Measuring serum thyroglobulin in patients with follicular thyroid nodule: its diagnostic implications

To determine the diagnostic implications of measuring the serum thyroglobulin level in patients with a solitary follicular thyroid tumor, a retrospective study was conducted on 122 consecutive patients with a solitary follicular thyroid nodule who underwent thyroidectomy. Data for eight variables were collected: the serum thyroglobulin (Tg) level (microgram/l), age, maximum diameter of the nodule, gender, histopathologic type, presence or absence of metastases, macroscopic characteristics of the cut surface of the resected tumor, and smoking habit. Multiple regression analyses were used to investigate the relationships between the serum Tg level and the seven other variables. The diagnostic value of serum Tg was examined by means of receiver operating characteristic (ROC) curves. There were significant correlations between the serum Tg level and the maximum diameter of the nodule, the macroscopic characteristics, and the smoking habit. The sensitivity and specificity of the serum Tg level with a cut-off value of 1,000 micrograms/l were 57% and 86%, respectively. The likelihood ratio favouring follicular carcinoma associated with the serum Tg > 1,000 micrograms/l was 4.41. Measuring the level of serum Tg may be useful in discriminating follicular carcinoma from follicular adenoma, but since there may be some biases in this retrospective study, the results are less definitive. Further research activities are mandatory to obtain valid evidence.