Tal achado vem de encontro com o grande número de testes ergométricos realizados em pacientes de risco intermediário mas que são na verdade de baixo risco, aumentando o número de falsos positivos (prevalência baixa de doença) e levando a um grande número de cateterismos "brancos"!
Los Angeles, CA - The methods commonly used to estimate the pretest likelihood of coronary disease in patients referred for computed-tomography angiography (CTA) greatly overestimate the actual prevalence of coronary disease, especially in women, new data from the CONFIRM registry show [1].
The study was published online October 24, 2011 in Circulation.
CONFIRM senior investigator Dr James Min (Cedars-Sinai Medical Center, Los Angeles, CA) told heartwire, "We found that our ability to accurately estimate the pretest likelihood was pretty poor, on average, and whatever pretest likelihood estimate we came up with was usually about three times higher than the actual observed prevalence of disease."
"We've put this out as a wake-up call that maybe a lot of these people don't need testing," Min said. "Maybe we're just severely overestimating the likelihood of disease, and in fact we're just wrong on our pretest estimates."
Min explained that the most common methods for estimating a patient's chances of having coronary disease, such as the Diamond-Forrester risk score or the Coronary Artery Surgery Study (CASS) criteria, are based on age, gender, and the patient's angina symptoms. These systems were created several decades ago, before statins, at a time when smoking was much more prevalent. These methods were developed for patients referred for invasive coronary angiography but are still being applied to patients referred for noninvasive CT imaging, Min said. "We thought that it was maybe a different population and, for a whole host of reasons, we felt a contemporary revision was needed."
The CONFIRM researchers, led by Dr Victor Cheng (Cedars-Sinai Medical Center, Los Angeles, CA), identified 14 048 consecutive patients with suspected CAD who underwent coronary CTA. The patients' pretest likelihoods of CAD were estimated based on the table of probabilities in 2003 American College of Cardiology/American Heart Associationclinical practice guidelines for management of patients with stable angina. The likelihood of each patient having at least a 50%-diameter coronary stenosis (CAD50) and the chances they had at least a 70%-diameter stenosis (CAD70) were calculated separately and then compared with the findings from CTA images. In the study, typical angina was associated with CAD50 in 40% of men and 19% of women and CAD70 in 27% of men and 11% of women and was a better predictor of the appearance of disease in the CT images than any of the other symptom categories (p<0.001 for all comparisons).
Importantly, the CAD50 and CAD70 prevalence observed in the CTA images was substantially lower than the prevalence predicted with traditional estimate methods. In the overall population, the estimate of CAD50 prevalence calculated with the conventional method was 51%, but the prevalence of CAD50 as seen in the images was only 18%. For CAD70, the estimated prevalence was 42%, but the prevalence seen in the CT images was only 10% (p<0.001).
The marked overestimation of disease prevalence by the standard probability methods was found at all participating centers and across all sex and age subgroups. Min pointed out that the prevalence of coronary disease is more severely overestimated in women. For women, the estimate prevalence of CAD50 and prevalence shown by CTA was 41% vs 13%. For CAD70, the estimate was 26%, but the observed prevalence in the images was only 6%. "We were just really off on our estimates of the likelihood of disease in women," Min said.
A new blueprint for estimating CAD risk
The results of the study "suggest that successfully updating pretest probability estimates of CAD in populations similar to CONFIRM may identify a large percentage of low- or intermediate-likelihood patients in whom additional testing may not be warranted," Cheng et al explain.
"This might serve as a blueprint for people who are considering testing for noninvasive imaging. . . . They can look at these tables and say, 'I thought it was 45%, but it's really 15%, so maybe I'll consider not testing this individual,' " Min said. His group expects to soon produce a list of "parsimonious questions" that physicians can ask of their patients to quickly and accurately estimate their risk of CAD.
Min pointed out that so far all of the pretest likelihood methods provide estimates of coronary disease, not estimates of the likelihood of coronary events. So the next step for the CONFIRM researchers will be to develop global scoring systems to estimate both the risk of coronary disease and the risk of coronary events, he explained.
| This study was supported by the National Heart, Lung, and Blood Institute. |
Nenhum comentário:
Postar um comentário