Commercial Tests for Scleroderma May Miss Subsets

The immunofluorescence antinuclear antibody (IF-ANA) test is recommended to help detect the presence of scleroderma specific antinuclear antibodies.

Finding the antibodies is a helpful predictor of disease manifestations, clinical course, and outcome in scleroderma. However, many commercial laboratories have recently adopted a newer, automated method that use nonimmunofluorescence antinuclear antibody testing (NEW ANA).

In a study carried out at Georgetown University Medical Center, (GUMC; Washington DC, USA), scientists evaluated all test results performed through commercial laboratories of more than 200 scleroderma patients treated in the Georgetown scleroderma clinic between June 2008 and June 2009. Test results using NEW ANA were available in 58 scleroderma patients. Twenty-eight patients (48%) tested negative. Of these 28 patients, 22 had either positive results using IF-ANA or one of the scleroderma specific antibodies.

NEW ANA test results were not available for the remaining 183 scleroderma patients. The IF-ANA testing was conducted in these patients and the positive antibody results were divided by subtypes. The NEW ANA testing, that is the ANA test without immunofluorescence, failed to identify patients with a particular subset of scleroderma specific antinuclear antibodies and other patterns that are picked up with IF ANA testing.

Scleroderma is a chronic systemic autoimmune disease characterized by fibrosis (or hardening), vascular alterations, and autoantibodies. There are two major forms: Limited systemic sclerosis/scleroderma cutaneous manifestations mainly affecting the hands, arms and face; and diffuse systemic sclerosis/scleroderma, which rapidly progresses and affects a large area of the skin and one or more internal organs, frequently the kidneys, esophagus, heart and lungs.

Victoria K Shanmugam, MBBS, M.R.C.P., an assistant professor at GUMC, said, "Given what we know about the subsets that are not detected by the NEW ANA testing, it appears that as many as 40% of the scleroderma patients would have tested negative using the new commercial testing method. If a clinician has clinical suspicion for scleroderma, they should order the immunofluorescent ANA.” The results of the study were presented at Annual Scientific Meeting of the American College of Rheumatology in Atlanta, GA, USA, on November 10, 2010.

Related Links:
Georgetown University Medical Center
American College of Rheumatology