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

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

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.

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.

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.