Iodinated and gadolinium-based contrast media are used on a daily basis in most radiology practices. These agents often are essential to providing accurate diagnoses, and are nearly always safe and effective when administered correctly. However, reactions to contrast media do occur and can be life threatening. Therefore, it is critical for faculty and staff to know how reactions to contrast agents manifest and how to treat them promptly. The decline in renal function seen occasionally after intravenous administration of iodinated contrast agents is poorly understood and likely multifactorial, and its association with the contrast medium may be overemphasized. However, it is important that radiologists be aware of current understanding and strategies to decrease the incidence of renal dysfunction. Nephrogenic systemic fibrosis, a skin disease, is an adverse reaction related to use of some gadolinium-based contrast agents in patients with chronic renal failure. The types of gadolinium most often associated with this condition and the indications for withholding gadolinium are important and are discussed in this article. The use of enteric contrast agents and contrast agents during pregnancy and nursing are reviewed briefly. Current knowledge for safe use of contrast media and key concepts that all radiologists should know are summarized in this review.

IMPORTANCE Approximately 20% of thyroid nodules display indeterminate cytology. Molecular testing can refine the risk of malignancy and reduce the need for diagnostic hemithyroidectomy.OBJECTIVE To compare the diagnostic performance between an RNA test (Afirma genomic sequencing classifier) and DNA-RNA test (ThyroSeq v3 multigene genomic classifier). DESIGN, SETTING, AND PARTICIPANTSThis parallel randomized clinical trial of monthly block randomization included patients in the UCLA Health system who underwent thyroid biopsy from August 2017 to January 2020 with indeterminate cytology (Bethesda System for Reporting Thyroid Cytopathology category III or IV). INTERVENTIONS Molecular testing with the RNA test or DNA-RNA test. MAIN OUTCOMES AND MEASURES Diagnostic test performance of the RNA test compared with the DNA-RNA test. The secondary outcome was comparison of test performance with prior versions of the molecular tests. RESULTS Of 2368 patients, 397 were eligible for inclusion based on indeterminate cytology, and 346 (median [interquartile range] age, 55 [44-67] years; 266 [76.9%] women) were randomized to 1 of the 2 tests. In the total cohort assessed for eligibility, 3140 thyroid nodules were assessed, and 427 (13.6%) nodules were cytologically indeterminate. The prevalence of malignancy was 20% among indeterminate nodules. The benign call rate was 53% (95% CI, 47%-61%) for the RNA test and 61% (95% CI, 53%-68%) for the DNA-RNA test. The specificities of the RNA test and DNA-RNA test were 80% (95% CI, 72%-86%) and 85% (95% CI, 77%-91%), respectively (P = .33); the positive predictive values (PPV) of the RNA test and DNA-RNA test were 53% (95% CI, 40%-67%) and 63% (95% CI, 48%-77%), respectively (P = .33). The RNA test exhibited a higher PPV compared with the prior test version (Afirma gene expression classifier) (54% [95% CI, 40%-67%] vs 38% [95% CI, 27%-48%]; P = .01). The DNA-RNA test had no statistically significant difference in PPV compared with its prior version (ThyroSeq v2 next-generation sequencing) (63% [95% CI, 48%-77%] vs 58% [95% CI, 43%-73%]; P = .75). Diagnostic thyroidectomy was avoided in 87 (51%) patients tested with the RNA test and 83 (49%) patients tested with the DNA-RNA test. Surveillance ultrasonography was available for 90 nodules, of which 85 (94%) remained stable over a median of 12 months follow-up.CONCLUSIONS AND RELEVANCE Both the RNA test and DNA-RNA test displayed high specificity and allowed 49% of patients with indeterminate nodules to avoid diagnostic surgery. Although previous trials demonstrated that the prior version of the DNA-RNA test was more specific than the prior version of the RNA test, the current molecular test techniques have no statistically significant difference in performance.

ThyroSeq v2 had higher specificity than Afirma GEC and allowed more patients to avoid surgery. Long-term surveillance is necessary to assess the false-negative rate of these particular molecular tests. Further studies are required for comparison with other available molecular diagnostics and for newer tests as they are developed.

Objective Molecular testing can refine the diagnosis for the 20% of thyroid fine needle aspiration biopsies that have indeterminate cytology. We assessed the diagnostic accuracy of molecular testing based on ultrasound risk classification. Methods This retrospective cohort study analyzed all thyroid nodules with indeterminate cytology at an academic U.S. medical center (2012-2016). All indeterminate nodules underwent reflexive molecular testing with Afirma Gene Expression Classifier (GEC). Radiologists performed blinded reviews to categorize each nodule according to the American Thyroid Association (ATA) ultrasound classification and the American College of Radiology Thyroid Imaging, Reporting and Data System (ACR TI-RADS). GEC results and diagnostic performance were compared across ultrasound risk categories. Results Of 297 nodules, histopathology confirmed malignancy in 65 (22%). Nodules by ATA classification were 8% high suspicion, 44% intermediate, and 48% low/very low suspicion. A suspicious GEC result was more likely in ATA high suspicion nodules (81%) than in nodules of all other ATA categories (57%; P = 0.04). The positive predictive value (PPV) of GEC remained consistent across ultrasound categories (ATA high suspicion, 64% vs. all other ATA categories, 48%; P = 0.39). The ATA high suspicion category had higher specificity than a suspicious GEC result (93% vs 51%; P < 0.01). A suspicious GEC result did not increase specificity for the ATA high suspicion category. Conclusion The PPV of molecular testing remained consistent across ultrasound risk categories. However, a suspicious GEC result was very likely in ATA high suspicion nodules and did not improve specificity in this sonographic category.

Using established imaging criteria, up to 21.8% of presumed HCC nodules are inaccurately characterized and many small HCC nodules remain undiagnosed.