INTRODUCTION

There are numerous available laboratory methods for the assessment of platelets. These range from the quantification of platelet count and size to measurement of the bleeding time, platelet aggregation, and so forth (Table 8.1). Techniques applied include flow cytometry, point-of-care assessment devices (e.g., PFA-100®), and enzyme linked immunosorbent assay (ELISA) (e.g., laboratory markers of in vivo platelet activation). Other novel techniques for the study of platelets/megakaryocytes (MKs) are available, and include manipulation of gene expression in MKs, use of antisense oligonucleotides, green fluorescene protein (GFP) fusion proteins, mRNA and cDNA libraries from platelets or MKs, gene array technologies, etc. This chapter provides an overview of these techniques.

BLOOD SAMPLING

Accurate assessment of both platelet count and function can be highly dependent on the care and attention paid during both venipuncture and blood processing.

The donor should not be stressed and in the preceding week should not have had medications that may affect platelet function. A 19- to 20-gauge needle and plastic syringe should be used for venipuncture and the time from venipuncture to laboratory testing should be standardized, because loss of CO2 from the sample results in a rise in pH that generally increases platelet responsiveness to agonists. Hemolysis must be avoided, as lysed red blood cells liberate the platelet-aggregating agent ADP.