Cryoglobulin

Overview

Cryoglobulins are abnormal immunoglobulins present in serum that precipitate at low temperatures (below 37°C) and dissolve again when reheated. These proteins may consist of immunoglobulins alone or a mixture of immunoglobulins and complement components. When these abnormal proteins precipitate inside blood vessels, they cause endothelial injury, leading to cryoglobulinemia, a condition that may affect multiple organ systems.

Cryoglobulins are classified into three types:

1. Type I: Monoclonal Ig (usually IgM, occasionally IgG or IgA). Often associated with plasma cell dyscrasias, such as multiple myeloma, monoclonal gammopathy of undetermined significance, Waldenström’s macroglobulinemia, and lymphoproliferative diseases like non-Hodgkin lymphoma and CLL.
2. Type II: Monoclonal IgM with rheumatoid factor (RF) activity plus polyclonal IgG. Common in chronic infectious diseases like hepatitis B, hepatitis C, and HIV, and also autoimmune diseases.
3. Type III: Polyclonal IgM with RF activity and polyclonal IgG. Seen in chronic infections (HBV, HCV, HIV), SLE, and rheumatoid arthritis.

Testing involves a cryoglobulin precipitation test, cryoglobulin subtyping, immunofixation electrophoresis, complement component assays, and related methods. Proper sample collection—using prewarmed tubes and maintaining samples at 37°C before serum separation—is crucial for accurate diagnosis.

Symptoms

The PDF describes a variety of symptoms associated with cryoglobulinemia due to vascular injury and immune-mediated inflammation.

General Symptoms:

1. Tiredness
2. Headache
3. Cough
4. Xerostomia (dry mouth)
5. Xerophthalmia (dry eyes)

Musculoskeletal Symptoms:

1. Arthralgia (joint pain)
2. Myalgia (muscle pain)

Renal Symptoms:

1. Glomerulonephritis
2. Isolated hematuria

Skin Symptoms:

1. Purpura
2. Petechiae
3. Erythematous pruritic purpura
4. Skin rashes and ulcers
5. Skin infarction
6. Raynaud’s phenomenon

These manifestations arise from precipitation of cryoglobulins within small- and medium-sized vessels, causing vasculitis and tissue injury.

Causes

The PDF lists several underlying conditions that produce cryoglobulins or lead to a positive cryoglobulin test.

Primary Causes:

1. Autoimmune diseases such as systemic lupus erythematosus (SLE) and Sjögren syndrome
2. Chronic infectious diseases: hepatitis B, hepatitis C, HIV, infectious mononucleosis, cytomegalovirus
3. Blood cancers and lymphoproliferative disorders including:
   1. Multiple myeloma
   2. Waldenström macroglobulinemia
   3. Non-Hodgkin lymphoma
   4. Chronic lymphocytic leukemia
4. Raynaud’s disease
5. Monoclonal gammopathies

Lab-Related Causes for False Results:

1. Improper handling leading to false negatives
2. Refrigeration before serum separation
3. Delayed processing
4. Using plasma or separator tubes (unacceptable specimens)

A positive test is defined by precipitation at 4°C that dissolves again at 37°C.

Risk Factors

Risk factors increase the likelihood of developing cryoglobulins or producing symptoms of cryoglobulinemia.

Medical Risk Factors:

1. History of autoimmune disease (SLE, rheumatoid arthritis, Sjögren syndrome)
2. Chronic viral infections: hepatitis C, hepatitis B, HIV
3. Existing lymphoproliferative disorders: multiple myeloma, Waldenström’s macroglobulinemia, lymphoma
4. Monoclonal gammopathies
5. Glomerulonephritis or nephrotic-range proteinuria
6. Vasculitis or unexplained skin lesions (purpura, necrosis, ulcers)

Testing-Related Risk Factors:

1. Drawing samples in cold environments
2. Using non-prewarmed tubes
3. Allowing blood to cool before clotting
4. Using insufficient sample volume (<3mL serum)
5. These factors increase the chance of inaccurate or false-negative results.

Prevention

Preventive measures in the PDF focus on proper specimen collection, handling, and processing to ensure reliable test results. Since cryoglobulins precipitate at low temperatures, maintaining correct temperatures is essential.

Sample Collection Prevention:

1. Draw 6 mL of blood into a prewarmed (37°C) plain red-capped tube.
2. Keep the blood at 37°C until clotting is complete.
3. Separate serum from cells within 1 hour of collection.
4. Transfer 3 mL serum to a standard transport tube.
5. Avoid plasma, SST tubes, and hemolyzed or lipemic samples.

Storage & Transport Prevention:

1. Maintain serum at room temperature or refrigerated after separation.
2. Do not freeze the sample (frozen samples are unacceptable).
3. Avoid refrigeration before serum separation to prevent false results.

Testing Preventive Measures:

1. Keep samples warm prior to separation to avoid premature precipitation.
2. Use temperature-controlled handling throughout collection and transport.
3. Use confirmatory methods such as immunofixation and complement assays for accurate subtyping.

Clinical Prevention:

1. Screen high-risk individuals (HCV, autoimmune diseases, lymphoproliferative disorders)
2. Identify unexplained vasculitis, purpura, or renal symptoms promptly
3. Use cryoglobulin subtyping to guide evaluation of underlying conditions