“Too many false positives”

“Do you really think I need a heart scan?” asked Terry.

“My doctor said that heart scans show too many false positives. He says that many people end up getting unnecessary heart catheterizations because of them.”

At age 56, Terry was becoming increasingly frightened. His father had suffered his first heart attack at age 53, Terry’s paternal uncle had a heart attack at age 56, his paternal grandfather a heart attack at age 50.

Is this true? Do heart scans yield too many false positives, meaning abnormal results when there really is no abnormality?

No, it is not. What Terry’s doctor is referring to is the fact that, in the decades-long process that leads to heart attack, heart scans have the ability to detect early phases of developing coronary atherosclerotic plaque.

Let’s take Terry’s case, for example. Given his family history, it is quite likely that he does indeed have coronary atherosclerotic plaque. Will it be detectable by performing a stress test? Probably not. In fact, Terry jogs and feels well while doing so. While a stress test abnormality that fails to reach conscious perception is possible, it’s fairly unlikely given his exercise routine.

Will Terry’s coronary atherosclerotic plaque be detectable by heart catheterization? Very likely. But why perform an invasive hospital procedure just as a screening test? Should a woman wishing to undergo a screening test for breast cancer undergo breast removal? Of course not.

Is waiting for symptoms a rational way to approach diagnosis of heart disease? Well, when symptoms appear, it means that coronary blood flow is reduced. Stents and bypass surgery may be indicated. The risk of heart attack and death skyrocket. Sudden death becomes a real possibility.

In the 30 or so years required to establish sufficient coronary plaque to permit the appearance of symptoms or the development of an abnormality detectable by stress testing, there were many years when the disease was early--too early to generate symptoms, too early to be detectable by stress testing.

That’s when heart scans uncover evidence for silent coronary atherosclerotic plaque.

Should we call this a “false positive” just because it doesn’t also correlate with “need” for a catheterization, stent, bypass operation or result in heart attack within the next few weeks?

The detection of early plaque is just that: early disease detection.

Imagine, for instance, that the breast cancer that will grow into a palpable nodule or mass detectable by mammogram is detectable by a special breast scan 15 years before it becomes a full-blown tumor, metastasizing to other organs. What if effective means to halt that earliest evidence of cancer could put a stop to this devastating disease decades ahead of danger? Is this a “false positive” too?

In my view, this is the knuckleheaded thinking of the conventional practitioner: “Don’t bother me until you’re really sick.” Prevention is a practice that has become fashionable only because of the push of the drug industry. Nutrition is an afterthought, a message conceived through consensus of “experts” with suspect motivations and allegiances.

So, no, heart scans do not uncover “false positives.” They uncover early disease--true positives--years before it is detectable by standard tests or by the appearance of catastrophe. But that is the whole point: Early detection means getting a head start on prevention.

Do heart scans lead to unnecessary heart catheterizations? Yes, sadly they do. But not because heart scans are false positive. It happens because of unscrupulous or ignorant cardiologists who use the information wrongly. In my view, heart scans should NEVER lead directly to heart catheterization in an asymptomatic patient. Heart scans, as helpful as they are, do not modify the standard reasons for performing heart procedures.

If a car mechanic is dishonest and fixes a carburetor that didn't need fixing, should we condemn all car mechanics? No, of course not. We only need to develop the means to weed out the bad apples. The same applies to heart scans.

Comments (6) -

  • steve

    9/4/2008 2:43:00 PM |

    why even bother with expense of a heart scan and radiation exposure when detailed Lipoprotein analysis may be all you need?  If you have many small LDL particles isn't that enough to say you probably have CAD and should address it; while if your LDL particles are mostly large your probably ok

  • Anonymous

    9/4/2008 5:41:00 PM |

    Small LDLs alone may or may not mean one has plaque. Likewise, someone that doesn't have too many small LDLs might have plaque.

    Plus, like Dr. Davis likes to point out, the most important heart scan is not the 1st heart scan but the 2nd heart scan. You see, if someone has any plaque (above zero), then after they take the necessary steps to try and slow down, stop and even reverse the plaque they have NO WAY to know if the steps they took are enough whithout the results from the 2nd scan (which is usually taken 1 year after the lipoproteins have been corrected).

    The amount of radiation is about the same as several chest x-rays:


  • MedPathGroup

    9/5/2008 7:48:00 AM |

    Hi there. I am just dropping by. I came across this blog when i was researching about coronary bypass surgery. Very informative stuffs I can add in to my research. Thanks for sharing this information. I will keep on visiting this blog for more interesting posts.

  • joel oosterlinck M.D.

    9/5/2008 8:30:00 AM |

    firs of all this blog is really interesting I am a french family practitioner with specialisation in hyperbaric and gynoaecology.
    My question is heartscan is not a mainstream test in my area  where 64 slices scan machines arrived 2 years ago some of my cardiologists advised for 64 slice angiogram for screening . I read in european literature that there is an unresolved problem with  false negatives  in heart scan can you please elaborate with this false negative issue ?

  • Tony Romeyn

    12/2/2008 5:08:00 AM |

    My story, sorry it is a bit long.
    For many years I have been dealing with medium to high cholesterol levels. High cholesterol is only one part to the danger of plaque buildup in the arteries and an eventual possible heart attack. Other risk factors such as, Smoking, Hypertension, Diabetes, Obesity, Inactivity, Stress and Family history all play a role in High Cholesterol.

    It was approximately 10-15 years ago that my Doctor suggested that I go on medication with one of the Statin drugs and Lipitor is what he suggested for me. With a great amount of reluctance I finally agreed, but I certainly was not happy with the potential side effects, as there are many. The worst side effect that could happen was a muscle tissue breakdown with severe muscle pain. Well low and behold within 10 days I have severe muscle tissue pain and took my Lipitor pills and dumped them down the toilet. When I told my Doctor what I had done he was not too happy but he could identify with what was happening.

    It was at that point that I started to ask that although my blood test showed that I had high cholesterol, did that necessarily indicate that I had clogged arteries. I continued to ask the same question over many years. My family Doctor continued to advise me that he would like to try another statin med called Zocor. Again I reluctantly agreed and started to research how others did with Zocor on the Internet. Again many reported of similar side effects as I experienced with Lipitor.

    That year during vacation time I picked up a newspaper……..I am a news junky……. and there was an article that hit me like a ton of bricks; Bacol by Bayer was being recalled due to a number of reported deaths and other severe side effects. At that point I took my Zocor meds and dumped them down the toilet also………….oops I probably polluted the drainage water………. determined never to do a Statin drug again.

    Years went by and tests were done from time to time, sometime showing medium to higher levels.

    Then came late February of this year 2008. Within three days of having a few dizzy spells I collapsed and had emergency surgery due to an ulcer which had perforated an artery. That is a whole story in itself, but just one note if you are taking a good number of Aspirin and Ibuprofen, you may, no you must check with your Doctor to see what is happening with your stomach.

    In that short period of time just before my surgery I had lost about 6 units of blood. During my healing process I was told I was lucky to be alive. A few weeks into the recuperation time I can to reflect on the fact that my heart must have to have been awfully strong to have dealt with significant blood loss. Then I began to re ask the same question, hey my arteries could not be blocked, otherwise my heart would never have kept up. I posed this question to my surgeon, and he confirmed that that is not necessarily true.

    Now we come to the time of a recent cholesterol test which showed numbers higher than ever before. The same answer you need to go on Cholesterol lowering drugs. I came to the point and said to my Doctor I want to get a test to see if my arteries have buildup and how do we do this. Without significant physical symptoms our medial system does not allow for such a test, which is either an Angiogram or a CT Scan.

    In recent years a new 64-Slice CT scanner became available, a non-invasive evaluation of arteries. But our medical system still does not allow  a scan to be done without significant physical symptoms.
    Now here comes into play the private diagnostic clinics. In consultation with my Doctor I looked into and booked to get a Heart Scan (Coronary Artery Calcium Scoring) done at the Canada Diagnostic Clinic in Vancouver. An appointment was available almost immediately and of course I would have to pay for this myself at a cost of $690.00, plus travel to Vancouver and an overnight stay. Quite costly and not affordable to everyone. (Please scroll down for details of the scan)
    NOW THE GOOD NEWS! My heart arteries only showed a very minor calcium build up at two points. My Calcium score was 19.

    NO NEED TO GO ON RISKY STATIN DRUGS, SUCH AS Lipitor, Zocor, Baycol or a more recent addition Crestor (here is what is mentioned on the Johns Hopkins Hospital website - "although the potency of Crestor appears to be fully established, its safety is not. Unless there is an overwhelming reason to take a very new drug, the best approach is to wait for some time to pass to allow unforeseen problems, if any, to be detected." WITH POSSIBILTY OF SIGNIFICANT SIDE EFFECTS

  • buy jeans

    11/3/2010 2:24:56 PM |

    In my view, this is the knuckleheaded thinking of the conventional practitioner: “Don’t bother me until you’re really sick.” Prevention is a practice that has become fashionable only because of the push of the drug industry. Nutrition is an afterthought, a message conceived through consensus of “experts” with suspect motivations and allegiances.