Comparison of techniques for thallium-201-technetium-99m parathyroid imaging.

It is impracticable to compare the variety of techniques advocated for thallium-technetium (Tl-Tc) subtraction parathyroid imaging by repeated studies in patients. We therefore carried out studies using a phantom assembly to simulate thyroid and parathyroid in the neck, containing activities of 99Tcm and 201Tl similar to those likely to be present in patient imaging. An initial study of imaging protocol confirmed that correction for scatter from 99Tcm in the 201Tl window usefully improved the image.

Pertechnetate uptake in the prediction of early outcome after radioiodine therapy.

99mTc-pertechnetate uptake was estimated 8-13 weeks after radioiodine therapy for hyperthyroidism in 132 patients in order to evaluate the usefulness of the uptake test in predicting both persisting hyperthyroidism and the early onset of hypothyroidism during the first year after therapy. The estimation was simple, the result immediately available, and its sensitivities, positive predictive value and its overall accuracy (83%) compared favourably with that of in-vitro tests, FT4I (75%) and FT3I (80%), carried out on the same occasions during the early follow-up period. Pertechnetate uptake can be a useful guide to management by promptly identifying patients likely to need further radioiodine therapy and those with transient or permanent hypothyroidism.

Factors predicting hypothyroidism in long-term follow-up after 131I therapy.

187 patients, euthyroid for more than a year after radioiodine treatment for hyperthyroidism, were studied for 10 years; 81 (43%) became hypothyroid. The incidence of hypothyroidism was lower in patients initially presenting with large thyroids (28%) or with nodular thyroids (22%) and in those without thyroid autoantibodies (31%). During follow-up, an elevated serum TSH was present in all 81 patients when they became hypothyroid (sensitivity and negative predictive value 100%), and was present for at least a year in 98% of these.

Assessment of an enhanced chemiluminescent immunometric assay for TSH in 1127 patients.

An enhanced immunochemiluminometric assay for serum TSH ('Amerlite', Amersham, Bucks, UK) was studied in 1127 patients in routine clinical practice to assess its value as a first-line test of thyroid status. Good correlation with clinical thyroid status was found in the untreated euthyroid patients, in the untreated hyperthyroid and hypothyroid patients, in pregnancy and in the sick euthyroid. However, a large proportion of clinically euthyroid patients with nodular goitre, as well as those treated by thyroidectomy, radioiodine or antithyroid drugs and those on replacement l-thyroxine showed TSH values outside the reference range.