To test the use of a Microdialysate Automated Collection Device for cortisol sampling and to assure reproducibility in the LUMC of data reported by others

Accurate determination of cortisol and its circadian rhythm is essential not
only in the diagnostic evaluation of the HPA axis, but also in the evaluation
of patients with adrenal insufficiency. Measuring circulating free cortisol has
been recognized to be the most optimal diagnostic tool. However, the currently
available biochemical screening tests all have their limitations. In addition,
stress-free sampling is cumbersome, because for example a venepuncture causes a
reactive stress response thereby affecting ACTH and (for later measurements)
cortisol levels. To accurately measure the changes in hormone concentrations
frequent measurements over extended periods are necessary. For this purpose, a
computerized, automated sampling system, which allows repeated stress-free
sample collection for the measurement of hormones in tissue using a small
subcutaneous microdialysis probe was developed. In Leiden, we have been able to
successfully test this sampling system in 2015 in 3 healthy subjects without
any complications or problems during the procedure. However, the cortisol
values measured in the dialysate in Leiden (at mid-day) were lower than the
values measured by our colleagues in Bristol, despite the use of the same
materials and analysis in the same laboratory. These differences in measured
values are not well understood. We believe it is important to prove the ability
to measure subcutaneous cortisol profiles with this device before the start of
a larger research protocol using this measurement technique, which is true for
the comparability to other centres and for intra individual (pulsatile)
profiles. There is a particular interest to know whether we can detect a
circadian profile and whether physiological morning levels are indeed higher
than the previously measured mid-day values. When physiological profiles turn
out to be not measurable, it would be interesting to see whether
supraphysiological cortisol levels (e.g. after hydrocortisone intake in adrenal
insufficient patients) are to be detectable.

- To assure reproducibility of results reported by other groups to see whether
the current SOP should be adjusted for local use in order to let the device be
of value to future research projects of our department.
- To confirm the ability to measure a pulsatile profile in participants (and
patients with adrenal insufficiency with temporary supraphysiological levels
intake of their usual medication if necessary).
- To finalize a new research proposal and protocol using the results of this
pilot study.

Step 1:
We will connect the device to a maximum of ten healthy subjects and take
microdialysis samples within 24 hours before disconnecting the device again.
This will enable us to measure the physiological morning cortisol peak.

Step 2 (only performed when step 1 produces insufficient data):
We will connect the device to a maximum of ten patients with adrenal
insufficiency on hydrocortisone replacement therapy and take microdialysis
samples within 24 hours before disconnecting the device again. Because these
subjects are on hydrocortisone therapy, supraphysiological cortisol levels
after medication intake should be visible in their tissue cortisol profiles in
case of reliable measurements with the Microdialysate Automated Collection
Device. We will not discontinue or change prescribed medication.

The device is currently used for research purposes by different international
groups. We work closely together with colleagues from Bristol, whom have
developed this system and have a lot of experience using it. Complications
during or after use of this device have never been reported. No problems have
occurred during our former measurements using this technique.

Placement of a subcutaneous catheter and the sequential draws of extracellular
fluid is a safe procedure, with a low chance of malfunctioning of the catheter
requiring placement of a new one. During positioning of the catheter, the skin
will be locally anesthetized, so no pain will be experienced by the subject.
Also after placement during sampling and while removing the catheter, the
subject will not experience any pain. Theoretically, an infection of the
insertion side could occur, despite sterile placement . This has not been
reported in earlier studies with the device, nor has been the case in any of
our former participants. In case this does happen, the probe will be removed
and (local or oral) antibiotics will be prescribed if necessary. There is a
minimal risk of development of subcutaneous oedema or hematoma on the insertion
site.

The anesthetization can be somewhat sore/painful, however this is limited.
Showering with the catheter in situ is not possible and sleeping while the pump
makes a buzzing sound can be experienced as uncomfortable.