Читать книгу Transfusion Medicine - Jeffrey McCullough - Страница 101

In one study of 2,069 plateletphereses in 352 donors, or an average of six procedures per donor, the following important observations were made that formed the basis of subsequent FDA regulations for the selection and monitoring of cytapheresis donors: (a) among women, platelet counts averaged 12% higher than those of males; (b) about 3% of all donors had platelet counts less than 150,000/mL before their first platelet donation; (c) the preapheresis platelet count was the best predictor of the postapheresis platelet count; (d) if donors with a preapheresis count of less than 150,000 were excluded, only 13% of donations resulted in a postapheresis count of less than 100,000; (e) the platelet count decreased about 30% immediately after apheresis; (f) the platelet count returned to normal about 4–6 days after apheresis; and (g) there was a slight rebound in platelet count above the initial count about 8–11 days after apheresis. Although the decrease in platelet count varies with the procedure used, a decrease of 20–35% generally occurs and the platelet count returns to baseline levels about 4 days after donation [77]. The platelet count decreases less than expected based on the number of platelets collected [78] because platelets are mobilized during the apheresis procedure [79].

A platelet count is not necessary before the initial donation because the decrease in platelet count following donation is not so extensive as to create a risk for the donor. At least 48 hours must elapse between platelet donations. If donors are to donate more frequently than every 4 weeks, a platelet count must be done to ensure that it is at least 150,000/μL before a subsequent donation. The platelet count can be obtained before the donation, or a count obtained after a previous donation can be used. Platelet donors should not have taken aspirin or drugs that interfere with platelet function, or must wait the specified time interval for that drug before donating (e.g., 3‐day waiting period for aspirin).