What is the role of an antinuclear antibody test in the workup of CNS lupus?

Updated: May 04, 2021
  • Author: Pradeep C Bollu, MD; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Answer

The classic finding of a low C-reactive protein (CRP) level but an elevated erythrocyte sedimentation rate (ESR) or plasma viscosity was seen in about 40% of patients with systemic lupus erythematosus (SLE). In previously undiagnosed patients thought to have SLE, the principal diagnostic study is the antinuclear antibody (ANA) test.

Although many rheumatologists consider this test to be 100% sensitive for diagnosis, a positive ANA result alone is not sufficient for diagnosis. Positive test results are seen in other autoimmune conditions and in a certain percentage of the general population (especially the elderly). Anti-DNA antibody testing is positive in only about 70% of central nervous system (CNS) episodes.

When a positive ANA result is thought to be clinically relevant, follow up with an antibody to native, double-stranded DNA (dsDNA antibody) to confirm the diagnosis of SLE. An autoantibody panel should be checked for related pathogenic antibodies.

ANA and immunofluorescence

El-Chennawi et al concluded that in patients with clinical features of SLE, ANA detection by immunofluorescence is a more sensitive and effective screening. [26] Additionally, the investigators determined that dsDNA titer by ELISA and BILAG score for severity index are the best markers for follow-up. [26]


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