A test that measures the presence of cryoglobulins in the blood. Cryoglobulins are abnormal proteins . They become insoluble to varying degrees at temperatures below 37 degrees C (98.6 degrees F). Cryoglobulins form complexes that precipitate if blood is cooled and then rewarmed. Exposure of the face or hands, for example, of people with cryoglobulins can cause formation of precipitates that can block small blood vessels.