The diagnostic value of parathormone washout in Tc-99m MIBI negative primary hyperparathyroidism cases

Abstract

Aim: To determine the sensitivity and positive predictive value (PPV) of the measurement of parathormone (PTH) in fine needle aspiration (FNA) washout fluid, in the preoperative localization of hyperfunctional parathyroid lesions. Methods: Medical records of patients diagnosed with primary hyperparathyroidism (PHPT) in our clinic between 2016-2020 were retrospectively evaluated. Thirty-six patients with PHPT who underwent preoperative FNA-PTH washout procedure were included in the study. FNA-PTH washout was only performed in patients with negative technetium-99m methoxy isobutyl isonitrile / single photon emission computed tomography (Tc-99m MIBI/SPECT) imaging. It was accepted to be higher than plasma PTH level as positive cut-off value for PTH washout in determining parathyroid lesions. Sensitivity, PPV, false positive, false negative and diagnostic accuracy values of PTH washout were calculated. Results: PTH washout was false positive in 2 cases, false negative in 1 case and true positive in 33 cases. In the discrimination of true parathyroid lesions, the sensitivity of PTH washout was calculated as 97.05%, PPV 94.29% and diagnostic accuracy 91.67%. PTH washout levels correlated positively with plasma PTH and parathyroid lesion volüme (respectively, r=0.347, p=0.041 ve r=0.356, p=0.036). All patients tolerated the FNA-PTH flushing procedure well and no complications developed afterwards. Conclusion: The FNA-PTH washout is a safe and useful method to localise parathyroid lesions in PHPT patients with negative Tc-99m MIBI/SPECT imaging.