Novel Method in Performing PTH Washout for Localizing Parathyroid Adenoma: Case Report & an Institute Experience in Qatar

Introduction: Primary hyperparathyroidism (PHPT) is a common cause of hypercalcemia and mostly caused by benign solitary benign adenoma (80 to 85 %). Definite treatment is the surgical removal. The most commonly used diagnostic modalities are Sestamibi scan and neck ultrasound (US) which can be inconclusive in some cases. Parathyroid hormone (PTH) washout obtained with ultrasound guided FNA may be useful to accurately localize the adenoma. In our study we describe a novel method for PTH washout. Methods: First, blood samples are drawn from the patient’s peripheral vein and placed in two yellow top tubes (3 ml of blood in each tube). 1 ml of normal saline (NS) will be add to Tube # 1 (Control tube). The suspected parathyroid lesion aspirate is obtained via US guided FNA. It is washed in 1 ml of NS and added to tube #2 (PTH washout tube). Both tubes are sent to our local laboratory for PTH assay. The ratio of PTH in PTH washout tube to control tube (PTH W/C ratio) is calculated and considered positive if more than 2. Results: Total 16 patients (12 females and 4 males) underwent the PTH washout procedure. All patients had PHPT. Out of 16 patients, 13 had inconclusive Sestamibi scan while 3 patients didn’t have the scan due to pregnancy. PTH W/C ratio was positive in 13 patients (ruled in) and negative (ruled out) in 3 patients. All patients underwent parathyroid surgery. The operative findings and pathology report were consistent with PTH W/C ratio findings. i.e. parathyroid hypercellularity was found in all the 13 patients ruled in by PTH W/C ratio. Post-surgery, biochemical parameters normalized in all. Conclusion: PTH washout is an important tool in localizing parathyroid lesion in PHPT when Sestamibi scan cannot be done or if it is inconclusive. PTH W/C ratio can be performed with our novel method to accurately localize the PTH lesion and improve surgical outcome.