Early detection of hypocalcemia after total/completion thyroidectomy: routinely usable algorithm based on serum calcium level

The purpose of this prospective bicentric study was to investigate the course of serum calcium (Ca) and phosphorus (Phph) after total/completion thyroidectomy to establish a reliable and cost-effective strategic algorithm to detect patients at risk for postoperative hypocalcemia.

This observational study included 136 patients. Serum Ca and Phph levels were preoperatively and postoperatively recorded 6, 12, 20, and 48 h (H) after skin closure. Criteria for hypocalcemia were postoperative Ca levels ≤1.9 mmol/L at any time point and/or patients experiencing symptoms of hypocalcemia. Postoperative Ca supplementation was never given before H20 assay. Ca levels and their differences between time points were compared.

Twenty-four percent of patients experienced hypocalcemia. At H12 and H20, the rates of patients with Ca levels ≤1.9 mmol/L were similar and larger than at H6 (p < 0.001). The H20-preoperative difference had the best area under the ROC curves (value = 0.87), and a difference ≤-0.3 was significantly more frequent in case of hypocalcemia (p = 0.001). The H20 assay and the difference H20-preop were consequently selected to design a new algorithm for hypocalcemia detection. Adding H48 assay in some specific cases (12.5 % of all included patients) enabled 100 % detection. Phosphorus assays were not informative in detecting hypocalcemia.

This new algorithm enables, with 100 % sensitivity and 88.4 % specificity, early detection of severe hypocalcemia after total/completion thyroidectomy. It may become a useful and cost-effective tool for safe and early patient discharge, especially if PTH assays cannot be routinely used because of their availability or cost.