Thirdly, additional tests may be required before becoming a donor for the first time. These tests may establish a platelet count. Newer automated platelet pheresis machines do that as the donation begins, and adjust accordingly the quantity of platelets to be drawn. Tests may also determine the donor's compatibility with particular recipients through an HLA (Human Leukocyte Antigen) test. Multiparous women may be excluded from becoming donors due to heightened TRALI risk. These tests usually involve nothing more involved than the drawing of several tubes of blood.