The laboratory evaluation of platelet dysfunction

An algorithm for platelet function testing is presented in Fig. 2. The proposed algorithm takes into account the importance of a thorough clinical bleeding history and provides an integration of screening tests with more specific diagnostic assays. As our understanding of the biochemical and molecular aspects of platelet function becomes increasingly refined, it is becoming clear that current clinical testing strategies may not be adequate to identify all significant platelet function defects. The repertoire of distinct platelet agonists is increasing to allow a more discrete look at the function of isolated platelet membrane agonist receptors, especially those involved in platelet activation by ADP, thrombin, and collagen. In addition, FACS analysis of platelets, with emphasis on surface membrane glycoprotein expression, may offer a more specific and quantitative view of platelet membrane constituents and their function. Furthermore, screening tests evaluating platelet function under physiologic and pathologic flow conditions are becoming important adjuncts to in vitro analyses, and may accentuate platelet function abnormalities, not easily discerned by platelet aggregation studies. It remains to be seen whether such screening tests will better predict clinical bleeding or thrombotic risk.