SS-B/La Antibodies, IgG, Serum
Evaluating patients with signs and symptoms of a connective tissue disease in whom the test for antinuclear antibodies is positive
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
SS-B/La is an extractable nuclear antigen (ENA) composed of a 48-kD protein combined with RNA species. SS-B/La antibodies are found primarily in patients with Sjogrenâ€™s syndrome or lupus erythematosus (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.
SS-B/La is 1 of 4 autoantigens commonly referred to as extractable nuclear antigens (ENAs). The other ENAs are SS-A/Ro, RNP, and Sm. Each ENA is composed of 1 or more proteins associated with cytoplasmic or small nuclear RNA species (snRNP) ranging in size from 80 to 350 nucleotides. Antibodies to ENAs are common in patients with connective tissue diseases (systemic rheumatic diseases) including LE, mixed connective tissue disease, Sjogren's syndrome, scleroderma (systemic sclerosis), and polymyositis/dermatomyositis.
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.
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.
<1.0 U (negative)
> or =1.0 U (positive)
Reference values apply to all ages.
A positive result for SS-B/La antibodies is consistent with connective tissue disease, including Sjogrenâ€™s syndrome and lupus erythematosus.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Testing for SS-B/La antibodies is not useful in patients without demonstrable antinuclear antibodies.
Clinical Reference 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. First 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. Second edition. Edited by R Rich, T Fleisher, W Shearer, et al. St. Louis, Mosby-Year Book, 2001, pp 60.1-60.24