We Overestimate CAD Pretest Probability

The ACC/AHA clinical practice guidelines have a set of reference values for the pretest probability of >50% stenotic coronary artery disease based on the type of pain and age.  These values range from 2% in a 30 year old woman with non-anginal pain to 94% in a 60 year old man with typical angina.

And, turns out, this is way off.

This is a CTCA registry study of patients undergoing coronary angiography, 14,048 consecutive patients with suspected CAD, looking at both the incidence of 50% luminal narrowing (clinically interesting) and the incidence of 70% luminal narrowing (potentially flow-limiting), and correlating it to asymptomatic, non-anginal, atypical angina, typical angina, or “dyspnea only”.

The meaningful tables of results somewhat defy summarization, but, they have plenty of hypertensives with dyslipidemia – but not very many diabetics or smokers – in their cohort.  In the end, however, none of the observed CAD was anywhere close to the predicted pretest probabilities.  The cohort with the highest prevalence of CAD was the typical angina in age 70+ males – but even that led to only 53% having a 50% lesion.  More than anything, age and gender the most significant predictors of CAD – with no population of women having greater than 29% incidence.

It’s an interesting table worth looking at – CAD really doesn’t kick in until after age 40, and, even then, only mostly in men, and, even then, only in patients with typical symptoms.  Once you hit age 50 in men, however, there’s CAD everywhere, even with atypical (or no) symptoms.

There was also some variability by study site – with the 2,225 from Korea having very little CAD and the 29 from the Swiss site having markedly more, but the remainder are relatively similar.

I love studies that just present reams of data and don’t try to push any particular sponsored agenda.

“Performance of the Traditional Age, Sex, and Angina Typicality–Based Approach for Estimating Pretest Probability of Angiographically Significant Coronary Artery Disease in Patients Undergoing Coronary Computed Tomographic Angiography”
http://www.ncbi.nlm.nih.gov/pubmed/22025600