[The use of laser nephelometry for the determination and computer-assisted calculation of the fibronectin concentration in various body fluids (author's transl)].

We report a laser-nephelometric procedure for the determination of the concentration of fibronectin in various human and animal body fluids. The method is precise (CV intra-assay 2.1%), sensitive (the detection limit is 1.2 mg/l fibronectin), rapid, relatively simple and can be totally mechanized. By use of programmable calculators an electronic evaluation of the scattered light signals is possible. The antigen concentrations determined both by laser nephelometry and radial immunodiffusion show a coefficient of correlation of r = 0.859. In plasma of healthy men the mean concentration of fibronectin is 291 mg/l; women have a significant lower concentration of 259 mg/l. Increased levels of plasma fibronectin were found in patients with carcinomas of the female genital tract and Morbus Crohn. Synovial fluids obtained from inflammatory joint diseases contain significantly higher concentrations of fibronectin (318 mg/l) than those from non-inflammatory joints. The range of concentration of fibronectin in seminal plasma is similar to that in blood plasma, but a large inter-individual variation was observed. Extremely low antigen concentrations (0.41 mg/l) were determined in normal liquor cerebrospinalis, but under pathological conditions a significant increase occurs, which correlates strongly with the cell count. Low levels of fibronectin (16 mg/l) were also found in amniotic fluid at the end of pregnancy.