RESUMEN
AIM: In patients with recurrent primary hyperparathyroidism (pHPT) or preceding thyroid operation, scintigraphic localization of the pathological parathyroid gland is sometimes unsuccessful. Reason for diagnostic failure, and its clinical relevance is poorly understood. METHODS: This retrospective observational study in patients suffering from a pHPT evaluated independent predictors of a negative preoperative scintigraphy (SC) result, and its relevance for intraoperative outcome using logistic regression analysis. RESULTS: Among 86 pHPT patients scheduled for parathyroid operation, 63 (73%) had a history of a preceding thyroid or parathyroid operation. Preoperative SC could not identify an adenoma in 30 patients (34.9%), and in 12 patients (14.0%), the surgeon was subsequently unable to localize abnormal parathyroid tissue. Preoperative parathyroid hormone concentration was the only significant independent predictor of a negative SC finding (non-linear and indirect association). Independent from surgical history, an unsuccessful intraoperative focus localization was exclusively predicted by preoperative ultrasonographic (US) and SC findings (OR per diagnostic category 2.98; 95%-CI 1.03-8.58, p=0.043, and OR 2.26; 95%-CI: 1.10-4.63, p=0.027, respectively). Compared to exclusive US, however, the combination of SC and US significantly increased the sensitivity and predictive power to identify patients at a high risk for a complicated surgical procedure. CONCLUSION: In patients before parathyroidectomy, a low preoperative parathyroid hormone concentration is significantly associated with a high likelihood for a negative SC finding. Combining US with SC before operation significantly increases the chance to identify patients prone to negative intraoperative findings.