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Background: The worldwide incidence of papillary thyroid carcinoma (PTC) has increased. Efforts to reduce overtreatment follow two approaches: limiting diagnostic workup of low-risk thyroid nodules and pursuing active surveillance (AS) after diagnosis of microscopic PTC (mPTC). However, most studies on AS have been performed in countries with a relatively high proportion of overdiagnosis and thus incidental mPTC. The role of AS in a population with a restrictive diagnostic workup protocol for imaging and fine-needle aspiration remains unknown. Therefore, the aim of this study was to describe the proportion and characteristics of patients with mPTC in the Netherlands and to describe the potential candidates for AS in a situation with restrictive diagnostic protocols since 2007. Methods: All operated patients with an mPTC in the Netherlands between 2005 and 2015 were identified from the Netherlands Cancer Registry database. Three groups were defined: (Group 1) mPTC with preoperative distant or lymph node metastases, (Group 2) mPTC in pathology report after thyroid surgery for another indication, and (Group 3) patients with a preoperative high suspicious thyroid nodule or proven mPTC (Bethesda 5 or 6). Only patients in Group 3 were considered potential candidates for AS. Results: A total of 1018 mPTC patients were identified. Group 1 consisted of 152 patients with preoperatively discovered metastases. Group 2 consisted of 667 patients, of whom 16 (2.4%) had lymph node metastases. There were 199 patients in Group 3, of whom 27 (13.6%) had lymph node metastases. After initial treatment in Group 3, 3.5% (7/199) of the patients had recurrence. Conclusions: Restrictive diagnostic workup strategies of patients with small thyroid nodules lead to limited patients eligible for AS and a higher incidence of lymph node metastases. We believe that there is limited additive value for AS in countries with restrictive diagnostic workup guidelines such as in the Netherlands. However, if an mPTC is encountered, AS can be offered on an individual basis.

Objective Hypoparathyroidism is a common complication after thyroidectomy. It is not yet possible to predict in which patients hypoparathyroidism will persist. We aim to determine whether a decrease in PTH levels, measured at the first postoperative day, can identify patients with a high risk for persistent hypoparathyroidism one year after thyroidectomy. Design Prospective multi-center cohort study. Methods Patients undergoing total or completion thyroidectomy were included. We measured PTH levels preoperatively and on the first postoperative day. Primary outcome is the proportion of patients with persistent hypoparathyroidism, defined as the need for calcium supplementation one year after surgery. Results We included 110 patients of which 81 were used for analysis of the primary outcome. At discharge 72.8% of patients were treated with calcium supplementation. Persistent hypoparathyroidism was present in 14 patients (17.3%) at one-year follow-up, all of them had a decrease in PTH >70% at the first postoperative day. These 14 were 43.8% of the 32 patients who had such a decrease. In the group of 49 patients (59.8%) without a PTH >70% decrease, none had persistent hypoparathyroidism one year after surgery (P-value <0.001). A decrease of >70% in PTH levels had a sensitivity of 100.0% (95% CI: 85.8–100.0%), a specificity of 73.1% (95% CI: 62.5–83.7%) and an area under the curve of 0.87 (95% CI: 0.79–0.94) to predict the risk for persistent hypoparathyroidism. Conclusion In our study a decrease in PTH levels of >70% after total or completion thyroidectomy is a reliable predictor for persistent hypoparathyroidism, and this should be confirmed in larger cohorts.

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Background and objective: The reported incidence of persistent hypoparathyroidism varies widely, and consensus on a definition is lacking. The objective was to evaluate the real-life incidence of persistent hypoparathyroidism by investigating a new pragmatic definition. Methods: This retrospective multicenter cohort study evaluated the effect of different definitions for persistent hypoparathyroidism on the incidence of hypoparathyroidism. In addition, risk factors for hypoparathyroidism were analyzed. Results: In total, 749 patients were included. Using the new pragmatic definition, we report an incidence of 7.9% of persistent hypoparathyroidism. When applying other commonly used definitions, incidence varied between 11.8% and 22.1%. Risk factors were parathyroid autotransplantation, presence of another surgical complication, and low postoperative serum calcium. Conclusions: Our data show that the incidence of persistent hypoparathyroidism in the literature may vary through the use of different definitions. This study indicates that a new pragmatic definition of persistent hypoparathyroidism has the potential to enable unbiased comparison between studies.