When plasma is refrigerated at 4ºC for up to 72 hours, proteins may precipitate (cryoprecipitate). If refrigerated serum and plasma both form a precipitate, then the precipitated proteins are referred to as cryoglobulins (CGs). If, however, precipitation develops after refrigeration of plasma but does not occur in cold serum, the plasma precipitate is referred to as cryofibrinogen (CF).
Cryoprecipitates — Both CGs and CF typically redissolve with warming to 37ºC, but the components of cryofibrinogen and cryoglobulin differ. CGs typically contain immunoglobulins and complement components. Although CF may also contain immunoglobulins, CF is characteristically composed of fibrinogen, fibrin, fibronectin and/or fibrin degradation products [1-3]. By definition, CF is undetectable in serum.
Some cryoprecipitates, particularly CGs may not completely redissolve when warmed. The residual material may be composed of fibrin.
Cryoglobulinemia — As defined above, a person whose serum and plasma form cryoprecipitates is referred to as having cryoglobulinemia. Three different types of CGs are recognized and the pathogenesis, clinical manifestations, and treatment associated with each type are discussed elsewhere. The following is a brief summary of the types of cryoglobulinemia: