Rumpled mentions many times that the blood draw must be into a chilled container and iced immediately. When my ACTH was drawn, I told the tech that. She said it was not necessary and they didn't do it. So I don't consider my ACTH levels as valid.
Here is what LabCorp says on their website:
"ACTH should be drawn between 7 AM and 10 AM.
Collect into iced plastic or siliconized glass lavender-top (EDTA) tube, noting time of collection. After venipuncture, immediately immerse the tubes in an ice bath. Separate plasma from cells by centrifugation within one hour after venipuncture.1,2 Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482) immediately. Freeze immediately and maintain frozen until tested. Contact LabCorp's supply department for special tubes. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested. "