Imaging localization strategies in primary hyperparathyroidism

Parathyroid glands exhibit a notable anatomical variability, complicating preoperative localization. Minimally invasive parathyroidectomy ideally requires two concordant imaging tests. This study aims to evaluate the degree of concordance of the different tests available with surgical findings and to create an algorithm to discern the order in which these tests should be performed.

This prospective study included 93 patients with primary hyperparathyroidism (PHP) undergoing 99mTc-sestamibi SPECT/CT and cervical ultrasound. Discordant cases underwent secondary imaging (contrast-enhanced ultrasound [CEUS], CT, MRI, or 18F-choline PET/CT) based on endocrinologist criteria. Sensitivity, positive predictive value (PPV), accuracy, and Cohen's Kappa index (k) relative to surgical outcomes were calculated for each modality.

Of the 93 patients studied, 46 (49.5 %) were included in Group A (concordant location between 99Tc-sestaMIBI and ultrasound) and 47 (50.5 %) in Group B (discordant initial tests). Overall, 99mTc-sestamibi SPECT/CT showed κ = 0.55 (p < 0.001), while ultrasound demonstrated κ = 0.67 (p < 0.001). In Group B, imaging tests yielded the following κ values: CEUS = 0.64 (p < 0.001), 18F-choline PET/CT = 0.62 (p = 0.013), CT = 0.54 (p = 0.002), ultrasound = 0.43 (p < 0.001), 99mTc-sestamibi SPECT/CT = 0.34 (p = 0.013) and MRI = 0.14 (p = 0.145).

In patients with PHP with surgical criteria in whom initial scintigraphy and ultrasound were concordant, both tests showed moderate concordance with surgery. In discordant cases, CEUS showed the greatest concordance with surgery, followed by 18F-choline PET/CT. Thus, we propose an algorithm in which localization tests should be performed in a certain order based on the performance of each test in each possible scenario.