Overnight dexamethasone suppression test | Right Decisions

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SPEG (Scottish Paediatric Endocrine Group)
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Dynamic function tests for use in paediatric endocrinology
Overnight dexamethasone suppression test

Please update your RDS mobile app to version 4.7.1

We are pleased to advise that deep linking capability, enabling users to directly download individual mobile toolkits, has now been released on the RDS mobile app. When you install the update, you will see that each toolkit has a small QR code icon the header area beside the search icon – see screenshot below. Clicking on this icon will open up a window with a full-size QR code and the alternative of a short URL for sharing with users. Instructions are provided.

You may need to actively install the update to install RDS app version 4.7.1 to see this improvement. Installing this update is also strongly recommended to get the full benefits of the new contingency arrangements – specifically, that if the RDS website should fail, you will still be able to download new mobile app toolkits.

To check your current RDS version, click on the three dots bottom right of the RDS app screen. This takes you to a “More” page where you will see the version number. To install latest updates:

On iPhones – go to the Apple store, click on your profile icon top right, scroll down to see the apps waiting to be updated and update the RDS app.

On Android phones – these can vary, but try going to the Google Play store, click on your profile icon top right, click on “Manage apps and device”, select and update the RDS app.

Please get in touch with ann.wales3@nhs.scot with any questions.

Indications for the procedure

To identify Cushing’s Syndrome.

The Overnight Dexamethasone Suppression Test is used as an initial screening test.

Preparations for the test

No specific preparation required.

Ensure the patient is not taking steroids in any form.

Drug administration

Drug(s) Given

Dexamethasone 10 micrograms per kg body weight up to a maximum of 1 mg.
Available as scored 500 microgram tablets.
Round the dose to the dearest 250 micrograms (i.e. half a tablet).

How Given

Orally in tablet form.

Timing of Administration

Give the dose of dexamethasone between 23:00 and midnight.

Procedure

Time (minutes)	Action
23:00 to 00:00	Give dexamethasone orally.
09:00 next day	Take blood sample.

Samples required

Time
09:00	Cortisol

Interpretations

In normal subjects, the morning plasma cortisol concentration is suppressed to less than 50 nmol/l.

In patients with Cushing’s syndrome, such marked suppression is not observed.

Patients taking hepatic enzyme-inducing drugs (e.g. phenytoin, phenobarbitone) may have false negative results.