Blood collected on plain tube (without anticoagulant) must.. Be incubate at 37c for 30 min NIL NAM July 02, 2017 Blood collected on plain tube (without anticoagulant) must: a. Be incubate at 37c for 30 min*** b. Not be clotted c. Be hemolysed d. Be mixed. Share This: Facebook Twitter Google+ Stumble Digg