Prospective evaluation of intra-operative quick parathyroid hormone assay as an early predictor of post thyroidectomy hypocalcaemia

Abstract

Background: Hypocalcaemia following total thyroidectomy is a major contributing factor in delayed hospital discharge and dissuading surgeons from day care thyroidectomy. We prospectively evaluated the utility of Intra-operative serum quick parathyroid hormone level measurement twenty minutes after total thyroidectomy in predicting post-operative hypocalcemia.

Material and methods: Prospective longitudinal study which included patients undergoing total thyroidectomy for benign or malignant thyroid disorders at SGPGIMS, Lucknow, India from November 2013 to February 2015. Patients who received calcium prophylaxis were excluded from the study. Intraoperative serum quick PTH level measurements were done twenty minutes after resection of thyroid. Serum calcium levels were estimated preoperatively and on three consecutive post operative days. Calcium supplementation was started in patients with symptomatic hypocalcemia.

Results: The study included 100 patients with a mean age of 41 years, range 17-72 years. 48 patients had Euthyroid multinodular goitre, 10 patients grave's disease and 42 patients had differentiated thyroid cancer. Total thyroidectomy was performed in 88 patients, total thyroidectomy with lymph node dissection in 12 patients. Post-operatively 23% patients experienced symptomatic hypocalcemia. The IOPTH level of 9 pmol/L, twenty minutes after total thyroidectomy, had the highest sensitivity and specificity of 92% and 83% respectively in predicting post-operative hypocalcemia.

Conclusion: Parathyroid hormone assay twenty minutes after thyroidectomy is an accurate and reliable means of predicting clinically relevant hypocalcemia. Patients with PTH values greater than 9 pmol/L twenty minutes after thyroidectomy, can be safely discharged on the same postoperative day as the probability of life threatening hypocalcemia is unlikely.

Keywords: Intra-operative; PTH; Post operative hypocalcemia; Thyroidectomy.