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ANA & ENA Interpretive Guide

Normally, one does not develop antibodies to self antigens. A key function of the immune system is to distinguish foreign antigens (such as from infectious agents) from one’s own tissues. Immune disorders exist when one’s immune system begins generating potentially destructive antibodies to self antigens (autoantibodies). Most autoimmune disorders can be classified as either non-organ specific (systemic) or organ specific.

In non-organ specific or systemic autoimmune disease, tissue injury and inflammation occur in multiple sites in organs without relation to their antigenic makeup and are usually initiated by tissue deposition of circulating immune complexes. These immune complexes are formed by autoantibody responses to soluble cellular antigens of nuclear or less commonly cytoplasmic origin. Some of the most common examples of systemic autoimmune disease are systemic lupus erythematosus (SLE), rheumatoid arthritis, scleroderma (and CREST), polymyositis, mixed connective tissue disease (MCTD), drug-induced SLE and Sjögren’s Syndrome.

HML’s ANA screen with reflex to individual autoantibodies is designed to aid in the diagnosis of many of the systemic autoimmune disorders. It may assist in the detection and identification of many autoantibodies to a number of nuclear and cytoplasmic cellular constituents. The table below shows the relationship between autoantibody and disease state for some of the most common systemic autoimmune disorders.


Disease Association (antibody prevalence)

SSA (Ro)

SLE (25-35%)

Sjögren’s syndrome (40-70%)

Neonatal Lupus (100%)

SSB (La)

Sjögren’s syndrome (30%),

SLE (10%)


SLE (15-30%, highly specific)


Mixed connective tissue disease (MCTD) (95%)


Scleroderma (20-35%)


Myositis (20-40%)

Centromere B

Scleroderma CREST variant (calcinosis)


esophageal dysmotility

sclerodactyly and telangiectasia


Drug-induced SLE (50%)


SLE (90% drug-induced lupus)

Although the exact etiology of autoimmune diseases is unknown, and the specific role played by autoantibodies in the onset of various autoimmune diseases is obscure, the association and frequency of detection of these autoantibodies, particularly of the IgG class by HML’s ANA test system, offers an efficient test procedure for the laboratory workup of patients with suspected systemic autoimmune disorders.

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