Investigation of appropriate limit value for low dose dexamethasone suppression test applied as screening test in patients followed with the diagnosis of chronic renal failure

Objective : Chronic renal failure (CRF) is the cause of false positivity for the Overnight 1 mg Dexamethasone Suppression Test (1 mg DST). As the reason for this in studies; Various reasons such as variability in dexamethasone bioavailability, increased basal cortisol release and disruption of diurnal rhythm, and imbalance in free and bound cortisol levels due to decrease in protein levels have been suggested in CRF patients. In this study, it was aimed to determine a specific cut-off value for 1mg DST to prevent false positivity seen with the standard cut-off value in CRF patients. Material and methods: The data of 1038 patients who applied to our hospital's endocrinology outpatient clinic between January 01, 2018 and December 31, 2019 and who were asked for 1 mg Dexamethasone Suppression Test (DST) were retrospectively scanned from the hospital information and management system. The patients were divided into 4 groups according to their glomerular filtration rates (GFR). Difference between 1 mg DST hydrangeas and Pseudocushing Syndrome among the groups was examined. ROC analysis was applied to determine the new limit value for the group with a difference. Results : In patients classified under Group IV with a GFR below 30 ml / min / 1.73m2, both 1 mg DST median and Pseudocushing Syndrome incidence were significantly higher than other groups. As a result of ROC Analysis applied to these patients, the new limit value was found to be 3.2 mcg / dl with 100% Sensitivity and 92% specificity. Conclusion : This study is the first study to determine limit values at 1 mg DST for CKD patients. However, in order to increase the accuracy of the analysis, ROC analysis should be applied to those who are compatible with Pseudocushing Syndrome by performing this study in more hemodialysis patients. Key words : DST, CRF, limit value, ROC analysis