A method for I 131 conversion ration utilizing the plasma inorganic I 131 fraction.

A method for calculating I(131) conversion ratios by utilizing the inorganic I(131) counts in the plasma at 24 hours is presented. Its chief advantage over previously used methods is that in cases of low conversion ratio it eliminates the large error introduced by fluctuations in the background of the counting equipment. The principle of the method depends upon the ability of silver to precipitate iodine (I(131)) in the presence of a slight excess of carrier iodine. Data are presented which show that low conversion ratios are frequently found in euthyroid patients, as has been the finding of other investigators.