March 9th, 2015

Appropriate Use Criteria for Diagnostic Catheterization are Weak

Appropriate use criteria (AUC) are designed to help make sure that medical procedures and interventions are performed in patients most likely to benefit and, in turn, are not performed on people unlikely to gain benefit. Now a new study published in Annals of Internal Medicine suggests that the AUC for one very widely performed procedure, diagnostic cardiac catheterization, can provide a very rough indication of when it should and should not be performed, but that a great deal more work needs to be done before the criteria can be considered broadly reliable.

Researchers in Canada analyzed data from 18 hospitals in Canada including 48,336 patients with no known history of coronary artery disease who underwent diagnostic catheterization. Using criteria established by the American College of Cardiology in 2012, 58.2% of the procedures were considered appropriate, 31% were uncertain, and 10.8% were inappropriate.

A key measure was the diagnostic yield, or the percentage of people with a significant finding requiring further action. The percentage of patients who were found to have  obstructive CAD was 52.9% in the appropriate group, 36.7% in the uncertain group, and 30.9% in the inappropriate group. The percentage of patients with significant left main or triple-vessel disease was 16.5%, 8.7%, and 7.1%. A revascularization procedure was performed in 40%, 25.9%, and 18.9%.

“Angiography in patients with an appropriate indication was associated with improved diagnostic yield of obstructive CAD and left main or triple-vessel disease and more subsequent revascularization. However, a substantial proportion of patients with inappropriate or uncertain indications also had important CAD,” the authors wrote. “Our finding that angiography with appropriate indications detects a greater proportion of obstructive CAD offers support to the AUC. However, it is important to note that our study also shows that almost 42% of the patients with appropriate studies did not have obstructive CAD, more than 30% of those with studies classified as inappropriate had obstructive CAD, and almost 19% of those in the inappropriate category had subsequent revascularization within 90 days.”

“Unfortunately, our results suggest that although the AUC provides some insight, it is insufficient in isolation to select patients who either should or should not undergo diagnostic angiography,” said the senior author of the study, Harindra Wijeysundera, in an interview with the editors of CardioExchange. “Our study highlights the need to further refine the AUC to better guide patient selection.”

In an accompanying editorial, Jacob Doll and Manesh Patel ask: “What about the 47% of procedures rated appropriate that did not find obstructive disease? It is important to recognize that not all indicated angiographic studies uncover CAD. Rather, the appropriateness rating indicates that the clinical scenario is one for which evidence supports a benefit of performing invasive angiography. A finding of no CAD in a patient with a high pretest probability, with resultant avoidance of unnecessary medications and further testing, is a valuable result. Similarly, the finding of obstructive disease among some patients with procedures rated inappropriate is expected.”

CardioExchange editor John Ryan offered additional perspective on the study: “This is an important manuscript because it raises concerns about the role of appropriate use criteria in diagnosing coronary artery disease with angiography. It is concerning that although ~10% of coronary angiograms were deemed inappropriate by AUC, ~20% of these patients required revascularization, and ~7% had left main disease. Of note, this study excluded people with MI, ACS, valvular heart disease, known CAD, prior revascularization, and arrhythmia. So it is a very select cohort under study here. Therefore the generalizability of these findings to a U.S. population is uncertain, but it sheds light on the challenges facing physicians, payers, and patients, in deciding what is appropriate and inappropriate. It will be important to extend this analysis into other aspects of diagnostic testing, including the AUC laid out for stress testing and echocardiography, among others.”

Note: Comments on this news story are closed, but please join the discussion about this topic over at our interview with Harindra Wijeysundera, lead author of this study.


One Response to “Appropriate Use Criteria for Diagnostic Catheterization are Weak”

  1. Brett Forge, MB BS FRACP says:

    This is an invasive and expensive test. Defining appropriateness based on the finding of coronary disease is NOT a criteria for appropriateness without answering the question if a less expensive and invasive test can give the same or better results. And furthermore can less expensive and invasive tests reduce the number of negative tests. In fact CT coronary angiography is much cheaper, less invasive and even provides information about plaque (unlike invasive angiography). CTCA can exclude left main and confirm the diagnosis and the only proven treatment (lifestyle change, statins, aspirin and possible beta blockers) can be initiated. Coronary angiography is not needed in the great majority. Only pts found to fail medical treatment will need consideration for PCI.

    Simple stress testing in low risk patients will exclude a large number of patients who do not need any further investigation