The value of ultrasonography in predicting autoimmune thyroid disease

Ultrasonography (US) may demonstrate a diffuse reduction in thyroid echogen icity (low-amplitude echoes) in autoimmune thyroid disease (AITD), which in cludes chronic lymphocytic thyroiditis and Graves' disease, as well as in s ubacute thyroiditis. The reported occurrence of this finding in AITD varies from 19% to 95%. To assess the validity of diffuse reduction in thyroid ec hogenicity as a predictor of AITD, 3,077 patients referred for US of the th yroid were examined prospectively with regard to reduced versus normal thyr oid echogenicity. The most frequent reasons for referral were goiter, thyro id dysfunction, neck discomfort, and/or difficulty in swallowing. Ultrasono graphy demonstrated diffuse reduction in thyroid echogenicity in 485 patien ts. Of these, 452 patients had available records of fine-needle aspiration biopsy (FNAB), and were included in the study. From the remaining patients, with normal thyroid echogenicity, 100 consecutive patients were selected a s controls. In 411 of the 452 study patients (90.9%) there was at least one laboratory finding consistent with possible AITD: cytology indicating lymp hocytic thyroiditis, 287 of 363 patients (79.1%) with diagnostic specimens; elevated levels of peroxidase antibodies (TPOAb), 225 of 337 (66.8%); elev ated thyrotropin (TSH) levels, 290 of 450 (64.4%); or low TSH levels, 79 of 450 (17.6%). The final diagnosis was: chronic autoimmune (Hashimoto's) thy roiditis in 352 patients; Graves' disease in 47 patients; subacute (granulo matous) thyroiditis in 7 patients; toxic nodular goiter in 3 patients; and toxic adenoma in 2 patients. In the remaining 41 patients, those without la boratory results consistent with AITD, the final diagnosis was colloid goit er in 37 and thyroid cancer in 4 patients. In the 100 controls, laboratory results were consistent with possible AITD in 14 patients: elevated TPOAb l evels in 5 of 49 patients with retrieved antibody results; lymphocytic thyr oiditis in 2 patients; elevated TSH levels in 2 patients; and low TSH level s in 2 patients. In these controls, the final diagnosis was: chronic autoim mune thyroiditis in 7;toxic nodular goiter in 6 patients, and toxic adenoma in 1 patient. The corresponding positive and negative predictive values of reduced thyroid echogenicity as an indicator of AITD were 399 of 452 (88.3 % [95% CI, 85% to 91%]), and 93 of 100 (93.0% [95% CI, 88% to 98%]), respec tively. Thus, diffuse reduction in thyroid echogenicity was a valid predict or of AITD.