Session: SUN 410-423-Hypothalamic-Pituitary-Adrenal Axis (posters)
Poster Board SUN 420
Aim: We conducted a prospective trial comparing the cortisol responses to three different cosyntropin doses with that to ITT. We compared the diagnostic characteristics of 1μg IV (LDCT), 25μg IM (MDCT), and 250μg IM (SDCT) for evaluating secondary adrenal insufficiency (SAI) using ITT as the gold standard. We assessed the best total and free cortisol cut-off during the CSTs and ITT.
Method:The study consisted of adult patients with hypothalamic/pituitary disease (G1, n=10) with at least one pituitary axis deficiency other than ACTH deficiency and healthy volunteers (G2, n=12). Cortisol levels were measured at 30 and 60 minute (min) during CSTs. All tests were done in random order and separated 2 - 90 days from each other. None of the women were on estrogen. None of the patients had pituitary surgery within six weeks prior to enrollment. A peak cortisol cut-off of 18 μg/dl was the accepted normal response to ITT. Sensitivity (SE) and Specificity (SP) were calculated for different total and free cortisol cut-offs during CSTs. Correlations of peak levels were compared with those in ITT. The diagnostic ability of each test was evaluated using ROC analysis. Total and free cortisol levels were measured by liquid chromatography and mass spectrometry, respectively.
Results:The median (range) age and F/M sex ratio for G1 and G2 were 54 (23-62), 2/8 and 33 (21-51), 6/6, respectively. The best total cortisol cut-offs for diagnosis of SAI were 14.6 μg/dl (100% SE & SP) for LDCT, 18.7 μg/dl (100% SE, 88% SP) for MDCT, 16.1 μg/dl (100% SE & SP) for 30 min SDCT and 19.5 μg/dl (100% SE & SP) for 60 min SDCT. There was no difference in the ROC curve for cortisol values between the CSTs (p>0.41). Using a cortisol cut-off of 18 μg/dl as the pass criteria on CSTs, only cortisol level at 30 min on SDCT provided perfect discrimination based on ITT.
All subjects had peak total cortisol at 60 min on the SDCT. On MDCT and LDCT, 81% and 50% of subjects, respectively, had peak cortisol at 30 min. Peak cortisol level on SDCT correlated better with ITT compared to MDCT (p=0.044). Among CSTs, LDCT had the lowest correlation with ITT.
The best peak free cortisol cut-offs were 1 μg/dl for ITT, 0.9 μg/dl for LDCT, 0.9 μg/dl for MDCT, and 0.9 μg/dl and 1.3 μg/dl for 30 min and 60 min SDCT respectively.
Conclusion: All CSTs had excellent correlations with ITT. This pilot study does not suggest an advantage in using 25 µg cosyntropin dose during the CST. A free cortisol cut-off of 1 μg/dl may be used as the pass criteria during LDCT, MDCT, 30 min SDCT, and ITT. Larger cohort is needed to confirm this cut-off level.
Disclosure: NJC: Employee, Quest Diagnostics. MJM: Medical Director, Quest Diagnostics Inc.. RER: Collaborator, None. Nothing to Disclose: SVP, JB, LK, AHH
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