We are using cortisol as our primary biomarker or outcome of interest in our research. What are the precautions needed with measuring cortisol? From an economic perspective, how much will it cost if for example if we have to measure basal cortisol levels three times before and then three times after an intervention? many thanks for replies :)
Hi Kesava,
Assuming you are referring to collecting salivary cortisol, I would suggest you read the saliva collection and handling advice from Salimetrics:
http://www.salimetrics.com/assets/documents/Saliva_Collection_Handbook.pdf?/documents/Saliva_Collection_Handbook.pdf
The cost of collection and assay of the samples will depend on the method you choose and the number of participants. I would recommend passive drool method and EIA for measurement...for this you will need to purchase polypropylene cryogenic vials, saliva collection aids (or plastic straws if your on a tight budget!), and the assay kit. I purchase everything through Stratech scientific...call them to quote you. You can save money by buying 5 plate EIA kits. Read the cortisol assay manual and check you have access to research tools you require (pipettes, plate reader, etc).
If they are collecting at home you will need to think about logistics as well, they can freeze their samples at home and you can provide express post bags for them... or if you want to save money, pick them up yourself. I would consider collecting 3 samples on each day to capture diurnal rhythm or make sure morning samples are collected at the same time of day.
Hope that helps.
Mazen
Hi Mazen,
Thank you so much for the reply. Yes, it is salivary cortisol (should have mentioned it clearly in the question). So you would recommend passive drool, is there any particular advantage for using that? as i think salivary flow rate doesnt impact cortisol?
I shall read the manual, thank you for sharing the link.
Regarding logistics, thats a very important point you made, thank you, didnt even think about the express bags, so definitely helps :).
regarding collecting samples, wont CAR (cortisol awakening response) be enough instead of 3 samples/day?
yes, your answer was very helpful, thank you for the same :)
Kesava
No worries. Passive drool is advantageous as you're collecting whole saliva and not introducing foreign substances. Cotton absorptive materials are known to alter results and you may collect from specific glands (e.g. if placed under tongue). Granger et al. has many articles which will help you design your protocol. Waking cortisol samples should be ok if you wish to observe change over days.
Good luck!
Mazen
Hi Kesava,
About sampling of saliva for cortisol measurement, you should also be careful to the volume of saliva collected so as to express your results in ng or pg of cortisol per ml of saliva produced... Indeed, stress can increase salivation in certain species and so cortisol would be diluted and appear with a fewer concentration through the measurement depsite an increase of stress... Cortisol is the best known indicator of stress but it has to be interpreted carefully because it is more an indicator on emotion in general whatever the valence of the emotion is (negative or positive)... For example, you should have read in the documents furnished by Mazen that you cannot give food to animals before the sampling because it will also increase cortisol secretion, as arousing or physical exercice do... All these actions may interfere with you results regarding the stress event on its own.
Also when you choose the cortisool assay kit, be carefulo the wroking range of the assay (i.e. the standard range) since cortisol is pretty diluted in saliva : the best is to find a kit already validated for use in saliva and with a sensitivity fit for your purpose.
Good luck!
Hi Cecile,
Thank you so much for the reply. Thanks for highlighting an important aspect (Volume of cortisol). I will choose the kit carefully as suggested :)
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