Extractable nuclear antigen (ENA) antibodies - serum

Last updated: Friday, 14, August, 2009

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Item Process
Specimen

5 mL blood in plain tube.

Reference Interval

Qualitative test

Application

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.

Interpretation

The presence of antibodies against extractable nuclear antigen is highly suggestive of systemic rheumatic disease.

Defined antigen specificities include:
RNP - mixed connective tissue disease;
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; and
Scl 70 - scleroderma

Reference

Tan EM et al. Clin Immunol Immunopath 1988; 47: 121-141.

Phan T et al. Clinical and Diagnostic Laboratory Immunology Jan 2002: 1 - 7.