Anti–double-stranded DNA assays
Recent findings also raise questions about the use of assays that specifically assess for anti–double-stranded DNA (anti-dsDNA) antibodies, which are highly associated with SLE and have been used as a biomarker for the disease, Dr. Pisetsky said.
For example, a comparison of two anti-dsDNA assays showed discordant results with respect to negativity for anti-dsDNA antibodies in 64 of 181 samples from SLE patients. One assay showed a 70.7% rate of anti-dsDNA negativity and the other showed a 37.6% rate.
The concern regarding test variability relates to the issue of ANA positivity and eligibility for study enrollment and certain treatments; test variability can affect the diagnosis of patients with SLE because ANA positivity is an important finding in routine clinical care, and for anti-dsDNA, test variability can affect assessment of disease activity, he explained.
Tests may differ in a number of ways, such as in their specificity, sensitivity, avidity, and range of epitopes detected. Unfortunately, not enough is known at this point to make specific recommendations regarding best test kits, and while there are alternative technologies that could be useful for ANA testing, none has been validated for particular use in the assessment of trial eligibility, Dr. Pisetsky said.
Nonetheless, awareness of the test variability is important, especially when it comes to assessing patients for trial eligibility and prescribing medications, he added. “For practical, real-world utilization, people need to know about this.”
Dr. Pisetsky reported receiving ANA-related research support from Pfizer, conducting collaborative research with Bio-Rad and EuroImmun, and serving as an adviser to ImmunArray.