From the Guidelines
Testing for cryoglobulinemia requires careful handling of blood samples to detect proteins that precipitate at cold temperatures, and the primary test involves collecting blood in a pre-warmed tube and then allowing serum to cool to observe for precipitation, as recommended by the most recent guidelines 1.
Key Considerations
- The sample should be refrigerated at 4°C for 72 hours and examined for the formation of a precipitate that dissolves when rewarmed to 37°C, confirming the presence of cryoglobulins.
- Additional testing includes cryocrit measurement, immunofixation or immunoelectrophoresis to classify the type of cryoglobulins, and complementary tests like rheumatoid factor, complement levels, and hepatitis C antibodies to identify underlying causes.
- Proper pre-analytical handling is crucial as improper temperature control can lead to false-negative results, as highlighted in a study on sample storage and handling 1.
Diagnostic Approach
- Patients should be warm before blood collection since cold temperatures can cause cryoglobulins to precipitate in the bloodstream, potentially affecting test accuracy.
- The presence of cryoglobulins may render falsely low serum IgM levels, and maintaining the serum sample in a warm bath can provide a more reliable serum IgM level measurement, as noted in a study on Waldenström macroglobulinemia/lymphoplasmacytic lymphoma 1.
- A comprehensive diagnostic approach should include a combination of clinical evaluation, laboratory tests, and imaging studies to identify underlying causes and assess disease severity, as recommended in guidelines for the management of mixed cryoglobulinemia syndrome 1.
Underlying Causes
- Hepatitis C virus (HCV) infection is a common underlying cause of mixed cryoglobulinemia syndrome, and treatment of HCV infection can lead to improvement or resolution of cryoglobulinemic vasculitis, as reported in a study on the treatment of chronic hepatitis C in patients with immune complex-mediated manifestations of HCV infection 1.
- Other underlying causes, such as lymphoproliferative disorders or autoimmune diseases, should also be considered and evaluated accordingly.
From the Research
Testing for Cryoglobulinemia
To test for cryoglobulinemia, the following steps are recommended:
- Blood samples should be collected, transported, clotted, and spun at 37°C to prevent premature precipitation of cryoglobulins 2, 3
- The serum should then be stored at 4°C in a Wintrobe tube for at least seven days to allow the precipitate to form 2
- The easiest way to quantify cryoglobulins is the cryocrit estimate, but this approach has low accuracy and sensitivity 2
- The precipitate should be resolubilized by warming to confirm that it is truly formed of cryoglobulins 2, 4
- The characterization of cryoglobulins requires the precipitate to be washed several times before performing immunofixation, a technique by which cryoglobulins can be classified depending on the characteristics of the detected immunoglobulins 2, 4
Importance of Proper Sample Handling
Proper sample handling is crucial for accurate and prompt diagnosis of cryoglobulinemia:
- The temperature should be maintained at 37°C until the serum is separated to avoid loss of cryoprecipitate during transport and storage 3, 5
- Improper sample handling can lead to false-negative results and delayed diagnosis 3, 5
- Laboratories should ensure that sample temperature is maintained at 37°C until the serum is separated to avoid missed diagnoses and improve the comparability of results 5
Classification and Clinical Features of Cryoglobulins
Cryoglobulins can be classified into three types:
- Type I: consists of only one isotype or subclass of monoclonal immunoglobulin 4, 6
- Type II and Type III: classified as mixed cryoglobulinaemia because they include immunoglobulin G (IgG) and IgM 4, 6
- Clinical features of cryoglobulinemia include purpura, weakness, arthralgia, and other symptoms such as skin ulcers, neurological and renal involvement 2, 4, 6