The polyethylenglycol (PEG) precipitation technique has been employed for the measurement of immune complexes in the circulation of 100 normal subjects and in 14 patients suffering from a variety of diseases (systemic lupus erythematodes, nephrosic syndrome, cryoglobulinaemia, Buckley's syndrome). Values higher than 0.80 UA on the absorption scale were considered pathological, namely 2 standard deviations above the mean (0.32 UA) in the subjects examined; in the patients, values between a minimum of 0.98 UA and a maximum of 2.38 UA were observed. Longitudinal study of these cases also pointed to the disappearance of immune complexes during therapy. The results suggest that the PEG precipitation technique can play an important part as a screening test in situations in which circulating IC pathology is suspected; it is also a sensitive means of monitoring treatment
