Eosinophilic granulomatosis with polyangiitis (EGPA) is a disease that can be hard to manage. Certain blood tests (also known as biomarkers) have been used to follow disease activity and predict relapse. How well these markers actually work in patients hasn’t been rigorously tested.
Paul A. Monach, MD, from the section of Rheumatology at the Boston University School of Medicine, and others studied the performance characteristics of absolute eosinophil counts (AEC), IgE antibodies in the blood, erythrocyte sedimentation rates (ESR), and C-reactive protein (CRP). The research was published in the November 2014 edition of Rheumatology.
Lacking Indicators of What to do Next
“We have all these tests that help tell us a person has the disease,” said Dr. Monach. “What we are lacking now are indicators that suggest what we should do next. It is hard to know when a person needs their medications changed or if we can safely decrease them.”
Patients were enrolled from the Vasculitis Clinical Research Consortium (VCRC) Longitudinal Study of EGPA, an observational group composed of people from North America. The patients are seen at eight centers specializing in vasculitis.
They underwent a standardized clinical assessment that included obtaining the biomarkers. Their physicians also recorded information on treatment status and medications they were prescribed. The visits were scheduled either quarterly, annually, or as need for disease flare-ups.
Seventy-four percent of the 892 visits by 141 patients took place while they were on treatment. Most of them were deemed to be in remission or having only mild disease activity. Correlation between the various biomarkers and disease state were either very low or not significant. They found a few weak correlations between disease activity and eosinophil count. ESR and AEC were able to weakly predict flares.
Results Show No Clinical Significance
The results have shown some statistically significant associations with active disease based on the expert opinion of the doctors. But they found no clinical significance. There were differences in test results, but not enough of a difference in outcomes to reliably guide treatment decisions.
“We always talk to our patients about how they are feeling and use our clinical experience in making treatment decisions,” said Dr. Monach. “We are doing these tests already and assume they are good, but they aren’t. This doesn’t mean we shouldn’t do them, but just take them with a big grain of salt.”
Patients Should Know Limits
Those being treated for EGPA should also realize the limitations of the biomarkers in their treatment.
“Some get really caught up in their AEC or other lab values and become worried that they are going to be sick,” noted Dr. Monach. “Patients shouldn’t focus on these numbers alone. How they feel is a much better guide to treatment and their disease state.”
Value of commonly measured laboratory tests as biomarkers of disease activity and predictors of relapse in eosinophilic granulomatosis with polyangiitis.
Grayson PC, Monach PA, Pagnoux C, Cuthbertson D, Carette S, Hoffman GS, Khalidi NA, Koening CL, Langford CA, Maksimowicz-McKinnon K, Seo P, Specks U, Ytterberg SR, Merkel PA; Vasculitis Clinical Research Consortium.
Rheumatology (Oxford). 2015 Aug;54(8):1351-9. doi: 10.1093/rheumatology/keu427.
By Kurt Ullman, RN