Extractable Nuclear Antigens (ENA) Profile, Quantitative

The Scl-70 Antibody test detects anti-topoisomerase I antibodies in the blood. These autoantibodies target topoisomerase I, an enzyme essential for unwinding DNA during cell replication. Their presence indicates an autoimmune reaction, where the immune system mistakenly attacks the body’s own tissues.

SCL-70 antibodies are found in about 40% of patients with progressive systemic sclerosis (PSS). A positive result suggests a higher likelihood of systemic sclerosis, particularly the diffuse cutaneous type, which is more often associated with lung and internal organ involvement. However, not all patients with systemic sclerosis test positive for SCL-70 antibodies, and in some cases, these antibodies may also appear in other connective tissue diseases. A negative result does not rule out systemic sclerosis but makes the diagnosis less likely. Results must always be interpreted in combination with symptoms, physical findings, and other laboratory and imaging studies, not standalone. 

The SSA - RO (Soluble Substance A)- IgG antibody is a blood test that detects IgG autoantibodies that react against SS-A (Ro) antigens. A positive result suggests an autoimmune response and helps confirm disorders such as lupus or Sjögren’s syndrome.

The SSB - LA (Soluble Substance B) - IgG antibody is a blood test that detects IgG autoantibodies that react against the SS-B (La) antigen. A positive result indicates an autoimmune response and helps support the diagnosis of disorders such as lupus or Sjögren’s syndrome.

The Jo-1 antibody test detects autoantibodies against histidyl-tRNA synthetase, an enzyme essential for protein synthesis inside cells. The presence of these antibodies indicates an autoimmune reaction in which the immune system mistakenly attacks muscle and connective tissues.

Jo-1 antibodies are present in approximately 20–30% of patients with polymyositis or dermatomyositis and are considered highly specific for these conditions. Their presence is often associated with interstitial lung disease, arthritis, Raynaud’s phenomenon, and mechanic’s hands.

A positive result suggests a higher probability of inflammatory myopathies, especially when accompanied by respiratory symptoms or muscle weakness. However, a negative result does not completely rule out polymyositis or dermatomyositis, as not all patients with these conditions have Jo-1 antibodies. Results should always be interpreted alongside clinical symptoms, physical examination, imaging, and other laboratory investigations.

The Sm Antibody Smith Antibody Serum test detects the presence of antibodies against the Smith antigen, a protein found in the nucleus of cells. These antibodies are most commonly associated with systemic lupus erythematosus (SLE), an autoimmune disease where the immune system attacks healthy tissues. A positive result for Sm antibodies is highly specific for SLE and can help confirm the diagnosis, especially when combined with other clinical findings. A negative result does not rule out lupus entirely, as some people with SLE may not have these antibodies. Additional tests may be needed to confirm a diagnosis or explore other possible autoimmune conditions.

The Centromere Antibody test measures the presence and level of antibodies that target centromere proteins in the blood. Centromeres are structures within chromosomes that play a key role in cell division. When the immune system mistakenly produces antibodies against these proteins, it can lead to autoimmune reactions affecting connective tissues, blood vessels, and internal organs.

High levels of centromere antibodies are strongly associated with limited systemic sclerosis (CREST syndrome), while low or absent levels are usually seen in healthy individuals or those with other autoimmune conditions. Detecting these antibodies helps clinicians confirm a diagnosis, assess disease severity, and monitor potential complications over time.

The U1-SnRNP (68 KDa) - IgG antibody test measures the presence of autoantibodies against the 68 KDa protein of the U1 small nuclear ribonucleoprotein (snRNP) complex in the blood. These antibodies indicate an abnormal immune response, where the body’s immune system mistakenly targets its own cells.

High levels of U1-SnRNP (68 KDa) antibodies are often seen in patients with mixed connective tissue disease (MCTD) and may also be present in systemic lupus erythematosus (SLE). Detecting these antibodies supports diagnosis and differentiation between different autoimmune disorders and guiding appropriate treatment. Low or absent levels are generally considered normal but must be interpreted in conjunction with other clinical findings and laboratory tests.