Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (386 page)

   The normal value is <80 μg/dL CG in serum (40% of normal individuals may have CG in their serum). The pathologic values found in cryoglobulinemia range from 500 to 5,000 mg/dL. To determine the nature of the CG, they must be redissolved by warming, and the sample analyzed for the various components of the immune complexes. This helps to classify the various cryoglobulinemia types.

   
Other pertinent laboratory findings

   Serologic evidence of hepatitis C, rarely B, and liver disease.

   Decreased serum early complement components.

   Serologic evidence of HIV infection.

   Renal disease (e.g., membranoproliferative glomerulonephritis) with proteinuria or hematuria.

   Skin biopsy may show cutaneous vasculitis.

   ESR and C-reactive protein are generally elevated.

   Limitations

   False-negative results may occur if the blood was cooled below 37°C during collection; if the blood clotted right away, centrifugation may remove the CG with the clot. The centrifugation too must be performed in a temperaturecontrolled centrifuge.

   The presence of CG may cause erroneous WBC counts on electronic counters.

Suggested Reading

Peng SL, Schur PH. Overview of cryoglobulins and cryoglobulinemia. In: Basow DS (ed).
UpToDate
, Waltham, MA: UpToDate, Inc.; 2013.

CRYOFIBRINOGENEMIA

   Definition

Cryofibrinogen (CF) is generated by a mixture of fibrinogen, fibrin, fibronectin, and other proteins that precipitate reversibly at cold temperatures in plasma, but not in serum. Cryofibrinogenemia may be classified as primary (essential, idiopathic) or secondary. The secondary form occurs in association with hepatitis C, other infections, malignancies, and inflammatory processes.