Prognostic significance of ultrasonography in diagnosis of autoimmune thyroiditis in children

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Background. Currently, ultrasound is used to diagnose autoimmune thyroiditis, the frequency of which is increasing in Ukraine and other countries. At the same time, the normal size of the thyroid is different from the World Health Organization (WHO) and literature data and depends on many factors including location. Consequently, purpose of our research is to investigate the prognostic value of ultrasound indicators to verify the diagnosis of autoimmune thyroiditis and determine the normal thyroid size in healthy children of different gender. Materials and methods. In the first stage, thyroid ultrasound was carried out in 132 children (55 boys and 77 girls) aged 11.68 ± 4.05 years with autoimmune thyroiditis. For comparison, 577 children (268 boys and 309 girls) aged 11.49 ± 4.11 years without thyroid pathology were selected. In the second stage, thyroid ultrasound was carried out in 844 children (367 boys and 477 girls) aged 1–17 years without thyroid pathology. Ultrasound examination was performed using a Toshiba Aplio 500 device with a 10.0–15.0 MHz linear transducer in the Medical Center “JMC” (Dnipro). We used parametric and nonparametric statistical methods (StatSoft Statistica for Windows). Results. Ultrasound changes of the thyroid in children with autoimmune thyroiditis were as follows: increased volume (31.06 %), decreased volume (4.55 %), thyroid isthmus thickening was recorded in 14.29 % of girls. Moreover, there were changes in the echostructure and echogenicity of the thyroid, nodules in the right (21.2 %) and left lobes (18.94 %), with increased vascular pulsation (39 %). Odds ratios (OR) and confidence intervals (CІ), sensitivity (Se), specificity (Sp), accuracy (Ac), positive predictive value (PPV) and negative predictive value (NPV) were established by ultrasound criteria. For abnormal thyroid volume, OR = 10, CІ [6.12; 16.31]; Se = 35.6 %; Sp = 94.8 %; Ac = 83.8 %; PPV = 61 %; NPV = 86.6 %. For isthmus thickening, OR = 3.52, CІ [1.84; 6.76]; Se = 12.9 %; Sp = 96 %; Ac = 80.5 %; PPV = 42.5 %; NPV = 82.8 %. For lesions in the lobes, OR = 770.1, CІ [47.11; 12784.28]; Se = 40.2 %; Sp = 100 %; Ac = 88.9 %; PPV = 100 %; NPV = 87.96 %. For increased vascular pulsation, OR = 247.06, CІ [33.86; 1816.63]; Se = 29.6 %; Sp = 99.8 %; Ac = 87.2 %; PPV = 97.5 %; NPV = 86 %. The Spearman correlation analysis demonstrated a strong monotonic relationship between thyroid volume and body weight (R = 0.78), and height (R = 0.77), and age (R = 0.70), p < 0.05. The Spearman’s correlation coefficient for thyroid volume and body mass index showed a moderate strength monotonic relationship (R = 0.55), p < 0.05. The Spearman’s correlation coefficient for thyroid volume and body surface area indicated a moderate strength monotonic relationship (R = 0.67), p < 0.05. The benefit of this study is that children of all genders had higher upper limits (97th percentile) of normal thyroid volume than the WHO data in 2007, but corresponded to the findings of scientists from Japan (Fukushima). And only in girls with a body surface area of more than 1.7 m2, the thyroid volume was larger and similar to normal for women. The median thyroid volume of children, regardless of gender, was close to that obtained by scientists from Poland and China. These features should be considered when assessing thyroid volume in children. There is also a need to develop the value tables and sigma deviations of thyroid volume in healthy children taking into account gender, age and body surface area both in individual countries and large cities. Conclusions. Ultrasound signs of autoimmune thyroiditis such as abnormal thyroid volume, isthmus thickening, lesions in the lobes, increased vascular pulsation had a low sensitivity and high specificity. Therefore, ultrasonography as a non-invasive diagnostic method is more useful for conducting screening studies in children to verify the diagnosis of autoimmune thyroiditis. Thyroid volume values in healthy children, taking into account gender, age and body surface area, differed from the WHO indicators, and a comparative analysis of the literature data considering the place of residence of the examined children indicated the need to use regional indicators of the normal size of the thyroid gland.