Introduction: Accurate pre-operative localisation of parathyroid adenomas allows appropriate selection of patients for minimally invasive parathyroidectomy (MIP).
Methods: Retrospective review of patients with confirmed biochemical primary hyperparathyroidism who underwent both localisation ultrasound (performed by a single operator) and sestamibi scintigraphy (majority performed at a single practice with 99mTc-pertechnetate subtraction) over the period 2010 to 2013. Adenoma localisation was confirmed at parathyroidectomy. Conditions known to predispose to multigland hyperplasia were excluded. Results were compared to a previous audit of period 2005–2009.
Results: 139 patients were identified, with average age of 66 years. 78% were female. 62% had mild primary hyperparathyroidism (corrected calcium < 2.75mmol/), while 8% had severe disease (calcium >3mmol/L). The sensitivity of ultrasound to detect any abnormality ‘possibly consistent’ with an enlarged parathyroid was 85%, with a positive predictive value (PPV) for adenoma at that location of 92%. When ultrasound imaging was considered ‘highly likely’ to show an adenoma, sensitivity was 70%, with a PPV of 98%. Sensitivity of scintigraphy to detect any abnormality ‘possibly consistent’ with parathyroid adenoma was 81%, with a positive predictive value of 97% at that site. Limiting scintigraphy results to those ‘highly likely’ to show parathyroid adenoma gave a sensitivity of 58%, but PPV of 100%. 92 cases had a concordant abnormality on both ultrasound and scintigraphy (sensitivity 69%) with a PPV for adenoma at that site of 100%. In this group, 69 patients underwent MIP with 67 cured. When compared to past audit data, sensitivity of both techniques improved from 67% to 85% for ultrasound and 74% to 81% for scintigraphy.
Conclusions: Parathyroid ultrasound and sestamibi scintigraphy are complementary techniques to localise parathyroid adenomas pre-operatively. Concordant abnormalities on both modalities improves confidence with patient selection for MIP. There was evidence of improvement in localisation technique over time.