Views vary about how to avoid nephrogenic systemic fibrosis (NSF). In Europe, it is contraindicated to use gadodiamide, gadopentetate dimeglumine, and gadovertisamide in patients who have a glomerular filtration rate (GFR) of less than 30 mL/min, and these agents may only be used with caution in patients who have a GFR between 30 and 60 mL/min. Similar restrictions have not been introduced for the other six gadolinium-based contrast agents available in the European market. In the United States, the US Food and Drug Administration introduced a class ban and warned about the use of gadolinium-based contrast agents in patients who have reduced renal function. However, European and American guidelines about how to avoid NSF are generally not very different.