Serum cortisol level to screen for significant hypothalamic-pituitary-adrenal axis suppression in patients receiving multiple steroid injections

Background Morning serum cortisol level (mSCL) is a practical screening tool for hypothalamic-pituitary-adrenal (HPA) axis suppression and has been used to assess for duration of cortisol deficiency after epidural and peripheral glucocorticoid injections. More evidence is needed to establish the utility of mSCL in patients undergoing repeat injections with increasing cumulative glucocorticoid equivalent dose (CGED) that could place them at higher risk of HPA axis suppression.Objectives To estimate the prevalence of spine injection candidates with significant HPA axis suppression (sigAS), to understand the correlation between 12 months of CGED and the presence of sigAS based on the timing of mSCL collection after the most recent glucocorticoid injection (within 6 weeks or between 6 weeks and 12 months), and to investigate demographic and clinical factors relating to sigAS.Methods Retrospective chart review of patients scheduled for spine injection who had an associated mSCL and documented histories of prior glucocorticoid injections. The steroid name, dose, type, and procedure location were recorded for each injection that occurred within 12 months before mSCL. CGED was calculated from standard glucocorticoid equivalent conversion factors.Results SigAS was present in 7.8% to 22% of the analysis cohorts. There was no association found between CGED and sigAS regardless of timing of mSCL. There was a trend toward lower mSCL and sigAS with increasing CGED. There were no significant relationships found between sigAS and overall demographic or clinical factors.Conclusions A 3-fold reduction in the rate of sigAS was noted 6 weeks after the most recent steroid injection. Using mSCL provides a template to investigate the impact of CGED and the best timing for mSCL collection in order to define a more practical guideline to identify patients at higher risk of sigAS earlier and plan for future spine injections.