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High-sensitive 2nd generation thyroglobulin immunoradiometric assay. Clinical application in differentiated thyroid
L Giovanella1, L Ceriani, S Garancini
1Laboratory of Endocrinology and Thyroid Unit, Department of Nuclear Medicine, University Hospital Ospedale di Circolo e Fondazione Macchi, Varese, Italy. lucamednuc@libero.it
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.