Session: SUN 50-71-HPA Axis
Poster Board SUN-64
Authors: Veronica Ramirez, MD, Renee Kinman, MD, PhD, University of California San Francisco-Fresno Department of Pediatrics
Financial Disclosures: None
Purpose of Study
ACTH insufficiency is a life-threatening condition; however, testing for this diagnosis remains problematic. Although the insulin tolerance test is the gold standard to assess the hypothalamic-pituitary-adrenal (HPA) axis, risks include hypoglycemia and death. It is thus contraindicated in infants and not recommended as a routine diagnostic test in children. Alternative test methods include low-dose (LDT, 1 mcg) and standard-dose (SDT, 250 mcg) ACTH stimulation tests. Although LDT is thought to be more sensitive than SDT in detecting ACTH insufficiency, LDT can yield false positive results leading to life-changing implications for the patient. Problems inherent with LDT include the very low dose used and individual variations in timing of the cortisol peak after stimulation. This study was thus performed to determine if addition of 2 extra sampling times would help eliminate false positive results and thus unnecessary treatment.
All patients undergoing low-dose ACTH stimulation testing in the Children's Hospital Central California Endocrine Clinic were included. 102 fasting subjects (0.5 to 20 years old) underwent 114 tests over 20 months. 1 mcg Cortrosyn (ACTH) was diluted by the pharmacy and given intravenously followed by 5-10 ml of saline. Cortisol levels were collected at baseline, and 20, 30, 40, and 60 minutes following Cortrosyn administration.
Summary of Results
26 patients (23%) were diagnosed with ACTH insufficiency as a result of the test. Although 50% of females and 35% of males obtained peak cortisol levels 40 min after ACTH administration, only 3 patients (2.6%) would have had a false positive test without the addition of 20 and 40 min sampling times.
Adding 20 and 40 min sampling times to a low-dose ACTH stimulation test identified a 2.6% false positive rate. Although this rate is small, these additional time points should be considered to avoid unnecessary treatment. However, attention also needs to be paid to other factors that can result in a false positive diagnosis, including ensuring a fasting study, early morning testing, and pharmacist-assisted dilution of the ACTH dose with a normal saline bolus immediately following ACTH injection to ensure complete administration of dose. Given the high number of positive tests, further consideration needs to be given regarding the risks and benefits of performing a low dose ACTH stimulation test to test the HPA axis if a failed test will result in lifelong glucocorticoid therapy.
Nothing to Disclose: VR, RAK
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