Autoimmune diseases (AID) are notoriously difficult to diagnose—and laboratory testing is crucial to the process. Anti-nuclear antibodies (ANA) in particular are hallmarks of many AID. In a recent review article, co-authors Kun-Young Sohn, MD, PhD, and Waliul I. Khan, MBBS, PhD, FRCPath, discuss both traditional and emerging methods for detecting ANA.
Today’s gold standard indirect immunofluorescence (IIF) detects a large number of autoantibodies that bind to a variety of nuclear antigens and is highly sensitive. However, it has a high false-positive rate, and is time-consuming, laborious, and frequently yields discrepant inter-laboratory results. Moreover, IIF requires highly trained personnel and is hard to standardize because of the subjectivity of interpretation.
Positive IIF results lead to further investigations using enzyme immunoassay (ELISA) to detect specific markers. ELISA offers the advantages of being automated and involving fewer subjective measurements. On the other hand, ELISAs have substrate differences, detect different isotypes, and have different antibody affinities. ELISA also requires multiple assays for different antibodies.
Newer multiplex immunoassays―either planar array or microbead―facilitate simultaneous quantification of multiple assays, and they represent a reaal improvement in the diagnostic power of ANA testing. Multiplex immunoassays also have good concordance with traditional methods while also providing rapid, sensitive, and specific results.
Sohn and Khan relay their experiences with and review the scientific literature involving multiplex immunoassays for ANA testing. One issue the authors faced was winning physicians over to a new style of reporting, as well as the analytical process itself. Based on their experiences, they conclude that significant cost savings and improved quality could accrue to labs with a large daily volume of samples that adopt multiplex immunoassay testing. “The physician receives results faster and gets the results of additional antibodies compared to the conventional ELISA method,” they write.
More on ANA testing to detect AID is available in the June issue of CLN.