Question:

When my blood was tested for ANA, which always has a low positive, they also did a panel for other more specific antibodies. I tested positive for SCL-70. However, I have none of the obvious symptoms of scleroderma. My doctor said that this is the fifth or sixth time in the past year that this particular labrotory has given him a positive SCL-70 for someone who had no obvious symptoms of scleroderma, and so he thinks it is likely a false positive. Are false positives common? If the test was not a false positive, do I definitely have scleroderma, perhaps “sine scleroderma”? Or, can the antibody show up before the symptoms do, and I will likely develop scleroderma later? Or, can you have a positive SCL-70 and never get scleroderma? Thank you so much for your expert opinion.

Answer:

The Scl-70 antibody, also known as anti-topoisomerase antibody, is a blood test that is most commonly associated with Systemic Sclerosis (SSc), also known as scleroderma. Scl-70 is present approximately 60% of the time in the diffuse variant of SSc and is present about 30% of the time in the limited variant of SSc.1 A review of literature by Drs. Reveille and Solomon in 2003 suggests that the Scl-70 antibody is relatively specific for scleroderma. However, it is still possible to have an elevated Scl-70 antibody and not have scleroderma. There is a small possibility that the laboratory is related to another connective tissue or even the benign, primary variant of Raynaud’s phenomenon (RP). RP is present in about 95% of individuals that have scleroderma. It certainly may precede other features of SSc, such as skin thickening, by several years.

References

1. Walker UA, et al. Clinical risk assessment of organ manifestations in systemic sclerosis: a report from the EULAR Scleroderma Trials and Research group database. Ann Rheum Dis 2007;66:754-763.
2. Reveille JD, Solomon DH. Evidence-based guidelines for the use of immunologic tests: anticentromere, Scl-70, and nucleolar antibodies. Arthritis Care & Research 2003;49:399-412.

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