Protein composition of clots detected in pooled cryoprecipitate units

BACKGROUND: On rare occasions, upon thawing of stored cryoprecipitate components, clots are observed on visual inspection. Although it has been assumed that the clot reflects fibrinogen to fibrin conversion, there are few published studies that document that this assumption is correct. Our studies were conducted to further identify the protein characteristics of the clotted material. STUDY DESIGN AND METHODS: Clotted material isolated from four thawed cryoprecipitate pools was examined by solubilization procedures and electrophoresis analysis. RESULTS: Solubilization of much of the clotted material in phosphate‐buffered saline warmed to 37°C suggested the presence of soluble fibrin. Gel electrophoresis under reducing conditions showed that the most prevalent bands exhibited molecular weights corresponding to the α, β, and γ subunits of fibrinogen with a much lighter band exhibiting the molecular weight of fibrinogen γ‐γ dimer, consistent with the presence of partially crosslinked fibrin. The presence of the dimer indicated that the clotted material was caused by the action of thrombin, but also reflected the action of Factor XIIIa. No ongoing clot formation was observed. CONCLUSION: Our studies indicate that, on rare occasions, fibrinogen conversion to fibrin is responsible for observable clots in thawed cryoprecipitate pools. These clots are structurally heterogeneous, including both noncrosslinked (soluble) and crosslinked (insoluble) fibrin. This diversity in the fibrin structure may account for some of the diversity in the limited literature regarding their presence in cryoprecipitate pools.