Background and aims: The surgical gold standard in primary hyperparathyroidism was until recently exploration of all four parathyroid glands. Today more patients undergo minimal invasive procedures demanding more accurate preoperative localization studies. The aim of the study was to determine the positive predictive value (PPV) of parathyroid scintigraphy (PS) and to some extent ultrasonography (US), defined as the probability of finding one single adenoma on the affected side at surgery when the scans had shown one single focus.
Material and methods: Eighty-eight surgically treated patients (76 women and 12 men, 8 with multiglandular disease) were included. The PS consisted of 99mTc-sestamibi scan with dual-phase technique, both planar and SPECT imaging, followed by 99mTc-pertechnetate scan. A positive scan was defined as a single focus accumulating sestamibi. Focal lesions on US were defined as hypoechoic nodules.
Results: PS was positive in 80 patients. Seventy-nine had only one focus, of which 64 were correctly localized adenomas (PPV 81%). Forty-seven of 77 US examinations were positive. In 44 there was only one focus of which 38 were correctly localized (PPV 86%). PPV was 97% when both examinations were positive.
Conclusions: Both PS and US have acceptably high PPVs defined as the ability to predict whether or not one single focus represents a parathyroid adenoma. Concordant positive results were accompanied by a PPV close to 100%.