LBODP082 Thresholds For Normal In Low Dose Cortrosyn Stimulation Depends On Assay Type

Stimulation testing is used to diagnose adrenal insufficiency. The low dose stimulation test uses Cosyntropin 1 mcg to measure cortisol when pituitary disease is suspected. Protocols call for cortisol levels at baseline, 30, and 60 minutes post-administration. A passing peak cortisol threshold of 18 mcg/dl is often used. In 2019, most cortisol assays in our area shifted to more sensitive methods; these are reported to require a lower pass threshold of 12 -14 mcg/dl. We did a retrospective review on 186 consecutive patients in whom newer assays were used, to describe pass/fail rates by timepoint/threshold. Using newer assays, and cortisol cut-off of 14 mcg/dl, a significantly higher percentage pass than if one used newer assays with the older cut-off of 18 mcg/dl (84.9% vs 72%.). When a cut-off of 14 is used, a 60 min assay adds little (pass rate including only 0 and 30 min values =83.3%; pass rate if include 0, 30, and 60 min values = 84.9%). We suggest that with newer assays, interpreting with a 14 mcg/dl cut-off shows higher pass rate than with 18 mcg/dl cut-off. We also suggest that when using newer assays and cut-off of 14 mcg/dl, 60 min assays add little. Presentation: No date and time listed