Serum IgG4 level for malignancy prediction in indeterminate thyroid nodules among patients with or without autoimmune thyroid disease

Abstract

The incidence of thyroid nodules increased nowadays with the utter need to properly differentiate benign from malignant nodule to avoid unnecessary thyroidectomy along with the risk of complication related to surgery. Recently, IgG4 plays a critical role in several cancer related processes, Serum IgG4 has a potential advantage as diagnostic or prognostic marker for numerous cancers. Our aim was to detect the value of serum IgG4 level in prediction of malignancy in patients with indeterminate thyroid nodules. Our diagnostic accuracy study was conducted on 67 patients were randomly chosen from the endocrine clinic of Ain Shams University hospitals, in the period of 23 months who have suspicious thyroid nodules (indeterminate Fine-needle aspiration cytology (FNAC) and TIRADS 3 and 4 on ultrasound (US)). Total thyroidectomy was performed in all patients. They were then sub-grouped according to the post-operative histopathology into: Group (I): with confirmed benign nodules. Group (II): with confirmed malignant nodules. Ultrasonography imaging of thyroid nodules, fine needle aspiration biopsy and cytology of the thyroid nodule, thyroid profile, serum IgG4 by ELISA, serum anti TPO, anti TG by ELISA were done to all. Our Results revealed that patients with malignant nodules had a statistically significant higher levels of IgG4 than those with benign nodules (p=0.001). In addition, the cutoff point to differentiate between benign and malignant groups regarding plasma expression level of IgG4 level was > 180 mg/dl and AUC 0.875 (a sensitivity of 75% and a specificity of 100%, with a high negative predictive (NPV=94.8%)). A higher cancer prevalence was documented in patients with a positive autoimmune thyroid disease compared to those with a negative autoimmune thyroid disease (P = 0.001). In Conclusion we found that, the expression level of circulating IgG4 is a good predictor of malignant nodules in our studied group and positive autoimmune thyroid disease patients have a higher prevalence of suspicious cytology.