Effect of filters A and B on HK from platelet concentrates. HK was measured in 20 platelet concentrates, subjected to filtration by filter A and filter B, and compared with the initial starting material (influent). The data are expressed as the percentage of initial HK. (A) The first 5 mL of filtrate collected. (B) The final pooled filtrate. Error bars are the ± SEM for the 5 mL and final samples.