A Protocolled Implementation of Upfront Ultrasound, A Stepwise Pre-Operative Imaging Regimen in Primary Hyperparathyroidism.

OBJECTIVE: To evaluate the sensitivity of a stepwise preoperative imaging regimen for patients with primary hyperparathyroidism. STUDY DESIGN: Prospective cohort study. SETTING: A high-volume tertiary referral center for parathyroidectomy. METHODS: Patients with primary hyperparathyroidism referred for parathyroidectomy underwent surgeon-performed ultrasound as the primary preoperative imaging examination. The diagnostic confidence of the examiner on a scale from 0 to 3 determined whether additional imaging was acquired. If ultrasound identified an enlarged parathyroid gland with certainty (score 3), the patient was booked directly for surgery. If the confidence score was <3, the patient underwent either parathyroid scintigraphy or 18F-choline PET/CT. The gold standard was the intraoperative location of pathological parathyroid glands combined with biochemical cure ≥6 months after surgery. The primary endpoint was the sensitivity of the stepwise imaging regimen per patient, irrespective of the number of acquired imaging modalities. Secondary endpoints were the sensitivity per gland and the sensitivity of the imaging regimen if the cut-off for additional imaging had been a confidence score of 1 or 2. RESULTS: Upfront ultrasound spared 49 of 99 patients (49.5%) from additional imaging and correctly localized ≥1 pathological parathyroid gland in 98.0% of patients [95% CI 92.9-99.8]. The per-gland sensitivity was 92.5% [95% CI 84.8-1.0]. When changing the cut-off to a confidence score of 2, the per-patient sensitivity remained 98.0% [95% CI 92.9-99.8]. CONCLUSION: Our study demonstrates that a stepwise imaging regimen based on upfront ultrasound by an experienced examiner can substantially reduce the number of radiation-based supplemental scans, while maintaining a high sensitivity.