Effect of filters A and B on specific LK from platelet concentrates. Specific LK was measured in 20 platelet concentrates, subjected to filtration by filter A and filter B, and compared with the initial starting material (influent). Total plasma protein was also measured in each sample. The data are expressed as the percentage of initial specific LK. (A) The first 5 mL of filtrate collected. (B) The final pooled filtrate. Error bars are the ± SEM.