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Test Code SCL70 Scl 70 Antibodies, IgG, Serum

Important Note

ASANTE order code: SCLAB

Epic/Beaker code is LAB5167

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

Scl 70 Ab, IgG, S

Specimen Type

Serum


Specimen Required


Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL


Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild OK; Gross reject

Icterus

Mild OK; Gross OK

Other

NA

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 21 days
  Frozen  21 days

Specimen Minimum Volume

0.4 mL

Day(s) and Time(s) Performed

Monday through Saturday; 4 p.m., Sunday; 11a.m.

Specimen Retention Time

7 days

Analytic Time

1 day

Reference Values

<1.0 U (negative)

≥1.0 U (positive)

Reference values apply to all ages.

Useful For

Evaluating patients with signs and symptoms of scleroderma and other connective tissue diseases in whom the test for antinuclear antibodies is positive

Testing Algorithm

See Connective Tissue Disease Cascade (CTDC) in Special Instructions.

Method Name

Multiplex Flow Immunoassay

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

86235

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SCL70 Scl 70 Ab, IgG, S 47322-3

 

Result ID Test Result Name Result LOINC Value
SCL70 Scl 70 Ab, IgG, S 47322-3

Clinical Information

Scl 70 (topoisomerase 1) is a 100-kD nuclear and nucleolar enzyme. Scl 70 antibodies are considered to be specific for scleroderma (systemic sclerosis) and are found in up to 60% of patients with this connective tissue disease. Scl 70 antibodies are more common in patients with extensive cutaneous involvement and interstitial pulmonary fibrosis, and are considered a poor prognostic sign.(1,2)

 

See Connective Tissue Disease Cascade (CTDC) in Special Instructions.

Interpretation

A positive test result for Scl 70 antibodies is consistent with a diagnosis of scleroderma.

Cautions

Testing for Scl 70 antibodies is not useful in patients without demonstrable antinuclear antibodies.

Clinical Reference

1. Homburger H, Larsen S: Detection of specific antibodies. In Clinical Immunology: Principles and Practice. First edition. Edited by R Rich, T Fleisher, B Schwartz, et al. St. Louis, Mosby-Year Book, Inc, 1996, pp 2096-2109

2. White B: Systemic sclerosis. In Clinical Immunology Principles and Practice. Second edition. Edited by R Rich, T Fleisher, W Shearer, et al. St. Louis, Mosby-Year Book, 2001, pp 64.1-64.10

Method Description

Recombinant Scl 70 antigen is bound to polystyrene microspheres, which are impregnated with fluorescent dyes to create a unique fluorescent signature. Scl 70 antibodies, if present in diluted serum, bind to the Scl 70 antigen on the microspheres. The microspheres are washed to remove extraneous serum proteins. Phycoerythrin (PE)-conjugated antihuman IgG antibody is then added to detect IgG anti-Scl 70 bound to the microspheres. The microspheres are washed to remove unbound conjugate, and bound conjugate is detected by laser photometry. A primary laser reveals the fluorescent signature of each microsphere to distinguish it from microspheres that are labeled with other antigens, and a secondary laser reveals the level of PE fluorescence associated with each microsphere. Results are calculated by comparing median fluorescence response for Scl 70 microspheres to a 4-point calibration curve.(Package insert: Bioplex 2200 ANA Screen. Bio-Rad Laboratories, Hercules, CA)