C-TI-RADS classification is based on the ultrasound image characteristics of thyroid nodules, and does not involve the clinical data of patients or other ultrasound information. However, factors such as sex and age of patients, size and number of thyroid nodules and cervical lymph node abnormality or not affect the clinical treatment of thyroid nodules [7–9]. At present, the optimization of thyroid nodule classification is based on the subjective experience of sonogrphers, and there is no unified optimization standard. Therefore, we developed and internally validated a clinical prediction model for predicting C-TI-RADS classification optimization.
In this study, according to Logisitic regression analysis, C-TI-RADS classification level, cervical lymph node ultrasound abnormality and thyroid nodule size were the most important predictors of C-TI-RADS classification optimization, followed by sex, age and number of thyroid nodule. The established nomogram model for predicting C-TI-RADS classification optimization has an AUC of 0.790, a sensitivity of 70.8%, a specificity of 74.4% and an accuracy of 72.2%. The calibration curve and clinical decision curve also showed good consistency and net benefit, indicating that the prediction model has potential clinical application value.
A study of 5162 healthy individuals followed up for 5 years [10] showed that most nodules of level 4A and above had their classification adjustment during the follow-up, and the higher the classification level, the higher the risk of malignant progression. The results of this study showed that in C-TI-RADS classification, 4A/4B/4C had a higher probability of optimization (72.1%, 75.1% and 69.0%, respectively), and the OR value of 4B was 33.1, which was consistent with the clinical consensus that 4B was used as the cut-off point for benign and malignant diagnosis of thyroid nodules[3]. Besides, 85.3% of the patients with abnormal cervical lymph node ultrasonography underwent C-TI-RADS classification optimization. In multivariate regression analysis, the adjusted OR value of cervical lymph node ultrasound abnormalities was 5.0, which further confirmed that cervical lymph node ultrasound abnormality was an independent risk factor for effectively predicting the occurrence of C-TI-RADS classification optimization, and could be used as a supplementary diagnostic factor for thyroid nodules. In terms of thyroid nodule size, the prediction model showed that thyroid micronodules (less than 10mm) were more likely to have C-TI-RADS classification optimization than thyroid macronodules (the percentage of optimization was 61.2% and 50.9%, respectively). For non-minor nodules with high C-TI-RADS level (such as 4B), needle biopsy or surgery is the best treatment. However, most of the thyroid micronodules with higher classification level almost are small carcinomas with low malignant degree [11] and they often growth slowly. Sonographers tend to reduce their classification in actual diagnosis, so as to reduce unnecessary needle biopsy or surgery of thyroid micronodules and avoid overtreatment. In addition, in terms of patient age, the prediction model showed that young men had a higher probability of C-TI-RADS classification optimization than older women. Many studies have also proposed that young male patients with thyroid cancer are more malignant, aggressive and have a greater risk of recurrence [12, 13].
Compared with other TI-RADS classification optimization models, this study included clinical risk factors that considered in the actual diagnosis, which was in line with the clinical diagnosis model of thyroid nodule. At present, most prediction studies [14–16] establish prediction models based on ultrasonic characteristics of thyroid nodules, including location, size, composition, echo, shape, margin, calcification, blood flow signal, halo sign, etc. Although the ultrasound features included in various studies are different, overall, the optimized TI-RADS classification can maintain high sensitivity and diagnostic accuracy, and avoid some unnecessary biopsies or surgeries [17]. Ling Chen .et al [18] included nodular halo sign and age as risk factors in their prediction model, and obtained high sensitivity (88.4%) and specificity (91.7%).In addition, some predictive models also take such as ultrasound elastography, enhanced ultrasound, genetic testing and laboratory indicators into account[19–22], which are more accurate and sensitive than single TI-RADS classification. However, whether the improvement of its diagnostic value is greater than the improvement of cost of the medical treatment still needs in-depth clinical research to verify. While, the prediction model in this study not only improves the diagnostic efficiency of benign and malignant thyroid nodules (AUC = 0.969), but also does not involve other imaging or biochemical examination techniques, which is in line with the principles of health economics and has direct clinical application value.
This study has the following limitations: ① Inter-observer variability and the subjectivity of recognition images may affect the validity of the model. ② This study is a single center retrospective study, and there may be some selection bias. ③ This study discussed the risk of C-TI-RADS classification optimization, but did not discuss whether the result of optimization increased or decreased. ④ other potential clinical risk factors were not included in this study, such as body mass index, living environment, medical environment, location of thyroid nodules, and radiation exposure history of patients [23–25]. In the future, large sample studies are still needed to further verify the validity and extrapolation of this model, and to explore multi-center and prospective prediction models with higher diagnostic efficiency.