EXTRACTABLE NUCLEAR ANTIGEN ANTIBODIES - serum

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Specimen: 5 mL blood in plain tube.

Method: CIE, ID, EIA.

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, Sjögren syndrome La (SS-B) - Sjögren syndrome Scl 70 - scleroderma

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

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