Unit Code 800219:
Jo 1 Antibodies, IgG, Serum
Useful For
Evaluating patients with signs and symptoms compatible with a
connective tissue disease, especially those patients with muscle
pain and limb weakness, concomitant pulmonary signs and
symptoms, Raynaud's phenomenon, and arthritis
Clinical Information
Jo 1 (histidyl tRNA synthetase) is a member of the amino acyl-tRNA
synthetase family of enzymes found in all nucleated cells. Jo 1
antibodies in patients with polymyositis bind to conformational
epitopes of the enzyme protein and inhibit its catalytic activity in
vitro.(1)
Jo 1 antibodies are a marker for the disease polymyositis, and occur
most commonly in myositis patients who also have interstitial lung
disease. The antibodies occur in up to 50% of patients with
interstitial pulmonary fibrosis and symmetrical polyarthritis.(2)
See "Connective Tissue Diseases Cascade Test-Ordering Algorithm"
in Special Instructions and "Optimized Laboratory Testing for
Connective Tissue Diseases in Primary Care: The Mayo Connective
Tissue Diseases Cascade" in Publications.
Reference Values
<1.0 U (negative)
> or =1.0 U (positive)
Reference values apply to all ages.
Interpretation
A positive result for Jo 1 antibodies is consistent with the diagnosis
of polymyositis and suggests an increased risk of pulmonary
involvement with fibrosis in such patients.
Cautions
Testing for antibodies to Jo 1 is not useful in patients with a negative
test for antinuclear antibodies (ANA).
A negative test for Jo 1 antibodies does not exclude the diagnosis of
polymyositis or dermatomyositis.
Special Instructions and Forms
Clinical Reference
1. Targoff I: Autoantibodies in polymyositis. Rheum Dis Clin North
Am 1992;18:455
2. Leff R, Sherman J, Plotz P: Inflammatory muscle diseases. In
Clinical Immunology Principles and Practice, 2nd edition. Edited
by R Rich, T Fleisher, W Shearer, B Kotzin, et al. St. Louis, Mosby-
Year Book, 2001, Chapter 65, pp 65.1-65.8
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