Storage of platelets for tests of platelet function: Comparison of two methods of pH control

A comparison was made of two methods to control the pH of platelet-rich plasma (PRP) stored for tests of platelet function. Citrated PRP at 37°C was maintained at pH 7.3–7.4 by incubation either in a controlled CO 2/air environment or in a plastic syringe from which all air was expelled. At intervals over 2–5 hours platelet aggregation induced by ADP and collagen was measured. Plasma β-thromboglobulin (βTG) was assayed to assess liberation of βTG from platelets during storage. Platelet aggregation responses were more stable when PRP was stored in a syringe. Liberation of βTG from platelets did not occur in this system, but did occur in the CO 2 system in many experiments. The differences between the two systems were not due to the lower pO 2 levels in the syringe, but were probably related to the presence of an air/liquid interface in the CO 2 system. The syringe system of storage is a simple method of pH control which offers better preservation of platelet function than a controlled CO 2/air environment.