Contradictory study results fuel controversy over contrast danger

We've been watching the wrangling over contrast-induced nephropathy for several years now. Visipaque scored a big win in 2003 with a study in The New England Journal of Medicine finding that the iso-osmolar agent was significantly safer than a low-osmolar agent (Omnipaque) in preventing contrast-induced nephropathy in coronary angiography patients. Last year, the debate took on added intensity with a slew of new studies suggesting that the NEJM study may not be the final word on the subject; others weighed in with new information holding that the more costly iso-osmolar agent was not necessarily that much better than low-osmolar agents.

The issue is hugely important. CT use and the need for contrast are soaring. At the same time, the populations most susceptible to contrast-induced nephropathy, such as those with diabetes and the elderly, are growing dramatically. Meanwhile, medical facilities are under tremendous pressure to improve quality by, for example, reducing the incidence of CIN and also to control costs.

Our review, which appears on page 32, didn't reach definitive answers about how to resolve these rival demands. There are simply too many competing voices, studies, and ideas for any true consensus to form on the topic of how best to limit CIN or even how important it is to do so.

But we did learn a lot about the issues and what is not known. All factors suggest that the radiology community needs to pay a lot more attention to how it uses and manages x-ray and CT contrast. A few key points emerged:

• More randomized trials are needed to examine the relative impact of low- and iso-osmolar agents in standard CT and x-ray exams. Our review found seven randomized studies comparing iso- and low-osmolar agents in populations at risk for contrast nephropathy. Only one of those studies covered CT. The rest involved coronary angiography. Even then, the results for both types of agents were mixed.

• Radiologists need to be more critical of the sources and methods used in some of the clinical trials. Many of the clinical trials available today have been backed by particular companies with particular agents in the market. Methodologies have been mixed. Variations among different types of low-osmolar agents have been obscured. Many trials focus on only high-risk patients where it is easier to show differences between agents.

• Radiologists need to be more cautious about interpreting results. Many of the physicians representing particular points of view have ties to the different contrast vendors.

• Finally, all facilities that use contrast should take a close look at their protocols for managing contrast use and reducing the chance of CIN. Those familiar with the topic say these contrast protocols vary widely.

One definition of quality in healthcare is consistency in the way a particular type of care is provided. To the extent that contrast protocols differ from one facility to the next, it suggests a lack of consensus and true understanding about what works and at what cost.

At the very least, facilities should get out these protocols and give them a new look in the light of emerging information and data. There are a host of questions to ask in these reviews: Is contrast really needed, and if so, can the amount be reduced? How are patients screened for susceptibility to CIN? Are hydration procedures in place? Do serum creatinine levels need to be tested after the scan?

As one source noted in our article, contrast-induced nephropathy is a moving target. While more evidence is needed, more is emerging every day. Alert radiologists and hospital administrators need to take steps to assure that their decisions are based on the latest as well as the best information.

What are your thoughts on this topic? Please e-mail me at jhayes@cmp.com.