The method of Platelet collection that allows the donor's remaining blood elements to return after separation is called:

The method of platelet collection that allows the donor's remaining blood elements to return after separation is known as apheresis. This process involves the use of a specialized machine that separates the blood components during the donation. During apheresis, the donor's blood is drawn, processed to extract specific components like platelets, and then the remaining components—such as red blood cells and plasma—are returned to the donor's circulation. This method is efficient and allows for the collection of a larger quantity of platelets in one session compared to traditional whole blood donation.

In contrast, autologous refers to blood that is collected from a patient for their own use, often before a surgical procedure. Homologous refers to blood collected from a donor for use in someone else. Fractionation involves separating blood into its components after collection but does not pertain to the return of the remaining elements to the donor as apheresis does.