No One Knows How To Diagnose CAD

And, once they diagnose it – it doesn’t seem like anyone knows what to do with it, considering all the brouhaha these days about potentially unnecessary PCI and stenting.

But, this is a prospective coronary CT angiography registry that was reviewed to determine whether any value was added with the CCTA over conventional stress testing in patients without known CAD.  They reviewed 22,551 patient records, excluded patients with known CAD, incomplete data, and patients who hadn’t undergone a recent (<3 months) cardiac stress test, and ended up with 6,198 patients.

The point the authors seem to be trying to make is that CCTA is a better test than stress testing, but that’s only part of the story.  What they note that is interesting along the way is that there is absolutely no correlation between stress testing results and CCTA results.  Patients with normal, equivocal, and abnormal stress results had, essentially, the same incidence of normal, <50%, and >50% coronary stenosis.  And, the hidden story about how CCTA is being used in their patient cohort is fascinating – a younger group with typical chest pain and normal stress tests referred to CCTA vs. an older group with less typical symptoms and abnormal stress tests referred to CCTA.

But, then, finally they compare both of their disparate tests to the “gold standard” of invasive angiography, and they find that both tests are awful at predicting >50% coronary stenosis.  Stress testing was 60.4% sensitive and 34% specific, while CCTA was 94% sensitive and 37% specific.  So, we have two tests that are wrong about the presence of disease twice as often as they’re right – and these authors are using a clinically irrelevant 50% stenosis as their “gold standard”.

Rather entertaining to observe the difficulty the cardiology literature is having reconciling all their different imaging options with clinically relevant stenoses, much less outcomes.  Good thing all these inadequate tests are cheap and harmless….

“Coronary Computed Tomography Angiography After Stress Testing”

4 thoughts on “No One Knows How To Diagnose CAD”

  1. "Good thing all these inadequate tests are cheap and harmless…." Sometimes the only proper response to the lit is truculent sarcasm.

    50%, 70%, it's not really the main point to us, is it? We just want to know how safe they are to follow up with their PMD or cardiologist.

    I appreciate treadmill data, because (as I understand it), while it may be a poor test for diagnosing CAD, successful completion of the protocol predicts a very low rate of death, MI, etc. Must dig through the literature to find the supporting studies there…

  2. "Good thing all these inadequate tests are cheap and harmless…." Sometimes the only proper response to the lit is truculent sarcasm.

    50%, 70%, it's not really the main point to us, is it? We just want to know how safe they are to follow up with their PMD or cardiologist.

    I appreciate treadmill data, because (as I understand it), while it may be a poor test for diagnosing CAD, successful completion of the protocol predicts a very low rate of death, MI, etc. Must dig through the literature to find the supporting studies there…

  3. I've been trudging through David Newman's SMART EM podcast regarding stress tests; it's kind of a disjointed quagmire, but from what I've been able to synthesized from my intermittent listens, the stress test came out of risk-stratifying, essentially, STEMIs and NSTEMIs as inpatients to see which of them were appropriate for an invasive strategy or a non-invasive strategy. Some of the papers reviewed allude to what we think is important – stress tests to predict 30-day event-free survival in the low-risk population, but the earlier literature didn't think it was a very good test because of the high rate of false positives.

    I do tend to think the "standard of care" for low-risk chest pain right now is obviously moronic, but I haven't yet come up with a socially acceptable, teachable, safe, effective, alternative strategy, either for my patients capable of PMD follow-up, or my county population that is guaranteed not to have any follow-up.

  4. I've been trudging through David Newman's SMART EM podcast regarding stress tests; it's kind of a disjointed quagmire, but from what I've been able to synthesized from my intermittent listens, the stress test came out of risk-stratifying, essentially, STEMIs and NSTEMIs as inpatients to see which of them were appropriate for an invasive strategy or a non-invasive strategy. Some of the papers reviewed allude to what we think is important – stress tests to predict 30-day event-free survival in the low-risk population, but the earlier literature didn't think it was a very good test because of the high rate of false positives.

    I do tend to think the "standard of care" for low-risk chest pain right now is obviously moronic, but I haven't yet come up with a socially acceptable, teachable, safe, effective, alternative strategy, either for my patients capable of PMD follow-up, or my county population that is guaranteed not to have any follow-up.

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