Introduction The most common postoperative complication of total thyroidectomy is hypocalcemia, usually monitored using serum parathyroid hormone and calcium values. Objective To identify the most accurate predictors of hypocalcemia, construct a risk assesment algorithm and analyze the impact of using several calcium correction formulas in practice. Methods A prospective, single-center, non-randomized longitudinal cohort study on 205 patients undergoing total thyroidectomy. Parathyroid hormone, serum, and ionized calcium were sampled post-surgery, with the presence of symptomatic or laboratory-verified asymptomatic hypocalcemia designated as primary outcome measures. Results Parathyroid hormone sampled on the first postoperative day was the most sensitive predictor of symptomatic hypocalcemia development (sensitivity 80.22%, cut-off value ≤2.03 pmol/L). A combination of serum calcium and parathyroid concentration sampled on the first postoperative day predicted the development of hypocalcemia during recovery with the highest sensitivity and specificity (94% sensitivity, cut-off ≤2.1 mmol/L, and 89% specificity, cut-off ≤1.55 pmol/L, respectively). The use of algorithms and correction formulas did not improve the accuracy of predicting symptomatic or asymptomatic hypocalcemia. Conclusions The most sensitive predictor of symptomatic hypocalcemia present on the fifth postoperative day was PTH sampled on the first postoperative day. The need for algorithms and correction formulas is limited.

Keywords: calcium; hypocalcemia; parathyroid hormone; risk assessment; total thyroidectomy.

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