Serum calcium relative decline as a predictor of post thyroidectomy hypocalcaemia

To assess the value of corrected calcium decline at 6 hours as a predictor of hypocalcaemia post total thyroidectomy by comparing it to the currently widely used intact parathyroid hormone.

A retrospective cohort study of patients who underwent total thyroidectomy from January 2016 to February 2020. Serum intact parathyroid hormone and corrected calcium data pre-operatively and 6 hours post-operatively were obtained. Receiver operating characteristic curves were used to compare corrected calcium decline at 6 hours versus 6 hours for relative intact parathyroid hormone decline as predictors of hypocalcaemia, and the area under the curve for each metric was reported.

Patients included in this analysis totalled 209. The receiver operating characteristic analysis suggested that corrected calcium decline at 6 hours has a similar predictive value to 6 hours relative intact parathyroid hormone. The areas under the curves for predicting hypocalcaemia were 0.797 for corrected calcium decline at 6 hours and 0.737 for 6 hours relative intact parathyroid hormone, but the difference (0.06) was not statistically significant.

Our results suggest that corrected calcium decline at 6 hours has a similar predictive value to 6 hours relative intact parathyroid hormone and hence has the potential to predict post-operative hypocalcaemia.