Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (877 page)

   If heparin is used as an anticoagulant in blood collection tubes, it may complex with fibrinogen, fibrin, and fibronectin and leads to falsely positive results. Therapeutically administered heparin may also produce falsepositive results. Therefore, collected blood should be anticoagulated with EDTA, citrate, or oxalate and maintained at 37°C until the plasma is collected.

   Fasting specimen recommended. Proper collection and transport of specimen is critical to the outcome of the assay.

   May cause erroneous WBC count when performed on electronic cell counter.

Suggested Reading

Nash JW, Ross P Jr, Neil Crowson A, et al. The histopathologic spectrum of cryofibrinogenemia in four anatomic sites. Skin, lung, muscle, and kidney.
Am J Clin Pathol.
2003;119: 114–122.

CRYOGLOBULINS

   Definition

   Cryoglobulins are abnormal serum proteins that precipitate at low temperatures and dissolve when temperature is raised. They cannot be identified by serum protein electrophoresis. Cryoglobulins are made up of monoclonal antibodies IgM or IgG, rarely IgA. IgM tends to precipitate at lower temperatures than does IgG cryoglobulin.

   Other names: cryocrit, cryoprotein.

   Cryoglobulins are classified as follows:

   
Type I
(monoclonal immunoglobulin, especially IgM κ type)

   Causes 25% of cases.

   Most commonly associated with multiple myeloma and Waldenström macroglobulinemia; other lymphoproliferative diseases with M components; occasionally it may be idiopathic.

   If present in large amounts (>5 mg/dL serum), blood may gel when drawn.

   Severe symptoms (e.g., Raynaud syndrome, gangrene without other causes).