Differential risk reclassification improvement by exercise testing and myocardial perfusion imaging in patients with suspected and known coronary artery disease

Abstract

Risk reclassification by diagnostic testing is importantly influenced by baseline characteristics of patient cohorts. In patients with suspected CAD, NRI is predominately achieved by exercise variables, whereas in patients with known CAD, greatest NRI is obtained by MPI variables.

The benefits of advanced risk reclassification

“…8 This report noted that when exercise testing and myocardial perfusion SPECT data were added to a model including the Framingham risk score, there was a significant improvement in the NRI; with values of 9.6% for the Duke treadmill score and 14.7% for nuclear imaging data. 8 One key difference between these two reports is that the latter series had more substantial follow-up (median of 6.9 years) compared to 2.5 years in the Koh 7 series. Longer-term follow-up findings can often yield varied findings as to the effectiveness of prognostication, in particular in lower-risk patient cohorts.…”

“…Higher NRI calculations for stress PET imaging data estimating cardiac mortality have been reported for men (NRI: 0.17) and older women (NRI: 0.21). 6 7 report provided a unique approach by formulating three models including the base comparator of a clinical model compared to a model adding the DTS, and then a third model of MPI variables. This demonstrates the incremental value of adding the DTS or data derived from MPI to baseline clinical risk factors in risk assessment.…”

“…The NRI analysis requires that discrete categories of outcome rates are clearly defined. For example, in the Koh 7 series, the all-cause death rates were categorized as \1%, 1-3%, and [3% per year. Similar cutpoints were used in a PET analysis estimating cardiac mortality.…”

“…This approach has now been successfully applied in a number of prognostic analyses using nuclear imaging. [3][4][5][6][7][8][9] Although most reports quantifying the overall NRI have reported that nuclear variables add considerably to the ability to accurately detect low-and high-risk individuals, in this issue of the journal, Koh and colleagues 7 reported intriguing results from a relatively large, singlecenter database of 6702 patients referred for exercise myocardial perfusion imaging (MPI) for either suspected or known coronary artery disease (CAD). This report provided a unique approach by formulating three models including the base comparator of a clinical model which was then compared to a model adding the Duke Treadmill Score (DTS), and then a third model adding the summed difference score and a categorical post-stress left ventricular ejection fraction variables.…”

“…The Koh 7 series reminds us that the use of stress MPI should be used in appropriately selected groups. At the heart of any diagnostic test is to select the best test that will provide additional information impacting management and improving clinical outcomes while minimizing cost and patient risk.…”