The interactions among impact factors affecting 131I treatment efficacy of Graves' disease

Objective: To evaluate the possible interactions among different impact factors possibly affecting the treatment efficacy of 131I in Graves' disease (GD). Methods: Six hundred and thirty two GD patients that had been treated by 131I, with or without antithyroid drugs (ATD), were included in this study. The impact factors were pre-defined as age (x1), sex (x2), mass of thyroid (x3), course of disease (x4), initial symptom (x5), condition of disease (x6), ATD treatment duration (x7), effective half life time (x8), maximum 131I uptake rate (x9), total dose of 131I (x10), dose of 131I per gram of thyroid (x11), TRAb (x12), TSI (x13), TgAb (x14), and thyroid microsomal antibody(TMAb) level (x15). Interactions among different impact factors were studied by t-test, χ2 test and multi-variant logistic regression. Results: Age, mass of thyroid, ATD treatment duration, maximum 131I uptake rate, dose of 131I per gram of thyroid tissue and TSI level were identified as independent impact factors affecting the 131I treatment efficacy on GD (χ2=6.908, t=-4.063, χ2=13.558, t=-2.553, t=4.528, χ2=9.716, all P<0.05) by uni-variant and multi-variate analyses. Loglinear and general linear model analyses showed that there existed multiple multiplicative and additive interactions among the factors of age, mass of thyroid, ATD treatment duration and maximum 131I uptake rate (likelihood χ2=8.176, P>0.05; F=2.928, 1.992, 2.629, 2.215, all P<0.05), which indicated that the treatment efficacy with co-existing multiple factors was not equal to simple summation of single factors. Conclusions: The interactions among multiple factors can cause indirect effect on 131I treatment, which might guide the prescription of 131I dosage for GD treatment. (authors)