Does anybody have experience in measuring cortisol in the saliva of domestic cats?
We tried some measurements (using a commercial ELISA kit to measure in human saliva), but got extremely bad double values (13-58%), making me wonder whether there is something in cat saliva that interferes.
There is no literature on measurements of cort in cat saliva (except on small study on jaguars), but I guess others might have tried before, but also experienced significant difficulties, which never got published?
Usually Elisa methods are not sufficient for measurement of cortisol in saliva. We have received excellent values with very good precision using RIA Tests.
Bei Hunden, erwachsenen Menschen und Säuglingen. Mit einem Wattebausch wurde Saliva gesammelt, dann scharf zentrifugiert und anschließend eingefroren zum gesammelten Messen. Wir verwendeten dabei einen RIA von IBL.
I have used Elisa and RIA both to measure cortisol in Sheep and Cattle. My data which come out of over 30 observations says that ELISA is more precise than RIA..I don't know about cats...
Rias are usually carried out with douplicates in order to improve precision. However in the case of cortisol in saliva you have the problem of detection limits with Elisas or automatic analysers. Since the cortisol concentration in saliva is much (ca. 10 times) lower if compared to serum, you will always have the problem of detection limit with antiibody-tests. In case of RIAs, this limit of detection is much lower.
Sighart Golf
We used an ELISA from IBL especially for cort in saliva. So while RIAS are often more sensitive, this cannot explain why our double values are so terrible.
We now measured the PH of the cat saliva and found it to very high, probably way too high with PH=9.5. So what would be the best way to bring the PH down to 7?
As far as I know, the pH in saliva is lower (pH 5-8) than in serum or plasma (see Geigy tables). When saliva is standing at room temperature for longer periods, the pH increases, possibbly due to loss of CO2. Therefore, saliva samples should be saved in closed containers, such as Eppendorf tubes. A pH of 9 or more seems to me unplausible. I never found pH values above pH 8,3. Children tend to have values above pH 8.
When a test provider characterises the properties of an analytic test, the provider has to define the lower test limit. To find this test limit, zero-concentration solution is tested several times and the 3fold standard deviation is calculated. This value is then defined as the lower limit of detection of the test.
This makes it clear, that all samples with analyte concentration close to this limit show a gigantic variation of results.
When discussing sensitivity of RIA and ELISA-tests, you have to consider, that with a RIA, especially a C14-Test, you measure each molecule containing the Isotope in contrast to the ELISA, where you have a detection limit of maybe around 10-12E.
Sighart Golf
Hi, is there a validated RIA kit for feline salivary cortisol?
Thanks
Yes!
There are many references which already have done so. Please google it. or take a look up here: (https://scholar.google.co.kr/scholar?q=salivary+cortisol+in+cat&hl=en&as_sdt=0&as_vis=1&oi=scholart&sa=X&ved=0ahUKEwi4ndyj6c3KAhUDY6YKHaKdDNEQgQMIGDAA)
Thanks Jalil. I have found several references for human, sheep, calf, horse, dog, but not for cats.
We did not manage to reliably measure cort in cat saliva. Cat saliva has a very high Ph, which could be part of the problem.