Outpatient synacthen testing in a large metropolitan region: a clinical audit.

Aim: To audit short synacthen tests (SSTs) performed at a single laboratory within the greater Auckland area.

Methods: Two hundred and eighty-seven SSTs conducted in 286 individuals between September 2016 and September 2019 were assessed. Test requests were not triaged. We assessed source of referrals, indications for testing, adequacy of pre-test information and test outcomes.

Results: Seventy-one percent of referrals were for women. Fifty-six percent were from primary care and 18% from rheumatology. One-hundred and fifteen (40%) of those referred had been taking corticosteroids within the previous three months: this information was only provided in 49 referrals. In 32% of referrals, no serum cortisol measurement had been undertaken within the previous six months. In 20% of referrals, no indication was provided. Thirty-three (11%) SSTs were abnormal. Of these, 29 were in patients taking corticosteroids. No SSTs were abnormal among 64 patients with pre-test serum cortisol >300nmol/L or >400nmol/L according to the cortisol assay in use.

Conclusions: Referrals for SSTs often lack important information, such as the indication for testing and recent corticosteroid exposure. Up to one quarter of SSTs could be avoided if a serum cortisol was routinely measured prior to referral. Adopting a structured referral form that mandates provision of important clinical and biochemical data might reduce unnecessary testing.