Each rheumatic disease typically exhibits a characteristic antinuclear antibody (ANA) profile. Therefore, identifying the specific ANA pattern in a patient’s serum is valuable for the differential diagnosis of autoimmune connective tissue diseases. The Sm (Smith) antigen is a highly specific serologic marker found in approximately 20–30% of patients with systemic lupus erythematosus (SLE). Antibodies to RNP (ribonucleoprotein) are detected in several rheumatic diseases; however, a high-titer anti-RNP response is most commonly associated with Mixed Connective Tissue Disease (MCTD). Antibodies to SSA/Ro and SSB/La are observed most frequently in Sjögren’s syndrome, though they also occur in a significant proportion of patients with SLE. Additionally, anti-SSA/Ro antibodies have been associated with congenital heart block in neonates born to affected mothers. This ELISA test detects autoantibodies to RNP, Sm, SSA/Ro, and SSB/La in human serum.

• Room temperature: up to 8 hours
• 2–8°C: up to 48 hours
• –20°C or below: for longer storage

Send frozen serum on dry ice. Do not freeze samples in self-defrosting freezers.

Enzyme-Linked Immunosorbent Assay (ELISA)

Negative.
Positive results for each ENA antigen are indicated separately.

• Anti-ENA includes Sm and RNP
• Anti-Sjögrens includes SSA and SSB

Kądziela, M., et al. The Art of Interpreting Antinuclear Antibodies (ANAs) in Clinical Practice,
Journal of Clinical Medicine. 2025.

Back to Autoimmune Diseases