Parathyroid scintigraphy in primary hyperparathyroidism: comparison between double-phase and subtraction techniques and possible affecting factors.

Parathyroid scintigraphy is superior to other imaging techniques in detecting hyperfunctioning parathyroid glands. It is mainly performed using double-phase or dual-tracer subtraction methods. Neither of the techniques is perfect and different protocols are being used. We aimed to evaluate the accuracy of double-phase and subtraction methods in detecting abnormal gland as well as the potential effects of coexisting thyroid disease and clinical-laboratory data. We considered patients with primary hyperparathyroidism who underwent parathyroid surgery, after a parathyroid scintigraphy between April 2015 and February 2017. Sixty-eight patients were included; in 45 cases (66.2%), a thyroid disease was coexistent. Diagnostic performances of the two techniques were compared. The effect of thyroid disease and clinical-pathological data on examination interpretation was considered. Double-phase scintigraphy showed higher sensitivity and accuracy in detecting the exact abnormal gland compared to the digital subtraction (90% and 75% vs. 76% and 66%, respectively). For double-phase technique, sensitivity and accuracy were higher in cases with no thyroid disease when compared to those with thyroid disease (92% and 86% vs. 88% and 69%, respectively). Similarly, for digital subtraction, sensitivity and accuracy were higher in the absence of thyroid disease compared to their presence (84% and 79% vs. 70% and 58%, respectively). There was no significant variation in the performance of both techniques, considering clinical-laboratory data. Double-phase scintigraphy has been more accurate than digital subtraction. The presence of thyroid disease could be a possible limit, affecting the subtraction more than the double-phase technique. Clinical data did not influence the scintigraphic outcome.