Abstract
Autoimmune thyroid disease (AITD) is the most common organ specific autoimmune disorder resulting in dysfunction of the thyroid gland (1). The presently accepted classification of AITD includes chronic autoimmune thyroiditis or Hashimoto’s thyroiditis (HT) and its variants (painless postpartum and sporadic thyroiditis), autoimmune atrophic thyroiditis or primary myxoedema and Graves’ disease (GD) (2). Thyroid ultrasonography has become an important non-invasive diagnostic method for the evaluation of thyroid function. The main characteristics evaluated with it are the grayscale sonography parameters, inclyding thyroid volume, echotextute and echogenecity, and the color flow Doppler sonography (CFDS) parameters, including intraparenchymal blood flow and blood flow at the inferior thyroid artery (ITA) (34,35). Although grayscale sonographic characteristics have been widely used for the diagnosis of AITD, their predictive value has not been directly compared to the corresponding of Dopple ...
Autoimmune thyroid disease (AITD) is the most common organ specific autoimmune disorder resulting in dysfunction of the thyroid gland (1). The presently accepted classification of AITD includes chronic autoimmune thyroiditis or Hashimoto’s thyroiditis (HT) and its variants (painless postpartum and sporadic thyroiditis), autoimmune atrophic thyroiditis or primary myxoedema and Graves’ disease (GD) (2). Thyroid ultrasonography has become an important non-invasive diagnostic method for the evaluation of thyroid function. The main characteristics evaluated with it are the grayscale sonography parameters, inclyding thyroid volume, echotextute and echogenecity, and the color flow Doppler sonography (CFDS) parameters, including intraparenchymal blood flow and blood flow at the inferior thyroid artery (ITA) (34,35). Although grayscale sonographic characteristics have been widely used for the diagnosis of AITD, their predictive value has not been directly compared to the corresponding of Doppler parameters (23). Several qualitatively classifications of intrathyroidal vascular patterns have been used in clinical practice (94). CFDS has been used for the differential diagnosis of HT and GD, although without the application of receiver operating characteristic (ROC) curves. As a result, the widespread use of published cutoff points for the CFDS parameters still remains underpowered. The purpose of this thesis was to determine the sensitivity and specificity of grayscale and CFDS parameters for the diagnosis of AITD overall and the differential diagnosis of HT from GD, while performing quantitative analyses of thyroid vascularity and echogenicity and using ROC analyses. All these characteristics were evaluated in 2 studies. In the first study, including 111 participants, high sensitivity CFDS was used to estimate the thyroid intraparenchymal vascularity with a semi-quantitive method, the vascularity index (VI), in 31 euthyroid patients with HT, 33 hypothyroid patients with HT,13 hyperthyroid patients with GD, and in 34 healthy controls. Compared to healthy controls, patients with AITD had higher mean VI of both the right and the left thyroid lobe (TL) (p<0.001). The sensitivity of left TL VI values greater than 5.57% (the best cut-off value of the ROC curve) for the diagnosis of AITD is 80.8% and the specificity is 85.3%. Right TL VI values greater than 14.75% have 84.6% sensitivity and 86.2% specificity for the differential diagnosis among patients with HT or GD. We compared the sensitivity and specificity of VI (%) to the corresponding of reduced echogenecity and irregular echo pattern and found the first to be more specific, but less sensitive for the diagnosis of AITD. We also found similar VI (%) values in patients seropositive for both anti-TPO and anti-Tg, as compared to seropositive patients for anti-TPO or anti-Tg.In the second study, a consecutive series of 153 patients (70 euthyroid and 54 hypothyroid patients with HTand 29 patients with GD), and 48 age- and sex-matched healthy control participants were evaluated with grayscale and CFD sonography. The sensitivity and specificity of a number of sonographic parameters for AITD diagnosis and for differential diagnosis HT from GD was assessed while using ROC analyses. An irregular echo pattern in the thyroid parenchyma has 92.8% sensitivity for the diagnosis of AITD, and a left ITA peak systolic velocity (PSV) greater than 26.11cm/s has 91.7% specificity. Hypoechogenecity remains one of the main characteristics of AITD, as it was found that left TL hypoechogenecity index (HI) values greater than 0,9 has 91,6% specificity for the diagnosis of AITD. Of 8 patients with HT and normal grayscale sonographic characteristics, 6 had a left ITA PSV greater than 26.11 cm/s. A left ITA PSV greater than 61.65cm/s has 82.8% sensitivity and 86.9% specificity for differentiating HT from GD, being tne most specific index for this purpose.In conclusion, the results of this thesis indicate than the left ITA PSV is the most accurate sonographic parameter for the diagnosis of AITD and for the differential diagnosis of HT from GD. Measurement of the ITA PSV could be used in patients with a normal grayscale sonographic appearance and inconclusive clinical and biochemical parameters to substantiate the diagnosis of AITD.
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