Objective  To investigate the value of combined serum thymidine kinase 1 (S-TK1) and thyroglobulin (Tg) detection in the differential diagnosis of benign and malignant thyroid nodules.

  Methods  S-TK1 and Tg levels were retrospectively detected with an enhanced chemiluminescence dot blot assay and chemiluminescence immunoassay in 81 cases of malignant thyroid nodules, 62 cases of benign thyroid nodules, and 40 cases of normal controls in the Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, between October 2015 and September 2017. To compare the S-TK1 and Tg levels in each group, and to evaluate the clinical value of detecting S-TK1 and Tg, in the differential diagnosis of benign and malignant thyroid nodules, Logistic regression and Receiver Operating Characteristic Curve (ROC) were performed.

  Results  The S-TK1 and Tg levels in patients with malignant thyroid nodules (5.33±3.38) pmol/L, (61.86±24.80) ng/mL were significantly higher than in those with benign nodules (1.40±0.99) pmol/L, (45.13± 15.80) ng/mL and in normal controls (1.35±0.41) pmol/L, (40.88±15.45) ng/mL (P < 0.05). The ROC of S-TK1, Tg, and P of the regression equation showed that the S-TK1 and Tg cut-off values were 2.320 pmol/L and 63.40 ng/mL, respectively. The area under the curve (AUC), sensitivity, and total effective rate of S-TK1 were significantly higher than those of Tg (P < 0.05). The cut-off value of P was 0.372, and the AUC, sensitivity, and total effective rate were significantly higher than those of S-TK1 and Tg (P < 0.05).

  Conclusions  S-TK1 was indicative than Tg in the differential diagnosis of benign and malignant thyroid nodules. The combined detection of S-TK1 and Tg can significantly improve the sensitivity and total effective rate of diagnosis, and as such, the combined detection of both parameters can assist the differentiation of benign and malignant thyroid nodules.