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Intact parathyroid hormone value on the first postoperative day following total thyroidectomy as a predictor of permanent hypoparathyroidism: a retrospective analysis on 426 consecutive patients.

INTRODUCTION
Hypoparathyroidism represents a common complication following total thyroidectomy. To date, there is still no reliable and immediate postoperative parameter to establish which patients with postsurgical hypoparathyroidism will develop permanent hypoparathyroidism. The main purpose of the present study was to assess whether the intact parathyroid hormone (iPTH) value on the first postoperative day is a good predictor of permanent hypoparathyroidism.


MATERIAL AND METHODS
Patients undergoing thyroidectomy in our unit between March 2018 and January 2020 were analysed. According to the iPTH value on the first postoperative day and on the basis of the detection threshold of the iPTH test used, patients were divided into two groups: Group A (iPTH ≥ 4.6 pg/mL) and Group B (iPTH < 4.6 pg/mL, undetectable).


RESULTS
In total 426 patients were included: 364 in Group A and 62 in Group B. Permanent hypoparathyroidism occurred in 3 (0.82%) patients from Group A and in 26 (41.94%) from Group B (p < 0.001). When iPTH levels were < 4.6 pg/mL on the first postoperative day the sensitivity for the prediction of permanent hypoparathyroidism was 89.66%, the specificity was 90.93%, the positive predictive value (PPV) was 41.94%, the negative predicitive value (NPV) was 99.18% and the accuracy was 90.85%.


CONCLUSIONS
An iPTH value < 4.6 pg/mL on the first postoperative day following total thyroidectomy has proven to be a good parameter for early identification of patients at high risk for permanent hypoparathyroidism. Moreover, we want to underline that in our experience no patient with an iPTH level > 6.5 pg/mL developed this complication.