A comparison of serum thyroglobulin measurements and whole body 131I scanning in the management of treated differentiated thyroid carcinoma.

Serum thyroglobulin levels were measured by a sensitive radioimmunoassay in 76 patients whose differentiated thyroid carcinoma had been treated by surgery with or without subsequent administration of radioactive iodine (131I). Examination of the results of 105 concomitant whole body 131I scan results and serum thyroglobulin levels showed a high degree (83.8%) of concordance between these two techniques. A significant correlation (r = 0.670, p less than 0.001) was found between serum thyroglobulin levels and quantitative 131I uptake in the neck and/or metastases in 42 patients in whom this was measured. Although a high degree of congruence was found between the results of 131I scans and the presence or absence of circulating thyroglobulin, 13 patients with negative scans using conventional doses of 131I had measurable levels of thyroglobulin. Eight of these patients had or subsequently developed evidence of residual thyroid tissue or metastatic carcinoma. The measurement of serum thyroglobulin levels in patients previously treated for differentiated carcinoma offers a more convenient and more sensitive method of detecting residual normal or neoplastic thyroid tissue than does whole body scanning in 131I.