Saliva is fine if quality is good, but it's incredibly hard to get people to follow protocol (no eating or drinking for 30 minutes, fill up to the line, shake t

Saliva is fine if quality is good, but it's incredibly hard to get people to follow protocol (no eating or drinking for 30 minutes, fill up to the line, shake the tube...) Blood you can't really mess up because a phlebotomist handles the protocol.