Usefulness of PTH measurements in FNAB washouts in the identification of pathological parathyroids - analysis of the factors that influence the effectiveness of this method

Introduction: The aim of this investigation was to assess the usefulness of the measurement of PTH concentration in the material obtained during FNAB (PTH-FNAB) in the identification of pathological parathyroids in patients with frequently coexisting thyroid abnormalities (nodular goitre, chronic thyroiditis, previous thyroidectomy). Additionally, the influence of the size of goitre, parathyroid localisation and size on the results of PTH-FNAB measurement was examined. Material and methods: Fifty patients with primary hyperparathyroidism and sonographically detected focal lesion that was suggestive of parathyroid gland were included in this study. PTH-FNAB results were correlated with the outcome of routine cytological examination and biochemical indices of hyperparathyroidism, SPECT-CT (33 patients) and histopathological examination (20 patients). Results: Positive PTH-FNAB was observed in 80% of patients, and in more than 70% of persons with non-diagnostic smears or smears 'contaminated' with thyroid follicular cells. In the group of operated patients, sensitivity of PTH-FNAB (95.0%) was higher than SPECT-CT (64.3%, p < 0.05). Presence of nodular goitre and/or chronic thyroiditis exerts a two times stronger negative effect on percentage of negative results of SPECT-CT than of PTH-FNAB. On the other hand, lower frequency of positive PTH-FNAB but not SPECT-CT was observed when the thickness of the thyroid was >= 20 mm (50% v. 87.5%, p < 0.05) and when the thickness of a lesion suspected of parathyroid pathology was <= 5 mm (66.7% v. 93.3%, p < 0.05). Conclusions: In patients with thyroid abnormalities, PTH-FNAB measurements show advantages over routine biopsy and SPECT-CT in the identification of typically located pathological parathyroids.