Elsevier

International Journal of Cardiology

Volume 222, 1 November 2016, Pages 346-351
International Journal of Cardiology

Pre-test probability of obstructive coronary stenosis in patients undergoing coronary CT angiography: Comparative performance of the modified diamond-Forrester algorithm versus methods incorporating cardiovascular risk factors

https://doi.org/10.1016/j.ijcard.2016.07.180Get rights and content

Abstract

Background

Current guidelines recommend the use of the Modified Diamond-Forrester (MDF) method to assess the pre-test likelihood of obstructive coronary artery disease (CAD). We aimed to compare the performance of the MDF method with two contemporary algorithms derived from multicenter trials that additionally incorporate cardiovascular risk factors: the calculator-based ‘CAD Consortium 2’ method, and the integer-based CONFIRM score.

Methods

We assessed 1069 consecutive patients without known CAD undergoing coronary CT angiography (CCTA) for stable chest pain. Obstructive CAD was defined as the presence of coronary stenosis 50% on 64-slice dual-source CT. The three methods were assessed for calibration, discrimination, net reclassification, and changes in proposed downstream testing based upon calculated pre-test likelihoods.

Results

The observed prevalence of obstructive CAD was 13.8% (n = 147). Overestimations of the likelihood of obstructive CAD were 140.1%, 9.8%, and 18.8%, respectively, for the MDF, CAD Consortium 2 and CONFIRM methods. The CAD Consortium 2 showed greater discriminative power than the MDF method, with a C-statistic of 0.73 vs. 0.70 (p < 0.001), while the CONFIRM score did not (C-statistic 0.71, p = 0.492).

Reclassification of pre-test likelihood using the ‘CAD Consortium 2’ or CONFIRM scores resulted in a net reclassification improvement of 0.19 and 0.18, respectively, which would change the diagnostic strategy in approximately half of the patients.

Conclusions

Newer risk factor-encompassing models allow for a more precise estimation of pre-test probabilities of obstructive CAD than the guideline-recommended MDF method. Adoption of these scores may improve disease prediction and change the diagnostic pathway in a significant proportion of patients.

Introduction

Estimating the pretest probability of disease is a key step in the evaluation of patients with suspected coronary artery disease (CAD) as this influences clinical decision-making regarding the need for testing, the choice of test, and the interpretation of test results. The current European guidelines on the management of stable CAD recommend a tabular method for estimating pre-test likelihood of obstructive coronary stenosis based exclusively on age, sex and typicality of symptoms. [1] The underlying model uses a modified Diamond-Forrester (MDF) approach, which was extended to include patients older than 70 years, and updated by revising the predictive value of its variables. [2] Despite good internal validation measures, the proposed model was derived entirely from patients referred for invasive coronary angiography (ICA) rather than for non-invasive imaging, for which it is more commonly employed. Further, the MDF method does not account for important cardiovascular risk factors such as diabetes, hypertension or cigarette smoking. To address these shortcomings, new scores that include these risk factors were recently developed from multicenter efforts. The ‘CAD Consortium 2’ was derived from a pooled analysis of 5677 patients undergoing coronary computed tomography angiography (CCTA) and/or ICA in 18 centers in Europe and the United States, [3] while the recent CONFIRM score was developed from a cohort of 9093 patients undergoing CCTA in 8 centers from 6 countries. [4] Importantly, the CAD Consortium 2 score is a calculator-based score, while the CONFIRM score is an integer-based score aimed for easy calculation in the clinical setting.

The aim of this study was to compare the diagnostic performance of these 2 scores against the MDF method in patients referred for non-invasive coronary angiography. The 3 methods were assessed for calibration, discrimination and net reclassification, as well as for their ability to influence clinical decision making for intended downstream testing.

Section snippets

Population

We performed a retrospective analysis on prospectively collected data from a cohort of consecutive patients undergoing CCTA for the evaluation of CAD at our hospital between June 2011 and May 2014. Criteria for referral to CCTA were left to the discretion of the referring physician. Fig. 1 shows patient selection. Age < 30 years, known CAD, suspected acute coronary syndrome, preoperative assessment, and known left ventricular systolic dysfunction were among the exclusion criteria. Asymptomatic

Results

The baseline characteristics of the 1069 symptomatic patients undergoing CCTA for suspected CAD are listed in Table 2. The observed prevalence of obstructive CAD on CCTA was 13.8% (n = 147). Patients with obstructive CAD were more often male, were significantly older and had a higher prevalence of typical angina symptoms and of all the traditional cardiovascular risk factors except for family history. They also had significantly higher CAC scores (median 177, IQR 60–370) than those without

Discussion

In order to be clinically useful, a prediction tool should be well calibrated across the risk spectrum and provide good discrimination between patients with and without the outcome of interest. Overestimation of the likelihood of CAD, in particular, may expose patients to the risks and costs of unnecessary testing and may be partially responsible for the frequently reported low prevalence of obstructive disease in patients undergoing ICA. [2], [11], [12] While several studies have shown

Conclusions

In patients with stable chest pain undergoing CCTA, newer risk factor-encompassing models allow for a more precise estimation of pre-test probabilities of obstructive CAD than the guideline-recommended MDF method. Adoption of these scores may improve disease prediction and change the diagnostic pathway in a significant proportion of patients.

The following are the supplementary data related to this article.

Supplementary tables

. Receiver-operating characteristics curves of the three models

Grant support

None.

Conflicts of interest

The authors report no relationships that could be construed as a conflict of interest.

References (22)

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This author takes responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.

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