A new study presented at the 63rd Annual Meeting of the Society for Vascular Surgery confirms the effectiveness of a simple and reliable tool that can predict the risk of amputation-free survival (AFS) for patients with critical limb ischemia (CLI).
Known as the Schanzer PIII CLI risk score, this score is used to risk stratify CLI patients being considered for infrainguinal bypass into low-, medium- and high-risk categories. At initial consultation, five easily obtainable binary variables (dialysis-dependency, tissue loss, advanced age, advanced CAD and low hematocrit) can be obtained. Patients with a 50% chance of death or major amputation at 1 year can be identified prior to undergoing surgery. In addition, a valid estimate can be made as to the likelihood that a patient will be alive with the bypassed limb intact at 1 year after surgical revascularization.
Researchers validated this risk stratification model using the prospective Vascular Study Group of Northern New England (VSGNNE) database and calculated the PIII CLI risk score for 1,579 patients receiving infrainguinal bypass.
“The strength of the VSGNNE dataset stems from its enrollment base — 49 different private and academic surgeons at 11 community and university hospitals — which provides heterogeneity and a depiction of “real-world” practice patterns,” Andres Schanzer, MD, assistant professor in the division of vascular and endovascular surgery at the University of Massachusetts Medical School in Worcester, said in a news release.
Using this database, the PIII CLI risk score has now been tested against the outcomes of 3,286 CLI patients who underwent open surgical bypass at 94 institutions by a diverse array of physicians.
“The present validation study builds on previous reports by extending the overall generalizability of this risk score,” Schanzer said. “As a result, we believe that the PIII CLI risk score is a useful clinical tool for surgical decision-making and for patients to better understand the possible risks of open surgical bypass.”
Researchers said that the original model’s performance was initially derived and validated in a select population of patients who were participants in a randomized trial. It then was further validated in a multi-center retrospective cohort assembled from three different hospitals.
“Despite the heterogeneity and a dramatically different patient cohort than the one from which the model was originally derived, the 1-year amputation-free survival estimates for each risk category are remarkably similar,” Schanzer said.
Researchers said that the PIII CLI risk score also may be useful for quality improvement initiatives. As the model has now been extensively validated, they believe the expected 1-year AFS rates can be calculated for a given dataset and these estimates can be used to create specific risk-adjusted benchmarks for individual practitioners or centers.
“In the same way that the National Surgery Quality Improvement Program has created observed to expected ratios for participating centers, the PIII CLI risk score can be used to generate accurate comparative outcomes for patients undergoing bypass for CLI,” Schanzer said. “With an enhanced awareness of risk-adjusted outcomes at distinct centers, efforts could be directed at identifying individual factors and processes of care that contribute to these improved outcomes. Once identified, these processes could be promoted and implemented elsewhere in order to improve the overall quality of care for the CLI population.”
