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Thursday, April 01, 2004In the latest research, Danesh and his colleagues used data from an Iceland study of heart disease that began in 1967. They compared 2,459 people who had a heart attack or died of heart disease over 20 years of follow-up with 3,969 participants who did not have a heart attack. Frozen blood samples were tested for CRP levels. The researchers calculated that those with higher levels of CRP had a 45 percent increased risk of heart disease compared with those with the lowest levels. The researchers also analyzed 22 studies on the topic and found that patients with higher CRP levels had a 50 percent higher risk of heart disease. That is far less than the early studies indicated. Eleven of the 22 studies analyzed were done before 2000, and together they showed a 100 percent increase in risk, or a doubling of the danger, the researchers said. "It's a cautionary tale about how high the bar really needs to be before we roll out scientific advances into the community and into the clinic," Danesh said. That's a fair criticism. Tests that are touted as predictors of future disease really should be held to a high standard. If 33% of people who never get disease have high CRP levels compared to 44% of people who end up with disease, then its predictive value is rather limited. (The study's abstract is here.) The authors of the study aren't shy about pointing this out: 'There's no good scientific reason to be using it as a predictive test,' said Dr. John Danesh, one of the British researchers at the University of Cambridge. And this: Danesh and his colleagues said groups that recommend the test should rethink their advice. Which has Dr. Paul Ridker, the biggest CRP proponent in the country, and not coincidentally holder of a patent for a high-sensitivity CRP test, riled: The authors "have the nerve to say it's not comparable to other risk factors, but it's exactly the same as blood pressure," says Paul Ridker of Boston's Brigham and Women's Hospital and a pioneer of CRP testing. The nerve of them! To challenge the media's favorite Harvard cardiologist. Judging from the CNN article, there was quite a bit of pressure at the American Heart Association/CDC panel to adopt CRP more enthusiastically: Dr. Thomas Pearson of the University of Rochester said the panel noted the weakness of the evidence and urged further study when it drew up the guidelines. He said the panel members were criticized as "way too conservative, stodgy and sticks-in-the-mud" by those who wanted more widespread testing. "I think this is validating our conservatism," he said. Yes, it does. And good on them for ignoring the name calling and sticking to reason in adopting their guidelines. UPDATE: A reader comments: Each year I accumulate a list of questions to take to my next annual physical. This year's exam was two weeks ago, and the value of CRP testing was on my list. (Interestingly, when I went to the Quest Diagnostics office for a blood draw a week ahead, there was a poster on the wall of the examining room that was basically an advertisement for CRP testing. I now wonder if Dr. Paul Ridker might somehow have had an involvement. In response to my question, I learned they are doing quite a few more of them these days.) I went into the exam understanding that CRP is an enzyme produced in the liver in response to inflammation just about anywhere in the body, and that there was some association with inflammation in coronary arteries. I wondered how the test result would in fact be actionable. I was not surprised to hear my physician say the evidence didn't yet seem to show a sufficiently high predictive value for the test relative to coronary artery disease for it to be used routinely for that purpose--that if an elevated result came back in my case, it would not be very useful to him in terms of further tests or altering the existing medication regimen. This latest study seems to lend weight to that view. posted by Sydney on 4/01/2004 09:01:00 AM 0 comments 0 Comments: |
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