Whole blood in 3.2% sodium citrate tube (blue top).
Fill one 3.2% citrated blue top tube (1.8 ml) to the blue fill indicator marked on the label. Do not short fill or over fill the citrate tube as this will cause erroneous results and the sample will be rejected. Immediately spin and separate the citrated plasma. Freeze the sample prior to shipping.
Under filling of the blue top tube may result in false prolongation of coagulation times.