Thyroid volume influences serum calcitonin levels in a thyroid-healthy population: results of a 3-assay, 519 subjects study

Abstract Background: We aimed to assess determinants for serum calcitonin (CT) levels and to define reference ranges for different CT immunoassays integrating thyroid ultrasonography (TUS) and conventional clinical and biochemical criteria to select the reference population. Methods: Five hundred and nineteen thyroid-healthy subjects were included in this prospective cross-sectional population study. Thyroid volume was measured by TUS, while serum CT levels were measured by three different immunoassays. Results: Significant interassay differences were found and the agreement between assays was poor. CT levels were higher in males than in females in all immunoassays. Using the first two assays, both gender and thyroid volume were independent determinants for CT levels. While using the third assay, one thyroid volume was the only determinant for CT levels. Conclusions: Thyroid volume is a relevant determinant for CT levels. In the clinical practice, the difference of the thyroid sizes in males and females warrants gender-specific reference ranges.     

Thyroglobulin assay 4 weeks after thyroidectomy predicts outcome in low-risk papillary thyroid carcinoma.

BACKGROUND: Thyroidectomy followed by administration of large activities of 131I is the treatment of choice for differentiated thyroid carcinomas. Due to its good prognosis, some authors argue that papillary thyroid cancer with a diameter of up to 10 mm can be treated by surgery alone. In the new TNM classification started in 2002, the T1 group now encompasses all tumours with a diameter up to 20 mm, which widens the indications for a conservative approach. In this instance, prognostic markers are needed to better select patients before planning non-aggressive treatment. Serum thyroglobulin plays a pivotal role in thyroid carcinoma management after thyroid ablation (i.e., surgery and radioiodine) but is of limited value before these treatments. However, thyroglobulin assay performed after surgery but before radioiodine treatment has been proven to be useful in predicting the presence/absence of distant metastasis. PATIENTS AND METHODS: Our study was undertaken in patients affected by pT1 papillary thyroid carcinoma to evaluate the predictive value of post-surgery thyroglobulin assay on 1) restaging immediately after radioiodine treatment and 2) restaging at 12 months. We selected 156 patients affected by pT1 histologically proven papillary thyroid carcinoma, submitted to total thyroidectomy. Serum thyroglobulin was assayed by a specific immunoradiometric method 4 weeks after surgery, just before radioiodine administration. Cut-off levels were selected by receiver operating characteristic curve analysis. Thyroglobulin levels were compared to the results of a post-radioiodine treatment scan and 12-month restaging. RESULTS: Globally, 23 out of 156 patients showed persistent/recurrent disease (15%). Post-surgery thyroglobulin levels above 4.50 microg/L identified 94% of patients with metastasis at post-dose scan, and a level below 3.20 microg/L identified 86% and 93% of relapsed and disease-free patients at 12-month restaging, respectively. Multivariate analysis and Spearman rank correlation showed that the N-status and post-surgery thyroglobulin level are independent prognostic factors. CONCLUSIONS: The post-surgery thyroglobulin level could be systematically assayed in patients with pT1-papillary thyroid carcinoma and taken into account in planning treatment.     

High-sensitive 2nd generation thyroglobulin immunoradiometric assay. Clinical application in differentiated thyroid cancer management.

BACKGROUND: Circulating human thyroglobulin (hTG) measurements have a pivotal role in the management of patients affected by differentiated thyroid cancer (DTC). The present study was undertaken by employing a new developed high-sensitive hTG immunoradiometric assay to evaluate its diagnostic performance in patients affected by radically cured and relapsing DTC and to set the most appropriate cut-off point for DTC management. METHODS: We retrospectively selected 172 patients without signs of recurrence after primary treatment and 45 patients with recurrences from DTC. Serum samples were collected during l-thyroxine (T4) suppressive therapy (onT4) and 4 weeks after T4 withdrawal (offT4) and hTG measured by a specific high-sensitive IRMA assay (DYNOtest Tg-plus, BRAHMS Diagnostica GmbH, Berlin, Germany). Sera showing the presence of AbhTG or hTG-recovery less than 80% were excluded from the study. ROC curve analysis was performed to select the best cut-off levels and diagnostic performance of the marker evaluated. RESULTS: By using onT4 cut-off level of 0.2 ng/mL and offT4 cut-off level of 0.5 ng/mL we obtained a sensitivity/specificity/accuracy profile of 0.91/0.98/0.96 and 0.98/0.97/0.97, respectively. We found onT4-hTG false-negative results in 4 patient with local recurrence (n=2) or cervical lymph-node metastasis (n=2) while only 1 patient with local recurrence showed negative offT4-hTG. However, onT4 and offT4-hTG false-negative results were observed in 9 and 5 patients when 1.0 ng/mL cut-off level was employed. CONCLUSIONS: On the basis of our data, we conclude that DYNOtest Tg-plus assay is very effective and accurate in the evaluation of patients with DTC.     

Calcitonin measurement on fine needle washouts: Preanalytical Issues and Normal Reference Values

Calcitonin (CT) measurement on fine‐needle aspiration cytology (FNAC) washouts (FNAC‐CT) is a promising tool in the diagnosis of medullary thyroid carcinoma (MTC). Guidelines for the method with codified cut‐off are needed to use this technique in clinical routine. This study was undertaken to assess the best pre‐analytical procedure and to define a reliable reference value for FNAC‐CT. Fifty‐four patients underwent thyroid surgery, so MTC was excluded by surgical pathology examination and CT immunostains. Before surgery, FNAC‐CT was measured on 78 thyroid nodules from such 54 patients. Needles were rinsed by normal saline and specific CT‐free dilution buffer, and CT was measured by a fully automated immunochemiluminometric assay. FNAC‐CT levels were not significantly different in normal saline or specific buffer. The calculated 97.5th upper FNAC‐CT value was 8.5 pg/mL (saline) and 7.43 pg/mL (buffer), respectively. Seeing its relatively large sample size, rigorous selection criteria and inclusion of CT immunostaining of thyroid nodules, the present study provides a reliable guideline and a clinically relevant reference value for FNAC‐CT measurement in thyroid nodules. Diagn. Cytopathol. 2013. © 2011 Wiley Periodicals, Inc.