Use of the low-dose corticotropin stimulation test for the diagnosis of secondary adrenocortical insufficiency.

OBJECTIVE To assess the clinical utility and safety of the low-dose corticotropin stimulation test in the diagnosis of secondary adrenocortical insufficiency. DESIGN Prospective study. SETTING Regional hospital, Hong Kong. PARTICIPANTS Seventy-two Chinese patients with suspected secondary adrenocortical insufficiency. MAIN OUTCOME MEASURE Serum cortisol response during the low-dose corticotropin stimulation test, using the insulin tolerance test as the gold standard. RESULTS The 30-minute cortisol level during the low-dose corticotropin stimulation test was most closely correlated (r=0.79) with the peak cortisol level achieved during the insulin tolerance test. The optimum sensitivity and specificity of the low-dose corticotropin stimulation test were obtained at a cut-off value of 550 nmol/L or more for the 30-minute cortisol level. Using the insulin tolerance test as the gold standard for comparison, the low-dose corticotropin stimulation test had a sensitivity of 97%, a specificity of 78%, a positive predictive value of 81%, and a negative predictive value of 97% at this cut-off value. The positive likelihood ratio was 4.4 and the negative likelihood ratio 0.04. CONCLUSION The low-dose corticotropin stimulation test, using the cortisol response at 30 minutes after synacthen 1 microg is a safe, convenient, and sensitive method for screening abnormalities of the hypothalamic-pituitary-adrenocortical axis in Chinese patients suspected of having secondary adrenocortical insufficiency.