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 is used to detect the presence of Jo-1 antibodies in the blood, which are most commonly associated with polymyositis and dermatomyositis, two types of autoimmune inflammatory muscle diseases. These antibodies target a specific protein involved in protein synthesis within cells. A positive Jo-1 antibody test can help confirm the diagnosis of these conditions and may also indicate an increased risk for complications, such as interstitial lung disease, which often occurs alongside these diseases. While a negative result typically suggests that these conditions are less likely, it doesn't rule them out entirely. Additional tests may be needed to confirm a diagnosis or explore other possible autoimmune conditions.

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 detects antibodies against the centromere, a part of the chromosome involved in cell division. These antibodies are most commonly associated with a condition called Limited Systemic Sclerosis (also known as CREST syndrome), a form of scleroderma that affects the skin and internal organs. A positive result for centromere antibodies is often used to help diagnose CREST syndrome and assess the likelihood of related complications. While a negative result suggests that this condition is less likely, it does not completely rule it out. Additional tests may be needed to confirm a diagnosis or explore other possible autoimmune conditions.

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.