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31-10-2011 | Cardiology | Article

Guideline probabilities may be ‘greatly overestimating’ CAD prevalence

Abstract

Free abstract

MedWire News: New data from the CONFIRM registry show that invasive angiography-based guideline probabilities greatly overestimate the actual prevalence of coronary artery disease (CAD).

These findings suggest that if pretest probability estimates of CAD are updated, clinicians will be able to identify a large proportion of low- or intermediate-likelihood patients in whom additional testing may not be needed, report Victor Cheng (Cedars-Sinai Medical Center, Los Angeles, California, USA) and colleagues.

The American College of Cardiology and American Heart Association have recognized age, gender, and angina typicality as the pretest predictors of angiographically significant CAD (≥50% diameter stenotic CAD), they explain. The resultant reference probabilities have been adopted for use in guidelines for the management of angina and coronary computed tomographic angiography (CTA). However, the reliability of guideline probabilities has not been investigated in patients referred for noninvasive CAD testing.

Cheng and team therefore identified 14,048 consecutive patients from CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter Registry) with suspected CAD who underwent CTA. The researchers recorded angina typicality using accepted criteria, and determined the pretest likelihoods of CAD with a diameter stenosis of 50% or more (CAD50) and 70% or more (CAD70), using guideline probabilities. CTA images were evaluated by more than one reader to assess the presence of CAD50 and CAD70.

The findings revealed that typical angina was significantly associated with CAD50 in 40% of men and 19% of women, and CAD70 in 27% of men and 11% of women (p<0.001). It was also a stronger predictor of the appearance of disease in the CTA images than any of the other symptom categories (p<0.001), which included dyspnea and nonanginal chest pain.

The observed prevalences of CAD50 and CAD70 were substantially lower than those predicted by guideline probabilities in the overall population (18 vs 51% for CAD50, 10 vs 42% for CAD70; p<0.001). This was driven by pronounced differences in observed and predicted rates in patients with atypical and typical angina, the researchers explain.

Marked overestimation of disease prevalence by guideline probabilities was found at all participating centers and across all age and gender subgroups, they note.

Cheng et al believe that one of the explanations for the extent of overestimation by guidelines probabilities may be the increased awareness of the potential hazards of CAD, which "may be prompting lower-risk symptomatic patients to seek earlier diagnostic evaluation".

They conclude in the journal Circulation: "Results from this study illustrate a major limitation in the practice of applying disease prevalence derived from invasive coronary angiography to populations undergoing initial noninvasive evaluation for CAD and highlights the need for updating probabilities of angiographically significant CAD in such populations."

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By Piriya Mahendra

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