Dear Colleagues

 

I recently submitted a question to the Mailbase about the use of the low dose synacthen test, which uses a dose of 500 ng/1.73m². Our tertiary referral centre has requested that we use the LDST in children.  I wondered how often and under what circumstances was this test used in favour of the standard SST, and also needed advice on sampling times and cut-offs/interpretation.  Some of you asked if I’d share my findings, so they are summarised below.

 

Centre 1: Sample at 0, 15, 25 & 35 mins. No interpretation provided.

 

Centre 2: Commence between 9-10 am. Sample at 0, 10, 20, 30, 40 & 60 mins. Same cutoff as standard SST at 30 mins. Hardly ever use except when questioning iatrogenic adrenal insufficiency.

 

Centre 3: Commence at 14.00h when endogenous ACTH is low. Sample at 0, 10, 15, 20, 25, 30, 35, 40. Normal response is a peak of >550 nmol/L and an increment of >200. Can see blunted response if on inhaled steroids.

 

Centre 4: Do not bother with LDST – too many pitfalls of low dosage, timings, lack of interpretation etc

 

A group from Sheffield Children’s Hospital conducted an audit in 2009 (Sachdev et al, Endocrine Abstracts 23 P18), which addressed all the questions raised in my initial enquiry. Not surprisingly they found considerable variation in practice and suggest the need for standardisation.

 

Hope you all have a good weekend

 

Kind regards

 

Avril

 

Avril Wayte

Consultant Biochemist

Clinical Chemistry

Ysbyty Gwynedd

Bangor

Gwynedd

Clinical Lead for Biochemistry, BCUHB