Fibronectin levels in normal subjects and patients admitted to a respiratory intensive care unit.

The mean serum fibronectin level of normal subjects, measured by radio-immunoassay, was 363 micrograms/ml (+/- 72 micrograms/ml; 1 SD). The levels were lower in younger subjects and in females using oral contraceptives. In most patients admitted to a respiratory intensive care unit fibronectin levels were low initially, and only remained low in those cases in which severe complications developed. There were no rapid fluctuations of fibronectin levels measured on a daily basis, suggesting therefore that a consumptive reduction of fibronectin is not a feature. The fibronectin molecule itself has abnormal properties in pathological cases and is poorly precipitable by heparin. These studies do not support the proposal that administration of plasma or cryoprecipitates would be beneficial chiefly because of the fibronectin content.