Filtration of platelet-poor plasma specimens yields platelet-free plasma. Application for batch analysis of beta-thromboglobulin and platelet factor 4

The authors investigated filtration of platelet-poor plasma through a 0.2-μm filter for the analysis of beta-thromboglobulin (β-TG) and platelet factor 4 (PF4) in frozen specimens. Platelets were detected by electron micrograph in the platelet-poor plasma preparation without filtration. No platelets or platelet fragments were seen after filtration. Freezing the unfiltered specimens resulted in a significant increase in the β-TG and PF4 concentrations, presumably because of release of these proteins from the platelet alpha-granules during freezing and thawing. There was no change in the PF4 levels and only a slight decrease in β-TG levels after freezing of the filtered specimens. The filtered samples could be frozen for later batch analysis, resulting in considerable cost savings to the laboratory.