Risk factors for severe postoperative hypocalcaemia after operations for primary hyperparathyroidism.

Objective: To identify risk factors for severe hypocalcaemia after surgery for primary hyperparathyroidism.

Design: Retrospective study followed by a prospective study.

Setting: University hospital, Denmark.

Patients: 340 consecutive patients, operated on from 1991 to 1999, and 85 consecutive patients operated on in 2000.

Main outcome measures: Predictive value of identified risk factors.

Results: Incisional biopsy or excision of more than 2 parathyroid glands, thyroid operation together with parathyroidectomy, preoperative serum concentration of parathyroid hormone of more than 25 pmol/L, or a history of previous operations on the neck, were identified retrospectively as risk factors for severe postoperative hypocalcaemia. In the prospective study these factors showed a sensitivity of 100% (9/9), and a specificity of 25% (9/36). We found no risk of severe hypocalcaemia after parathyroidectomy in patients without these risk factors. The risk increased to 37% (7/19) if serum concentration of parathyroid hormone was more than 25 pmol/L, or if thyroidectomy was done together with parathyroidectomy.

Conclusions: Patients with no risk factors for severe hypocalcaemia can be discharged early from hospital. Special attention should be given to patients with one or more risk factors for severe hypocalcaemia.