Is only Thyroid Peroxidase Antibody Sufficient for Diagnosing Chronic Lymphocytic Thyroiditis?

OBJECTIVES: Recently, only anti-thyroid peroxidase (anti-TPO) has been suggested as an autoantibody in the diagnosis of chronic lymphocytic thyroiditis (CLT). In contrast, anti-thyroglobulin (anti-Tg) positivity has also been reported to be important. To evaluate this relationship more clearly, we planned to retrospectively investigate the autoantibody levels of the patients who underwent thyroid surgery for various reasons and those with CLT in postoperative pathology. METHODS: We evaluated 670 patients who underwent thyroid surgery (total/subtotal thyroidectomy) for various reasons at our hospital between January 2015 and March 2017. Patients with indications of Graves' disease, toxic multinodular goiter, and all malignancies except for thyroid papillary carcinoma (TPC) were excluded. Eighty-nine patients whose pathology findings were compatible with CLT and preoperative thyroid autoantibodies were identified enrolled in to the study. Patients with absence and presence of thyroid antibodies were included in the seronegative CLT group and seropositive CLT group, respectively. In addition, patients were divided into thyroid papillary carcinoma (TPC) and benign groups. RESULTS: According to the study criteria, 89 (83 females, six males) (mean age, 46.08±11.19 years) patients who had preoperatively identified autoantibodies were detected. Anti-TPO positivity was found in 47 (52.8%) cases, whereas anti-Tg positivity was found in 49 (55.1%). Only anti-TPO positivity was found in 18 (20.2%) cases, whereas only anti-Tg positivity was detected in 20 (22.5%). Twenty-two (24.7%) of the patients were seronegative. On comparing the seronegative and seropositive groups, seronegativity was more frequent in male patients (p=0.03). Thyroid-stimulating hormone was found to be significantly higher in the seropositive group (p=0.01). TPC was detected in 36 (40.4%) of all cases. No difference regarding age, thyroid function tests, and antibody levels was found between the benign and TPC groups. CONCLUSION: Although all of our cases were histopathologically diagnosed with CLT, serologically, 75.3% of thyroid autoimmunities could be shown when both antibodies were evaluated together. When only anti-TPO was considered, this rate decreased to 52.8%. Therefore, anti-Tg appears to be still important in showing autoimmunity. Prospective studies are needed to evaluate this relationship more clearly.