Parathyroid hormone-driven algorithms after thyroid surgery: Not one-size-fits-all

Underreported variation in parathyroid hormone (PTH) assays exists. Using quality improvement methods, we aimed to develop an institution-specific PTH-based protocol to predict hypocalcemia after thyroidectomy.

We retrospectively reviewed patients who underwent total/completion thyroidectomy. A receiver operating curve (ROC) determined postoperative PTH cut-offs predictive of hypocalcemia. The stakeholders developed PTH-driven calcium management guidelines. Post-implementation outcomes were prospectively measured.

Pre-implementation, 95 patients were assessed. PTH ≤1.5 pmol/L (14.1 pg/ml) predicted hypocalcemia (96%sensitivity), and ≥2.8 pmol/L (26.4 pg/ml) predicted normocalcemia (99%specificity) (area under curve = 0.97, SEM = 0.018). PTH on the day of and morning after surgery were identically predictive. Post-implementation, 64 patients were assessed. Hypocalcemia occurred with PTH >2.8 pmol/L in 2 cases (3.1%). Calcium over-prescribing decreased from 13.7% to 3.1% (p = 0.06). Length of stay (LOS) > 2 nights decreased from 13% to 3.1% (p = 0.05).

A PTH-driven calcium management protocol post-thyroidectomy effectively reduces unnecessary calcium replacement and LOS. Given the variability in PTH assays, each institution may need to use individual cut-offs.