Objectives Recently, it is frequently proposed that diagnostic 131-Iodine Whole-Body Scan (DWBS) may be avoided in patients with undetectable levels of serum thyroglobulin (Tg) off L-thyroxine, and that Tg levels are sufficient as the sole surveillance test in low risk Differentiated Thyroid Carcinoma patients (DTC), particularly if the first post 131-Iodine treatment follow up DWBS, Tg and Tg antibodies (Tg Ab) are negative. The aim of the current study was to evaluate the role of DWBS in follow up of DTC.

Methods Follow up DWBS and serum Tg levels of 52 consecutive patients (44 papillary thyroid carcinoma, and 8 Follicular thyroid carcinoma including one Hürthle cell variant) were reterospectively evaluated. Scans were acquired using a high energy collimator fitted to Phillips Forte dual head gamma camera, 48 hours after an oral administration of 2.5 - 3.9 mCi I-131 capsule. An Immunoluminescent assay (Bioscientia, Ingelheim, Germany) was used for serum Tg determination. DWBS and Tg assay were performed following suspension of L-thyroxine for one month (TSH > 30 µIU/ml) in 45 patients and following rhTSH stimulation in 7 patients.

Results Of the 52 studied patients, 4 were excluded because of high serum Tg Ab. Of the remaining 48 patients, 11/48 (22.9%) had positive DWBS but negative Tg, 6/48 (12.5%) had negative DWBS but positive Tg, and 31/48 (64.6%) had concordant DWBS and Tg results.

Conclusions In follow up of DTC, the results of DWBS and Tg were discordant in more than one third of patients. Our findings suggest that in follow up of DTC, DWBS still provides useful information, and both DWBS and serum Tg should be evaluated