In this study, we identified clinical and laboratory markers of malignant thyroid nodules and determined whether systematic inclusion of these data could improve diagnostic accuracy of fine-needle aspiration biopsy in solitary thyroid nodules. The patients were 24 men and 105 women who underwent surgical removal of solitary thyroid nodules and had adequate fine-needle aspiration biopsy performed prior to surgery. Including fine-needle aspiration biopsy's diagnosis of suspected of malignancy in the same category as malignancy, the sensitivity and specificity of fine-needle aspiration biopsy were 71.4% and 85.1%, respectively, with an accuracy of 82.2%. Using stepwise linear regression analysis, clinical data, i.e. increasing age, irregular nodule surface, hard consistency of nodule, and high serum thyroglobulin concentration, were associated with an increased risk of malignancy when the cytological result was excluded. When cytology was also considered, male sex, irregular nodule surface and high serum thyroglobulin concentration were found to be associated with an increased risk of malignancy. The diagnostic value of clinical data alone, even in combination with cytology or laboratory data, was inferior to that of fine-needle aspiration biopsy alone. The specificity and accuracy of fine-needle aspiration biopsy could be increased to 98.0% and 90.7%, respectively, whereas its sensitivity was decreased to 64.3% when these variables were considered in combination. Therefore, of fine-needle aspiration biopsy, clinical and laboratory data, fine-needle aspiration biopsy alone has the highest diagnostic value, which can be increased only when both clinical characteristics and serum thyroglobulin concentration are systematically included.
Serum thyroglobulin concentration as an index of iodine status in adults