Coagulation and CTAD tubes are used for examination of coagulation parameters. Coagulation tubes contain a buffered sodium citrate solution. It is available with a citrate concentration of 0.109 mol/l (3.2%) or 0.129 mol/l (3.8%). The mixing ratio is: 1 part citrate solution to 9 parts blood. In addition to buffered sodium citrate, CTAD tubes contain theophylline, adenosine and dipyridamol.