Development of a competitive radioimmunoassay for human plasma fibronectin

A competitive radioimmunoassay (CRIA) for quantitating human plasma fibronectin levels has been developed and compared with a conventional immunoturbidimetry assay (IMTA). The assay ranges for CRIA and IMTA were 0.05-5 micrograms/ml and 100-1,000 micrograms/ml, respectively, and the lowest detectable amounts of fibronectin that differed significantly from zero were 17.6 ng and 50 micrograms. The correlation coefficient between CRIA and IMTA was r = 0.953 (p less than 0.001). We consider the CRIA as potentially useful in the identification and study of fibronectin in certain biological fluids where it may be present in low concentrations.