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Scl-70 (anti-topoisomerase) Ab in serum

Indications: - evaluation of scleroderma - diffuse scleroderma (20-50%) Reference values: - Normal: Negative Interpretation: - <20 EU/mL: negative for antibodies to Scl-70 - 20-25 EU/mL: Equivocal for antibodies to Scl-70 - >25 EU/mL: positive for antibodies to Scl-70 Clinical significance: - 2 autoantibodies have been identified which are present almost exclusively in scleroderma - anti-Scl-70 antibody is found in 20-50% of patients with diffuse scleroderma - anti-Scl-70 Ab is directed against a 70kDa nuclear protein identified as topoisomerase 1 - more likely in scleroderma patients with pulmonary fibrosis [5] - anti-centromere antibody is strongly associated with limited scleroderma, or CREST syndrome - anti-centromere Ab is directed against the chromosomal kinetochore - detection of either of these 2 autoantibodies is highly is highly specific for scleroderma - because these 2 autoantibodies rarely occur in the same patient, they are useful in determining the scleroderma subtype, diffuse or limited (CREST syndrome) Principle: Scl-70 antigen is purified from calf thymus, bound to microwells and stabilized for extended shelf life. Diluted patient sera are placed in the microwells & incubated. If anti-Scl-70 antibodies are present, they will bind to the antigen in the microwell. After washing the microwells to remove residual sample, a second incubation with anti-human IgG conjugated to alkaline phosphatase is carried out. Conjugate will bind immunologically to the anti- scl-70 IgG of the antigen-antibody complex, forming a 'sandwich' consisting of: Conjugate (Enzyme-labeled Anti-human IgG) Human anti-Scl-70 (IgG) Well Coated with Scl-70 antigen Unbound conjugate is removed in the subsequent washing step. Enzyme substrate is then added to the microwell & if bound conjugate is present, the colorless substrate (p-nitrophenyl phosphate) will be hydrolyzed to form a yellow end product (p-nitrophenol). The intensity of the color is measured photometrically at 405 nm & is proportional to the concentration of anti-Scl-70 present in the patients sample. Specimen: Serum is separated from the clot & refrigerated, 2-8 degrees C for short term storage or stored frozen, -20 degrees C, for long term storage. Avoid freeze-thaw cycles. CAUTION: Serum samples should not be heat inactivated, as this may cause false positive results. No special patient preparation required.

Related

anti-Scl-70 (anti-topoisomerase) Scl-70 antigen

Specific

SCL-70 extractable nuclear IgG in serum

General

Scl-70 (anti-topoisomerase) Ab in body fluid

References

  1. Henry, John Bernard, Clinical Diagnosis amd Management by Laboratory Methods, W. B. Saunders Co., Philadelphia, 1991. pp 891-892.
  2. The Physicians Guide to ENA Testing, Diamedix Corporation, Miami, 1991. pp 1-8.
  3. Summary of Procedure. DiaMedix Corporation, Miami, Oct. 1991. pp 1-8.
  4. Poly-ENA Extractable Nuclear Antigen Assay for Detection of Antibodies to RNP, Sm, and/or SSA (RO), & SSB (LA). Zeus Scientific, Inc., Raritan, New Jersey, 1987. pp 1-5.
  5. Medical Knowledge Self Assessment Program (MKSAP) 14, 17. American College of Physicians, Philadelphia 2006, 2015

Component-of

extractable nuclear antigen (ENA) Ab