Effects of sample storage and diluents in the reliability of thyroglobulin measurement in the washout of fine needle aspirates.

Objective: To evaluate two variables affecting Thyroglobulin stability in the washout of fine needle aspiration biopsies of thyroid nodules and metastatic lymph nodes.

Materials And Methods: Thyroglobulin stability after storage at -20 °C up to 14 days was studied in washout performed with normal saline solution and further dilutions with normal saline solution from five metastatic thyroid nodes and six benign thyroid nodules. We also studied thyroglobulin stability in diluents compared with normal saline solution: 4% bovine serum albumin in normal saline solution and diluents free from thyroglobulin or Calcitonin or parathyroid hormone in paired and simultaneous thyroglobulin measurements of washout dilutions from 5/6 benign thyroid nodules and 2/5 metastatic lymph nodes.