Autoimmune Disease Diagnosis Guidelines

Introduction to Autoimmune Disease Testing

The American Journal of Respiratory and Critical Care Medicine recommends testing for creatine phosphokinase, myoglobin, aldolase, antisynthetase antibodies, and other specific antibodies for suspected inflammatory myopathies 1
The American College of Rheumatology suggests that anti-Sm antibodies have high diagnostic specificity for Systemic Lupus Erythematosus (SLE) and produce a coarse speckled pattern on ANA testing 3

For suspected SLE, the European League Against Rheumatism recommends ordering antinuclear antibody (ANA) by immunofluorescence assay, anti-dsDNA antibodies, anti-Smith (Sm) antibodies, complement levels, and complete blood count 2, 3
Anti-dsDNA antibody testing should be performed using either Crithidia luciliae immunofluorescence test or solid phase assays, as recommended by the European League Against Rheumatism 2

For suspected Sjögren's syndrome, the American College of Rheumatology recommends ordering anti-SSA/Ro antibodies, anti-SSB/La antibodies, ANA, rheumatoid factor, and other specific biomarkers 4
A point-of-care test is available that includes traditional serology as well as additional biomarkers for Sjögren's syndrome, as reported in Ophthalmology 4

For suspected MCTD, the European League Against Rheumatism recommends ordering ANA, anti-U1RNP antibodies, anti-Sm, anti-SSA/Ro, and anti-SSB/La 2
Anti-U1RNP antibodies are the defining serological feature of MCTD and produce a coarse speckled pattern on ANA testing, according to the European League Against Rheumatism 2

For suspected systemic sclerosis, the American College of Rheumatology recommends ordering ANA, anti-Scl-70/topoisomerase-1, anti-centromere, and other specific antibodies 1
Anti-topoisomerase-1 (Scl-70) antibodies are associated with diffuse cutaneous systemic sclerosis, as reported in Praxis Medical Insights 2

For suspected Guillain-Barré syndrome, the American Academy of Neurology recommends ordering anti-ganglioside antibodies and considering testing for recent infections 5
Specific anti-ganglioside antibody patterns correlate with clinical variants of Guillain-Barré syndrome, according to the Journal of Allergy and Clinical Immunology 5

ANA testing by indirect immunofluorescence assay on HEp-2 cells is the reference method for initial screening, with a recommended screening dilution of 1:160, as recommended by the American College of Rheumatology 6, 7
Different ANA patterns suggest different autoantibodies and associated conditions, according to Praxis Medical Insights 2
The method used for antibody detection should always be specified in the test result, as reported in Annals of the Rheumatic Diseases 6, 7

Not all positive ANA tests indicate autoimmune disease; up to 25% of healthy individuals can have positive ANA, as reported in Annals of the Rheumatic Diseases 7
Low-titer positive ANA results should be interpreted with caution, according to Praxis Medical Insights 2
Some autoantibodies may be present in ANA-negative patients, as reported in Praxis Medical Insights 2