclear Antibody Tests

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  1. Anti-Nuclear Antibody Tests Regan Arendse FCP(SA), PhD Rheumatologist Saskatoon

  2. Case study

  3. Questions • Is the ANA a useful clinical tool? • What causes a false positive ANA? • When should an ANA test be requested?

  4. Rates of positive ANA in healthy and ill Wandstrat et al., J Autoimmun 2006; 27: 153-60

  5. Gender and positive ANA Quan-Zhen et al., Arth Res Ther 2011

  6. Age and positive ANA • No association between age (20-60 years) and ANA positivity Quan-Zhen et al., Arth Res Ther 2011 Tan et al., Arth & Rheum 1997; 40: 1601-11

  7. Accumulated % + antibodies over 10 years before diagnosis with SLE Erikson et al., Arth Res Ther 2011; 13

  8. Antibody presence predating disease Erikson et al., Arth Res Ther 2011; 13

  9. Predictive value of ANA for SLE • Incidence rate of SLE, lupus develops in <1% positive ANA individuals • None of 24 ANA asymptomatic children developed disease over mean 61 month follow up period • Predictive value of ANA increases in the at risk population with clinical disease Aho et al., J Rheum 1992; 19: 1377-9 Cabral et al., Pediatrics 1992; 89: 441-4

  10. Answer • The ANA is not a good screening tool for auto-immune disease in the absence of convincing clinical signs • Long time interval between ANA positivity and onset of disease does not warrant screening • Lack of any effective pre-emptive or prophylactic treatment emphasizes that the argument not to routinely request an ANA

  11. What causes a false positive ANA?

  12. HEp-2 indirect immunofluorescence

  13. Antigens with similar structure to pathologic antigens • Viruses (Herpes viruses and HIV) • Drugs which alter proteins (Procainamide, INH, Phenytoin) • Malignant cells • Environmental toxins (silicone)

  14. When should an ANA test be requested? • Yes if strong clinical suspicion of autoimmune disease • Scleroderma • Lupus • Dermatomyositis • Sjogren’s disease • Mixed connective tissue disease

  15. When should an ANA test be requested? • No if not a strong clinical suspicion of autoimmune disease • Chronic pain • Chronic fatigue • Chilblains • Raynaud’s phenomenon • Rosacea

  16. When should an ANA test be requested? • 8.8% of fibromyalgia patients have +ANA • 8.9% of controls have +ANA • In prospective study over 4 years, in 12 with FMS and 12 controls, one in FMS group developed SLE and one in controls developed Sjogren’s syndrome Al Allaf et al., ClinRheuma 2002; 21: 472-7

  17. Conclusion • ANA should not be routinely requested • ANA should not be requested for non-specific symptoms • ANA should only be requested in patients with clinical features strongly suggestive of an auto-immune disease • Causes of false positives are many and varied

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