International survey on high- and low-dose synacthen test and assessment of accuracy in preparing low-dose synacthen.

OBJECTIVE: The short synacthen test (SST) is widely used to assess patients for adrenal insufficiency, but the frequency and protocols used across different centres for the low-dose test (LDT) are unknown. This study aimed to survey centres and test the accuracy of ten different synacthen preparation strategies used for the LDT. METHODS: Members of 6 international endocrine societies were surveyed regarding diagnostic tests used for adrenal insufficiency, and in particular the SST. Synacthen was diluted for the LDT and concentrations measured using a synacthen ELISA. RESULTS: Survey responses were received from 766 individuals across 60 countries (52% adult, 45% paediatric endocrinologists). The SST is used by 98% of centres: 92% using high-dose (250 µg), 43% low-dose and 37% both. Ten low-dose dilution methods were assessed and variation in synacthen concentration was demonstrated with intramethod coefficients of variation (CV) ranging from 2.1% to 109%. The method using 5% dextrose as a diluent was the least variable (CV of 2.1%). The variation in dilution methods means that the dose of synacthen administered in a LDT may vary between 0.16 and 0.81 µg. CONCLUSIONS: The high-dose SST is the most popular diagnostic test of adrenal insufficiency, but up to 72% of paediatric endocrinologists use a LDT. There is considerable variation observed both within and between low-dose synacthen dilution methods creating considerable risk of inaccurate dosing and thereby invalid results.

Use of salivary cortisol and cortisone in the high- and low-dose synacthen test.

CONTEXT: Salivary cortisone reflects serum cortisol levels, is more sensitive than salivary cortisol at lower values of serum cortisol and is noninvasive. OBJECTIVE: To investigate the relationship between serum cortisol and salivary cortisol and cortisone following low- and high-dose synacthen. DESIGN AND SETTING: Prospective pharmacodynamic studies in clinical research facilities. PARTICIPANTS AND INTERVENTION: Thirty-five dexamethasone-suppressed, healthy adult males underwent an intravenous synacthen test: N = 23 low-dose (1 mcg), N = 12 high-dose (250 mcg). Paired serum and salivary samples were taken at 15 sampling points over 120 minutes. MAIN OUTCOME MEASURE: Serum cortisol and salivary cortisol and cortisone were analysed for correlations and by a mixed-effects model. RESULTS: At baseline, the correlation between serum cortisol and salivary cortisol was weak with many samples undetectable (r = .45, NS), but there was a strong correlation with salivary cortisone (r = .94, P < .001). Up to 50 minutes following synacthen, the correlation coefficient between serum cortisol and salivary cortisol and cortisone was <0.8, but both had a stronger correlation at 60 minutes (salivary cortisol r = .89, P < .001, salivary cortisone r = .85, P < .001). The relationship was examined excluding samples in the dynamic phase (baseline to 60 minutes). Salivary cortisol and cortisone showed a close relationship to serum cortisol. Salivary cortisone showed the stronger correlation: salivary cortisol r = .82, P < .001, salivary cortisone r = .96, P < .001. CONCLUSION: Following synacthen, both salivary cortisol and cortisone reflect serum cortisol levels, but there is a lag in their rise up to 60 minutes. The results support further research for possible future use of a 60-minute salivary cortisone measurement during the synacthen test.