Predictiong the result of 250 µg ACTH stimulation test by the morning cortisol level.

Abstract

Background and Aims: Morning cortisol level is the test for diagnosis of adrenal insufficiency(AI). When the result of morning cortisol level was inconclusive, the 250 µg ACTH stimulation test was used. However the correlation between the morning cortisol and the cortisol response in the ACTH stimulation test has not been studied. So we studied to find out the morning cortisol level that could predict the result of ACTH stimulation test.

Material and methods : This study was retrospective descriptive study. All adult patients who were performed ACTH stimulation test in Prapokklao hospital from June 2006 through october 2008 were recruited. The correlation between the morning cortisol and the results of the ACTH stimulation test were determined.The ROC curve was used to find out the best morning cortisol level for the highest sensitivity and specificity of the ACTH stimulation test.

Results : One hundred and seventy-seven ACTH stimulation tests were done during that time. There were 135 morning cortisol levels which were inconclusive (3-18 mg/dl). The morning cortisol levels were highly correlated to the peak cortisol responses after the ACTH stimulation test. The morning cortisol levels which were below 8.25mg/dl can predict the negative result of the response after the ACTH stimulation test
(peak cortisol level ? 18 mg/dl) with 78.8% of sensitivity , 80% of specificity, 73.24% of positive predictive value and 84.62% of negative predictive value (AUC=0.854). The factors which correlated to the cortisol levels after ACTH stimulation test were the history of steroid usage (P<0.001),cushingoid appearance (P<0.001) and eosinophilia (P=0.002).

Conclusions: The morning cortisol level which was below 8.25mg/dl was the predictive negative result of the response after the ACTH stimulation test, especially in patient who had the history of chronic steroid usage, cushingoid appearance and eosinophilia.

Key word : ACTH Stimulation test, Adrenal insufficiency, morning cortisol level,Diagnosis