Hashimoto's thyroiditis (HT) is one of the most common causes of goiter and hypothyroidism. Diffuse low echogenicity has been reported in autoimmune thyroid diseases. In this prospective study we aimed to compare diagnostic value of sonography with serum thyroid autoantibody levels in biopsy proven HT. Sixty-one patients, aged 20-87 years, that had suspicious sonographic findings for HT were in cluded in to the study. Serum Tg-Ab and TPO-Ab, thyroid function tests, erythrocy te sedimentation rate, WBC count and thyroid scintigraphy were carried out and fine needle aspiration biopsies (FNAB) from each lobe were performed on all patients.
According to FNAB results 53 out of 61 patients were diagnosed as HT. Of all FNAB positive patients, Tg-Ab and TPO-Ab were found false negative in 24 (45%) and 13 (24%) patients, respectively. Among FNAB positive patients, only Tg-Ab was positive in 3 and only TPO-Ab was positive in 13 patients. Both Tg-Ab and TPO-Ab were found to be false negative in 10 patients with HT. US was the only positive test suggesting HT in these patients.
In conclusion, positive sonographic findings are highly suggestive of HT even in patients that have normal thyroid autoantibody levels. FNAB should be performed for definite diagnosis in these patients.
Keywords: Hashimoto's thyroiditis, ultrasonography, thyroid autoantibodies