Study results mean “you can’t make broad statements about ANA results because the kits are behaving so differently,” he says. “There are other assay formats available, including ELISA and multiplex, and, in the context of a clinical trial, if the presence of ANA is a determinant of eligibility, the company doing the study may want to do more than one test to screen patients. In the regular world of practice, there’s a balancing act that has to go on.”
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Clinicians must balance their knowledge of testing protocols with their need to properly diagnose and treat their patients. IFAs are not simple tests—they are time consuming, results can be subjective, reproducibility can be limited, and they aren’t easily automated, Dr. Pisetsky says. In comparison, the ELISA and the multiplex assays are easier to perform in the laboratory. Still, no test is perfect, and it’s up to the provider to determine which test is the most appropriate given the particular patient’s situation. The IFA is still considered the gold-standard for ANA testing, despite the variability in the test kits.
“There are two approaches,” Dr. Pisetsky says. “One is to use the ELISA or multiplex for screening and then confirm it with IFA. Other people recommend the other direction: IFA first, and then do the multiplex to figure out which antibodies are present.”
Kimberly J. Retzlaff is a freelance medical journalist based in Denver.
- Pisetsky DS, Spencer DM, Lipsky PE, Rovin BH. Assay variation in the detection of antinuclear antibodies in the sera of patients with established SLE. Ann Rheum Dis. 2018 Jun;77(6):911–913.