Fig. 4

Results of subgroup analysis for patients who underwent thyroid fine-needle biopsy. * Results of subgroup analyses for the relationship between thyroid fine-needle aspiration biopsy and diagnosis of thyroid cancer only among patients who underwent thyroid fine-needle biopsy according to sex, income, financial independence rate of the local government, and median number of thyroid fine-needle aspiration biopsies. Relative risk (RR) was calculated by Poisson regression analysis with GEE adjusted for individual- and regional-level characteristics. Results were considered statistically significant if each bar marked to SD did not reach the cutoff line of 1.00