What autoimmune blood tests, such as Antinuclear Antibody (ANA) test, Rheumatoid Factor (RF), or anti-Cyclic Citrullinated Peptide (anti-CCP) antibodies, can be used for a patient presenting with nonspecific body pains?

Autoimmune Blood Tests for Nonspecific Body Pains

For patients presenting with nonspecific body pains, ANA testing should be the first-line autoimmune blood test, followed by more specific antibody tests based on clinical suspicion and ANA results. 1

Initial Testing Approach

First-Line Test

• Antinuclear Antibody (ANA) test:
  • Gold standard method: Indirect Immunofluorescence Assay (IIFA) on HEp-2 cells 1
  • Screening dilution typically 1:160 (abnormal ANA is a titer above the 95th percentile of healthy control population) 1
  • Report should include pattern (nuclear, cytoplasmic, or mitotic) and highest dilution showing reactivity 1

Second-Line Tests (Based on ANA Results and Clinical Presentation)

• If ANA positive:
  • Anti-dsDNA antibodies: Especially if SLE is suspected 1
  • Extractable Nuclear Antigens (ENA) panel:
    • Anti-Ro/SSA and Anti-La/SSB: For Sjögren's syndrome
    • Anti-Sm: Highly specific for SLE
    • Anti-RNP: Mixed connective tissue disease
    • Anti-Scl-70: Systemic sclerosis
    • Anti-Jo-1: Polymyositis/dermatomyositis

Testing Based on Specific Clinical Suspicion

For Inflammatory Arthritis Suspicion

• Rheumatoid Factor (RF): Present in rheumatoid arthritis (RA), but also in other conditions 2
• Anti-Cyclic Citrullinated Peptide (anti-CCP): Higher specificity for RA than RF 2
  • Sensitivity: 53.1%, Specificity: 95.3% 2

For Vasculitis Suspicion

• Anti-neutrophil Cytoplasmic Antibodies (ANCA):
  • c-ANCA (PR3-ANCA): Granulomatosis with polyangiitis
  • p-ANCA (MPO-ANCA): Microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis 1

For Autoimmune Liver Disease Suspicion

• Anti-mitochondrial Antibodies (AMA): Primary biliary cholangitis 1
• Anti-Smooth Muscle Antibodies (SMA): Autoimmune hepatitis 1
• Anti-Liver Kidney Microsomal type 1 (anti-LKM1): Autoimmune hepatitis type 2 1

For Inflammatory Myopathy Suspicion

• Creatine Kinase (CK): Elevated in inflammatory myopathies 1
• Myositis-specific antibodies: Jo-1, Mi-2, SRP 1

Important Considerations

ANA Testing Limitations

• ANA positivity can occur in healthy individuals (especially at low titers) 3
• Positive predictive value of ANA for lupus is only about 2.1% and 9.1% for any ANA-associated rheumatic disease 3
• ANA titers <1:160 rarely indicate ANA-associated rheumatic disease 3
• ANA can be positive in non-autoimmune conditions, including infections 4

Pattern Interpretation

• Homogeneous pattern: Associated with SLE, drug-induced lupus
• Speckled pattern: Various connective tissue diseases
• Nucleolar pattern: Systemic sclerosis
• Centromere pattern: Limited cutaneous systemic sclerosis (CREST syndrome) 5

Testing Pitfalls to Avoid

1. Ordering ANA without clinical suspicion: Most common reason for ANA testing is widespread pain (23.2%), but this has low yield 3
2. Failing to consider non-autoimmune causes: Infections can cause positive ANA 4
3. Over-reliance on a single test: No single test is diagnostic; clinical correlation is essential
4. Ignoring titer levels: Higher titers generally have greater clinical significance 5

When to Refer to Rheumatology

• Positive ANA with symptoms suggestive of autoimmune disease
• Positive ANA with specific autoantibodies
• Suspected inflammatory arthritis with positive RF or anti-CCP 5

By following this structured approach to autoimmune testing in patients with nonspecific body pains, clinicians can improve diagnostic accuracy while avoiding unnecessary testing and false positive results.