Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (879 page)

   To detect cryoglobulinemia in patients with symptoms indicating or mimicking Raynaud disease, cyanosis, and skin ulceration

   To monitor course of connective tissue disorders

   Interpretation

   Cryoglobulins with a detected monoclonal protein normally prompt a clinical investigation to determine if an underlying disease exists.

   Limitations

   Cryoglobulins are not to be confused with cryofibrinogen (see above section), which precipitates only in plasma, under cold conditions.

   Failure to maintain sample at normal body temperature before centrifugation can affect results.

   A recent fatty meal can increase turbidity of the blood.

Suggested Readings

Coblyn JS, McCluskey RT. Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 3-2003: a 36-year-old man with renal failure, hypertension and neurologic abnormalities.
N Engl J Med.
2003;348:333–342.

Kallemuchikkal U, Gorevic PD. Evaluation of cryoglobulins.
Arch Pathol Lab Med.
1999;123: 119–125.

CRYSTAL IDENTIFICATION, SYNOVIAL FLUID

   Definition

   Synovial fluid, often referred to as “joint fluid,” is a viscous liquid found in the joint cavities. Synovial membranes line the joints, bursae, and tendon sheaths. The function of the synovial fluid is to lubricate the joint space and transport nutrients to the articular cartilage.

   The aspiration and analysis of synovial fluid may be done to determine the cause of joint disease, especially when accompanied by an abnormal accumulation of fluid in the joint (effusion). The joint disease may be crystal-induced, degenerative, inflammatory, or infectious. Morphologic analysis for cells and crystals, together with Gram stain and culture, help in the differentiation.

   Normal synovial fluid is a clear, pale yellow, viscous liquid that does not clot. When a synovial membrane is inflamed for any reason, the WBC count in the synovial fluid increases.