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Interpretive Handbook

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Test 82403:
SS-A and SS-B Antibodies, IgG, Serum

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

SS-A/Ro, SS-B/La, RNP, and Sm are autoantigens commonly referred to as extractable nuclear antigens (ENAs). Antibodies to ENAs are common in patients with connective tissue diseases (systemic rheumatic diseases).

 

SS-A/Ro is composed of protein antigens of 52kD and 60 kD combined with cytoplasmic RNA species. SS-A/Ro antibodies occur in patients with several different connective tissue diseases including Sjogren's syndrome, an autoimmune disease that involves primarily the salivary and lachrymal glands (up to 90% of cases); lupus erythematosus (LE) (40%-60% of cases); and rheumatoid arthritis. SS-A/Ro antibodies are associated with childhood LE, neonatal LE, and with congenital heart block in infants born to mothers with LE.(1,2) SS-A/Ro antibodies have also been reported to be associated with features of extraglandular inflammation in patients with LE including vasculitis, purpura, cytopenias, and adenopathy.

 

SS-B/La is composed of a 48-kD protein combined with RNA species. SS-B/La antibodies are found primarily in patients with Sjogren's syndrome or LE, where they occur with frequencies of approximately 60% and 15%, respectively.(1,2) SS-B/La antibodies occur only infrequently in the absence of SS-A/Ro antibodies.

 

See Connective Tissue Disease Cascade (CTDC) in Special Instructions and Optimized Laboratory Testing for Connective Tissue Diseases in Primary Care: The Mayo Connective Tissue Diseases Cascade in Publications.

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluating patients with signs and symptoms of a connective tissue disease in whom the test for antinuclear antibodies is positive, especially those with signs and symptoms consistent with Sjogren's syndrome or lupus erythematosus

Interpretation Provides information to assist in interpretation of the test results

A positive result for SS-A/Ro or SS-B/La antibodies is consistent with connective tissue disease, including Sjogren's syndrome, lupus erythematosus (LE), or rheumatoid arthritis.

 

A positive result for SS-A/Ro antibodies in a woman with LE prior to delivery indicates an increased risk of congenital heart block in the neonate.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Testing for SS-A/Ro and SS-B/La antibodies is not useful in patients without demonstrable antinuclear antibodies.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

SS-A/Ro ANTIBODIES, IgG

<1.0 U (negative)

> or =1.0 U (positive)

Reference values apply to all ages.

 

SS-B/La ANTIBODIES, IgG

<1.0 U (negative)

> or =1.0 (positive) 

Reference values apply to all ages.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Homburger H, Larsen S: Detection of specific antibodies. In Clinical Immunology: Principles and Practice. 1st edition. Edited by R Rich, T Fleisher, B Schwartz, et al. St. Louis, Mosby-Year Book, 1996, pp 2096-2109

2. Kotzin B, West S: Systemic lupus erythematosus. In Clinical Immunology Principles and Practice. 2nd edition. Edited by R Rich, T Fleisher, W Shearer, et al. St. Louis, Mosby-Year Book 2001, pp 60.1-60.24