Endocrine Abstracts

Preoperative localization of the pathological parathyroid gland is critical in the clinical evaluation of patients with primary hyperparathyroidism (PHP) before surgical resection. Unfortunately, scintigraphy nor ultrasound-guided FNAB do not show enough accuracy in this respect, especially in patients with concurrent thyroid pathology.

The aim of the investigation was to assess the usefulness of measurements of PTH concentration in FNAB washouts (PTH-FNAB) in diagnosing PHP in patients with thyroid nodules or chronic thyroiditis. The study included 50 patients with a focal lesion that was suggestive in ultrasonography for parathyroid gland, 40 patients with clinical and/or biochemical picture of PHP and ten patients with a suspicion for parathyroid incidentaloma. Simultaneously biopsied thyroid nodules were the internal controls.

Mean serum PTH concentration was 310.9±393.9 pg/ml (mean±SD). Positive PTH-FNAB (PTH-FNAB concentration – after dilution of a specimen in 1 ml 0.9% NaCl – higher than in serum) was observed in 40 patients (80.0%). Mean positive PTH-FNAB±SD was 2822.41±2061.29 pg/ml. Mean negative PTH-FNAB was significantly lower (12.3±8.7 pg/ml, P<0.0002) and similar to that in the internal controls. Negative predictive value (NPV) of classical FNAB vs PTH-FNAB was 26.5%, NPV of scintigraphy vs PTH-FNAB was 46.2%, NPV of PTH-FNAB vs scintigraphy was 66.7%. No false negative result of PTH-FNAB vs classical FNAB was noted. Lower frequency of positive PTH-FNAB was observed when the thickness of the thyroid lobes was >20 mm (50.0 vs 87.5%, P<0.05) and when the thickness of a lesion suspected for parathyroid pathology was ≤5 mm (66.7 vs 93.3%, P<0.05). The negative influence of chronic thyroiditis was less marked (73.9 vs 85.2%). Surgical removal of the parathyroid lesion was performed in 20 patients (five cases of hyperplasia, 14 adenomas, and one parathyroid cancer). No false positive PTH-FNAB was observed in that group and only one false negative result was noted in a patient with large nodular goitre.

Measurement of PTH concentration in the FNAB washouts allows to identify pathological parathyroids in patients with thyroid abnormalities more effectively than scintigraphy and classical ultrasound-guided FNAB.