Thallium isotope scintigraphy and ultrasonography: comparative studies of localization techniques in primary hyperparathyroidism.

Controversy exists about whether preoperative localization procedures are indicated in patients with primary hyperparathyroidism before first neck exploration. Currently, thallium subtraction scintigraphy and ultrasonography are the techniques used most frequently. This paper examines prospectively the accuracy and value of these techniques in a group of 71 patients with primary hyperparathyroidism. When considering all glands, thallium scanning produced a sensitivity of 46.6 per cent with a specificity of 91.5 per cent, compared with a sensitivity of only 21.4 per cent and specificity of 94.5 per cent for ultrasonography. Accuracy rates, for all glands, were 80 per cent and 75.7 per cent respectively. Both localization procedures were consistently ineffective in localizing adenomas weighing less than 500 mg, over 80 per cent of which went undetected by both scanning modalities. While both scans produced satisfactory results in localizing adenomas weighing more than 1 g, these adenomas should not represent a challenge to an experienced endocrine surgeon and, therefore, neither localization is recommended before first neck exploration.