Extractable nuclear antigen Ab
Keywords: Extractable nuclear antigen antibody, ENA antibody
5 mL blood in plain tube.
Electrophoresis, ELISA , line blot.
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Performed when the ANA is positive to determine ANA specificities, some of which identify categories of disease with implications important for treatment and prognosis.
Also indicated when there is a high suspicion of connective tissue disease with negative ANA; antibodies to Ro (SS-A) may not be detected by ANA.
The presence of antibodies against extractable nuclear antigen is highly suggestive of systemic rheumatic disease.
Defined antigen specificities include:
RNP - mixed Connective tissue diseases;
Sm - highly specific for SLE;
Ro (SS-A) - subacute cutaneous lupus, associated with recurrent abortion, congenital heart block and Sjögren syndrome;
La (SS-B) - Sjögren syndrome;
Scl 70 - Scleroderma;
Jo-1 antibody - Myositis; and
PMSCL antibody – Polymyositis scleroderma overlap.
Tan EM et al. Clin Immunol Immunopath 1988; 47: 121-141.
Phan T et al. Clinical and Diagnostic Laboratory Immunology Jan 2002: 1 - 7.