Diagnostic accuracy of ultrasound, computed tomography, and magnetic resonance imaging for the evaluation of thyroid nodules

OBJECTIVES: This is a protocol for a Cochrane review (diagnostic). The objectives are as follows: To assess the diagnostic accuracy of US, CT, and MRI - each considered separately - in identifying malignant thyroid nodules, using histopathological examination as the reference standard. Each modality will be evaluated within its established role in the preoperative diagnostic pathway. This includes estimating the sensitivity and specificity of each imaging modality for differentiating malignant from benign thyroid nodules (the ability to correctly identify cancerous and non-cancerous nodules). A clearer understanding of each modality's accuracy is intended to support patient and clinician decisions - for example, whether further imaging is warranted when ultrasound is inconclusive, and whether surgery can be avoided in nodules reliably classified as benign. Secondary objectives Comparative accuracy: To compare the diagnostic performance of US, CT, and MRI for detecting thyroid malignancy, restricted to direct comparisons within studies that evaluated two or more of these tests in the same participants. Indirect comparisons across separate studies will not be performed for inference, as differing clinical roles, case-mix, and selection make them vulnerable to confounding by indication; any such observation will be reported descriptively and regarded as exploratory. Sources of heterogeneity: To investigate potential sources of variation (heterogeneity) in diagnostic accuracy. Specifically, we will examine whether factors such as nodule size, use of contrast media (for CT or MRI), variations in imaging protocols (e.g. ultrasound risk stratification systems, MRI sequence parameters), study design (prospective vs. retrospective), and patient characteristics (e.g. endemic goitre populations, baseline prevalence of malignancy) significantly affect sensitivity or specificity.