Novel Bioassay Developed to Determine Glucocorticoid Sensitivity

Glucocorticoids (GCs) remain the first line treatment for almost all non-infectious inflammatory diseases, ranging from acute asthma to rheumatoid arthritis. However, across all conditions, patients have a variable response to GCs with approximately 30% being non-responders.

There is a pressing clinical need for a predictive biomarker of GC responsiveness and the availability of such a tool would also enable patient stratification for the conduct of smart clinical trials in GC resistance. Lymphocyte GC sensitivity has been shown to be closely associated with clinical GC sensitivity in a number of inflammatory diseases.

Clinical scientists at the University of Bristol took peripheral blood samples from healthy subjects by standard venipuncture into EDTA collection tubes. Peripheral blood monocytes were isolated by density gradient centrifugation using Leucosep tubes and cell viability assessed by Trypan blue exclusion. Cells were counted manually by light microscopy using a hemocytometer.

Dexamethasone inhibition of lymphocyte proliferation assays (DILPA) were performed and plates were harvested onto glass fiber filter paper using a Skatron cell harvester. The scientists then optimized and validated a novel non-radioactive in vitro bioassay based on measuring cellular proliferation by incorporation of bromodeoxyuridine (BrdU), termed the BrdU incorporation in lymphocyte steroid sensitivity assay (BLISS). The novel BLISS assay to determine GC sensitivity had a suitably high area under receiver operating characteristic (AUROC, 0.82) and sensitivity in correctly identifying GC non-responders (83%) in reference to the existing gold standard lymphocyte GC sensitivity assessment method (DILPA). The sensitivity of BLISS in identifying GC non-responders is the most important measure of diagnostic accuracy; it must correctly identify those patients who do not respond to GCs so as to reliably reduce their unnecessary exposure to GCs and guide alternative management.

The authors concluded that they had validated a simple novel bioassay with a standardized laboratory protocol, which accurately measures GC sensitivity. This has broad translational implications and could be applied to many inflammatory diseases to guide clinical management of individual patients, ensuring that GC responsive patients are correctly treated with GCs while reducing unnecessary exposure to GCs and accelerating the appropriate escalation of treatment of GC resistant patients. The study was published on December 15, 2016, in the journal Biomarker Research.