Beware the "false positive" stress test

There's a widely-known (among cardiologists) problem with nuclear stress tests. It's called the "false positive." (Nuclear stress tests are known as stress Cardiolites, stress thalliums, stress Myoviews, persantine stress tests, adenosine stress tests)

Stress tests, nuclear and otherwise, are helpful for identifying areas of poor blood flow. If an area of poor blood flow is detected and the area is substantial, then there may be greater risk of heart attack and other undesirable events in the relatively near future.

What "false positive" means is a stress test that shows an abnormality but it's not true--it is falsely abnormal. There are a number of reasons why this can happen. The problem is that this phenomenon is very common. Up to 20% of nuclear stress tests are false positives.

There are indeed situations where there may an abnormality and it is not clear whether it is true or false. This may lead to a justifiable heart catheterization or CT coronary angiogram. But, given the extraordinary number of false positives, there's a lot of gray in interpreting these tests. Hospital staff, in fact, call nuclear medicine "unclear" medicine. It's common knowledge that you can often see just about anything you want to see on a nuclear image of the heart. Abnormalities in the bottom of the heart, the "inferior" wall, are especially common due to the overlap of the diaphragm with the heart muscle, yielding the appearance of reduced blood flow. Defects in the front of the heart heart are common in females with large breasts for the same reasons.

The problem: The uncertainty inherent in nuclear stress tests opens the door to the unscrupulous or lazy practitioner. Any blip, tick, or imperfection on the nuclear images serve as carte blanche to drag you into the hospital for procedures.

This abusive practice is, in my experience, shockingly common for two reasons: 1) It pays better to do heart catheterizations, and 2) Defensive medicine.

What's the disincentive? Only doing the right thing and maintaining a clear conscience. Slim reasons for many of my colleagues--and a lot less money.

If you are without symptoms and feel fine, and a nuclear stress test is advised by your doctor, followed by a discussion of an abnormality, insist on a discussion of exactly what is abnormal, just how abnormal, and what the alternatives might be. If you receive unsatisfactory or incomplete answers despite your best effort, it's time for another opinion.

Comments (11) -

  • Michelle C

    10/25/2007 4:23:00 PM |

    I was very interested to see this article.  My father had a cardiolyte test.  The results said that his arteries were clear, but that he'd had a heart attack in the anterior infraseptal wall.  He was shocked because he's never had any symptoms.  His doctor wanted to refer him for a possible angiogram, but my dad declined.  Now I wonder if this was a misdiagnosis.  It's made getting health insurance next to impossible for him, and he regrets the day he ever agreed to the test in the first place.

  • Jerry Lewis

    10/16/2008 12:04:00 PM |

    Stress management is a very important factor to improve short term memory loss. Stress causes the body to release a hormone called cortisole which blocks the memories from being registered. Since it is a known fact that all women going through early menopause have stress, it is essential to stay positive and stay stress free.

  • Anonymous

    7/24/2009 1:02:26 AM |

    What is the incidence of false positive nuclear stress test results in women who have had previous (non-cosmetic) breast surgery for cancer and benign lesions?  I would appreciate reference to studies if any.

  • R.G.

    9/2/2009 8:40:08 PM |

    I am so glad to find this site.  I recently had the Thallium test which came back positive, yet I'm not overweight, don't smoke, have normal to low blood pressure and a resting heart rate of 60.  My risk factors are being post-Menopausal and having a family history.  I asked my MD if he would be willing to re-test and he refused, so I'm going to a different doctor, not telling him anything about my previous results and get a second, unbiased opinion.  Then if that one comes back positive, I'll know for sure what steps to take next.

  • Michelle

    10/30/2009 8:28:16 PM |

    I had an abnormal stress test and just had an angiogram today. It showed no blockages and that I have large arteries. My cardiologist says my heart is an great shape. It does put my mind at ease knowing I don't have CAD. Since my mom had her first 95% blockage at 36.


  • Anonymous

    11/9/2009 11:16:14 PM |

    I had a false positive stress test.  The stress test came out markedly positive, which prompted my doctor to send me to heart catheterization immediately the next day.  But the heard cath showed that my heart was completely fine.  Of course, you can imagine the stress that I went through.  Even though it is good to know that my heart is fine, I am feeling like short of breath once in a while, probably  due to lack of enough exercise as well as possible anxiety.  I wish that noone had to go through this.

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  • Anonymous

    4/18/2011 11:29:39 PM |

    I had a false positive Nuc Stress Test last week. After research the reason was due to the following. 18 months ago I had bariatric surgery The Ruin Y, procedure and lost over 100 pounds. My BMI went from 45 to 25. Last week after eating a Beef Stick I developed chest pains radiating down my left arm and was taken to ER Via ambulance. After the stress test, I had a Cath and was found to be normal - 20% blockage in one artery. My Bariatric Surgeon said I suffered from "Dumping" which can mimic an heart attack. The abnormal Nuc Stress test was due to a overlay of tissue on the posterior part of heart from the surgery. Next time I talk with Surgeon before more tests, but they were two different cities and being 55, with a blood AIC over 10 for 10 years, was prime candidate for MI. Better safe than sorry!

  • Charlie

    12/11/2012 1:45:22 PM |

    I am a Nuclear Medicine technologist.  Several factors influence a false positive test:

    1. Motion - heavy breathing or sliding from the original position in the scan can cause a false positive.  This is generally checked by the tech after the scan is finished.  In many cases the scan will be performed again if there is over a certain amount of movement visualized in a graph.

    2. Breast size - patients with large / dense breasts or with breast implants (saline or otherwise) will definitely cause a breast attenuation artifact that looks similar to an infarction or ischemia.  The resting images typically provide a map of the heart tissue to view what possible attenuation might occur, or previous infarctions.  Generally cardiologists are able to determine the factor based on information given from the technologist, as well as location of the defect in the image.

    3. Diaphragm - the diaphragm on some patients can be very dense (patients with a large belly pushing the diaphragm up, or a thin person having an elevated hemidiaphragm that sits too closely to the cardiac emmissions.  This can cause an inferior wall defect.

    4. Coronary abnormalities - certain twists and turns can cause a much higher reduction of blood flow at the time of the test.  Not common, but I've seen it in correlation to a angiogram.  Also if you have several vessels that are equally diseased, the global perfusion will be equal and hard to discern of a specific disruption of blood flow to a particular area.

    5. Cardiologist / Radiologist reading - some cardiologists and radiologist read much different than others.  I've seen some tests that have a tiny defect, most likelly from motion or obesity that is read positive automatically without any further detail.

    My advice is this.  I think it is a great test in conjunction with a full work up by a cardiologist you trust.   If it comes back positive, know that it's possible you are fine and need further workup.  90-95% of the tests I perform are negative, with very very rare false negatives (meaning if it's negative, it's very likely you do not have trouble with perfusion to your heart).  Most of my false positive performances come from patients that have a large BMI, large breasts, breath heavily, or cannot raise both arms.

    Keep in mind an angiogram is up to interpretation as well.  Many cardiologists treat different blockages in different areas much differently.  Some treat with medicine and others will stent areas that are borderline treatable.  

    Hope this helped a bit.  Not much in medicine is completely black and white, these tests are tools to help give the best treatments possible and they are becoming better and better everyday.

  • Jolene

    8/9/2013 9:36:49 PM |

    I have a BMI of 66! I am 368 ibs. I had a nuclear stress test done. the activity portion failed with a lower part being gray or "no flow" on the images. I DID move my legs at teh end of the test without thinking. However when i asked for a new test the family nurse Practitioner (who told me the results) refused saying it wouldnt change the facts? What facts!? I am 31, overweight. Thats it. I have NEVER smoked, done drugs, drank, my Cholesterol is a 98, my BP is usually borderline (147/74)  or low (112/72). I have no family history of anything, no one has died from heart disease or had heart disease? So again, what facts? Also she as i said is a FNP! Not the Cardiologist? So why is she even looking at my charts and giving me any kind of advice about procedures or anything? Any help understanding this would be much appreciated. Thanks.


    7/8/2014 2:43:36 AM |

    I have stress test positive in 2006 followed by Angiogram negative. Since then around 6 stress tests positive (equivocal). I am diagnosed for Rosucar ASP 10(Rosuvastatin and Asprin capsules) & Telmisartan 40 mg and amlodipine  5mg.

    I don't have any complaints but for hypo thyroid TSH 7.80.

    Now cardiologist advise to go for stress test again but this time stress test thallium. Will it identify correctly?

    What are the ill facts and side effects about Stress test Thallium

    Please advice me.