Internal quality control and external quality assurance of platelet function tests.

Internal quality control (IQC) and external quality assurance (EQA) are distinct processes that contribute to ensure the overall quality (i.e., correctness) of laboratory test procedures. This review summarizes the current position of IQC and EQA in platelet function testing. These processes are in their infancy for these tests, despite the many years in which these tests have been performed within diagnostic hemostasis laboratories. This is understandable, due to the many challenges imposed by the requirements of the tests themselves and of the IQC and EQA processes, namely the regular availability, and ongoing supply and transport, of fresh blood containing functional platelets for testing within a very short time frame. Nevertheless, recently published studies have shown that IQC and EQA are both feasible for platelet function testing, although these processes have typically been undertaken in some modified form compared with other tests of hemostasis. Several EQA organizations are currently involved in providing support to laboratories that perform platelet function testing. Initiatives to date include cross-laboratory challenges for PFA-100 testing, several patterns of practice surveys, and several other EQA challenges related to dense granules and light transmission aggregometry. EQA organizations may be best placed to act as facilitators to the process of improving diagnostic testing for platelet function, which supplements the role of expert organizations.