Glossary
CRYOGLOBULINS
Cryoglobulins are a group of proteins that form a precipitate or gelify at lower temperatures, and solubileze at 37 ° C. They are present in a wide range of clinical manifestations and are represented by a heterogeneous group of immunoglobulins (Ig), displaying single or mixed form patterns in the immunochemical analysis after purification. Following the Brouet classification, the following may be distinguished: - type I cryoglobulinemia in which the cryoprecipitate is formed by a single complete monoclonal Ig (IgG, IgA, IgM) or, more rarely, by a single light chain. This can be identified more frequently in patients with multiple myeloma, Waldenstom macroglobulinemia. The cryoprecipitate in type II cryoglobulinemia consists of one or more monoclonal Ig and polyclonal Ig and is associated with lymphoproliferative diseases, autoimmune diseases and HCV. Type III cryoglobulinemia involves a cryoprecipitate consisting in polyclonal or oligoclonal Ig and can be found in patients with autoimmune diseases and chronic infections. Positive cryoglobulinemia is strongly influenced by methodological rigour within the preanalytical and analytical phases. Excluding or confirming their presence relies on strictly controlling the temperature at which processes are carried out (sampling, transportation and centrifugation at 37°C, purification and characterization).
Blood is collected without the use of anticoagulants, sampled in test tubes at 37 ° C and maintained at this temperature until it coagulates. The serum is separated by centrifugation at 37 ° C at 1500g for 15 minutes. It is aliquoted into a test tube and into a Wintrobe tube, both kept at 4°C. The presence of cryoglobulins is signaled after a period of incubation at 4 ° C for 7 days, generally showing up as a white precipitate or gel. The reversibility of cryoprecipitate has to be verified by heating the serum precipitate aliquot. Cryoglobulins are measured as a percentage ratio between the serum’s precipitate and volume after centrifugation at 1500 g for 10 min at 4°C. Precipitates are resuspended in physiological saline solution or in a solution with PBS at 4°C and washed three times. Immunofixation is performed on the dissolved cryoprecipitate using total human antiserum and specific antisera for γ, α, μ, κ, λ. Cryoglobulins can thereby be classified into the taxonomy outlined above. In the presence of cryoglobulinemia, the laboratory report must include cryocrit data along with Ig classification, according to Brouet’s system.
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• Glossary