Factors Associated With Successful Parathyroid Adenoma Localisation in Sestamibi Study—Can Change in Serum Calcium Be a Useful Indicator?

<b>Objective:</b> Primary hyperparathyroidism can be cured by the successful removal of the culpable parathyroid adenoma. Successful localisation allows the specialist surgeon to perform safer and more cost-effective focused excisions rather than exploratory surgery. This study aims to identify possible factors that predict successful adenoma localisation using technetium99m-sestamibi. <b>Design, Patients and Measurements:</b> Retrospective analysis of 159 patients undergoing parathyroid localisation with technetium99m-sestamibi SPECT/CT. Patients were classified as successful or unsuccessful localisation when compared to the surgical site of a proven adenoma following successful parathyroidectomy. Preoperative and postoperative serum parathyroid hormone (PTH), calcium and 25-hydroxyvitamin D levels and pathological size of the parathyroid adenoma were recorded. <b>Results:</b> Larger specimen volume, weight and higher preoperative PTHs were strongly associated with successful localisation. The percentage change in serum calcium (calculated as the difference between pre- and post-op calcium) was also strongly associated with successful localisation. Higher preoperative serum calcium (> 2.85 mmol/L) was also associated with successful localisation although with a reduced statistical significance. Seventy percent of patients in our cohort underwent parathyroidectomy with a serum calcium < 2.85 mmol/L, of which 92% had pathologically confirmed adenomas and 67% had successful localisation with sestamibi. <b>Conclusion:</b> The serum PTH and change in serum calcium were most strongly associated with successful localisation. The degree of hypercalcaemia was also associated with successful localisation but without as strong an association when compared to the change in calcium. Several factors influence the degree of hypercalcaemia in patients with primary hyperparathyroidism including parathyroid adenoma size, 25-hydroxyvitamin D status and the individual's baseline calcium set point. Historic information (if available) on the patient's individual baseline set point prior to developing primary hyperparathyroidism, and subsequent elevation when primary hyperparathyroidism has developed, could aid decision-making for clinicians when deciding on parathyroidectomy.