Testosterone and cortisol levels can be placed in the "red-tiger top" test tubes which have a serum sep-clot activator with a gel in the bottom of the test tube.  The corticosterone needs to be placed in a "plain red top" test tube which does not have the gel serum separator in it.

Hi Stéphane

Years ago we used heparin vacutainer (sodium heparin, green conventional closure) to dose progesterone in blood plasma, after centrifugation. Maybe you could have more useful information from the tube factory (Becton-Dickinson)...

For hormones testing our lab prefers tubes without clot activators, which can influence results.

Heparin bottles are recommended for test without clot.

Please, check what is recomended in ELISA test you are going to use

The Elisa test instruction sheet does usually state what sample to use; but if not, I too would recommend red tops without a serum separator.

None is the correct tube, you must use tubes to obtain the serum, they are sold in commercial kits.

 Thanks for your answers. I have checked with ELISA kits.

Jose, I don't get it.

In general, I used to use heparin tubes for hormone work and EDTA tubes for lipid work. However, I did radioimmunoassays rather than ELISA, so you will need to confirm either from the kit directions or from the manufacturer what is required. In my tests, the directions referred to serum samples (red cap tubes), but heparinized tubes were also possible to use.