Predicting risk factors of postoperative hypocalcemia after total thyroidectomy: is safe discharge without supplementation possible? A large cohort study.

Purpose: With increasing economic pressures to shorten the length of hospital stay, there has been much recent interest in studying risk factors for the development of postoperative hypocalcemia after total thyroidectomy. The aim of this study was to investigate whether serum calcium and/or PTH levels can predict post-thyroidectomy hypoparathyroidism.

Methods: From January to December 2014, 477 consecutive patients undergoing total thyroidectomy were included. Corrected calcemia and PTH were systematically performed on postoperative day 1/(POD1). Symptomatic patients were treated on POD1 or POD2 with calcium and vitamin D.

Results: Sixty-eight patients (14.25%) were treated for postoperative hypocalcemia. No patients with calcemia ≥ 2.16 mmol/l and PTH ≥ 1.9 pmol/l were supplemented and therefore were safely discharged on POD1 (specificity = 100%). All patients with calcemia ≤ 1.89 mmol/l were treated regardless the PTH values (n = 10) (specificity = 100%). For calcium value between 1.9 and 2.16 mmol/l with a PTH > 4.7 pmol/l, nobody was treated. With a calcemia between 1.9 and 2.16 mmol/l and a PTH > 1.9 pmol/l, 44 patients did not develop any symptom. ROC curve analysis showed that combination of Cac = 2.16 mmol/l and iPTH = 4.7 pmol/l provided a sensitivity of 97.06% and a specificity of 76.53% (p < 0.0001). We therefore propose an algorithm that would allow to 70% of patients could have been discharged on POD1 without risk of hypocalcemia or overtreatment.

Conclusion: Combination of corrected calcemia and PTH on POD1 can efficiently predict hypocalcemia and be integrated into clinical practice for personalizing lengths of hospitalization and appropriate treatment.

Trial Registration: ClinicalTrials.gov PRS. Unique Identifying number or registration ID: NCT04372225.