When it comes to predicting disabilities in frail patients after elective noncardiac surgery, the Clinical Frailty Scale (CFS) and the modified Fried Index (mFI) prove generally comparable. Where the two tools diverge, however, is in their ease and speed of administration, which seems to favor the CFS, according to researchers at the University of Ottawa.
“It doesn’t matter which frailty tool you use. If you identify someone as frail before surgery, they will very likely have poor outcomes after surgery,” said Daniel I. McIsaac, MD, MPH, FRCPC, assistant professor of anesthesiology and pain medicine, University of Ottawa, who is an adjunct scientist at the Institute for Clinical Evaluative Sciences, in Toronto.
“The problem is there are [seemingly] hundreds of different frailty instruments available. This becomes an issue in the perioperative setting because we have no data to compare these instruments for clinical use before surgery, so we don’t know which one to use.”
A comparison becomes more important in light of previous research, which has shown that 25% to 40% of adverse events in patients over 65 years of age are attributable to frailty (Can J Anaesth2015;62:143-157). “We wanted to address this knowledge gap and do a comparative assessment of two leading instruments to risk-stratify older patients before surgery,” Dr. McIsaac said.
The investigators recruited a total of 680 patients—all of whom were at least 65 years of age and undergoing elective inpatient noncardiac surgery—into the multicenter prospective cohort study. Frailty status was measured preoperatively using either the CFS or the mFI.
“The Clinical Frailty Scale is a vignette-based, subjective assessment based on nine distinct points,” Dr. McIsaac explained at the 2017 annual meeting of the Canadian Anesthesiologists’ Society (abstract 284220). “Patients that score 4 or greater are considered frail, based on most definitions in the literature.
“The modified Fried Index, on the other hand, is currently recommended by the American Geriatrics Society and the American College of Surgeons,” he said. “It includes asking your patient how easily they get exhausted, whether they’ve had falls in the past six months, and whether they’ve had unintentional weight loss.” The mFI also incorporates grip strength and gait speed tests. The study’s primary outcome was new disability at 90 days after surgery, using the World Health Organization Disability Assessment Schedule 2.0 tool.
The researchers found that new disabilities were present in 11.2% of all participants. Based on the CFS, 42% of patients were deemed to be frail, compared with 36% for the mFI. There was moderate agreement between the two scales, consistent with previous findings in the literature.
“Sixteen percent of patients deemed frail based on CFS criteria developed a new disability at 90 days after surgery, compared with 18% of those deemed frail by the mFI,” Dr. McIsaac said. “If you look at odds ratios, frail patients were about 3.0 times more likely to develop a new disability with the CFS and 3.5 times with the mFI.”
The CFS was found to be 77% sensitive and 54% specific for new disability, compared with 13% and 84%, respectively, for the mFI. When tested as linear terms, each unit increase on the CFS was associated with a 1.71-fold increase in the odds of new disability (95% CI, 1.26-2.32). By comparison, each increase in the mFI increased the same odds by 1.64 times (95% CI, 1.18-2.29).
The two tools also proved comparable with respect to true positive rates. “There was a bit of a higher false-positive rate with the CFS, which was statistically significant,” Dr. McIsaac said. “So that test will identify a few more people as frail, even though they’ll end up doing OK after surgery anyway.”
Despite their relative comparability, the tests diverged with respect to one important characteristic: their ease of administration. Indeed, while it took the researchers approximately 30 seconds to administer the CFS, the mFI needed about five minutes to be completed. “That was also reflected in the fact that we had completed the Clinical Frailty Scale data on every single patient in our study,” Dr. McIsaac said. “Yet almost one in five patients undergoing the modified Fried Index refused to perform one of the quantitative measures. And that, I think, is one of the most important findings of the study.
“So if I’m screening people for relatively low-tech preoperative interventions, I’m personally going to use the CFS because I know I’m going to get it done on everybody and get it done quickly,” he said. “I can say that at our institution, I simply added it to our preoperative manager, and 60% of people started using it.
“If you want a more specific tool, the mFI is a bit more specific, but you’re going miss a few people who won’t complete it. But like any screening test, the ultimate decision is going to depend on your purpose for screening.”
Session moderator Stephen Kowalski, MD, associate professor of anesthesia at the University of Manitoba, in Winnipeg, was impressed with the practicality of the CFS. “This is clearly an important topic to all of us,” Dr. Kowalski said. “On a practical point, I like the CFS. And when we’re seeing patients in the preoperative clinic, they’re not happy if they have to stay any longer than is necessary.”
On the other hand, Peter Moliner, MD, adjunct professor of anesthesiology at the University of Sherbrooke, in Quebec, did not take such an optimistic view. “I don’t want to be too cynical, but you’re basically noting that people who are sick get sicker,” Dr. Moliner said. “That’s not a surprise. Obviously, the question is where are we going to go with this. What’s the next step, and what’s the intervention we’re going to implement as a result?”
“That’s a very relevant question,” Dr. McIsaac replied. “The fact is that frail patients have very different outcome trajectories than other pat ients undergoing surgery, even if they are of the same ASA class. They have a higher rate of early mortality, and also suffer from geriatric-specific outcome trajectories, like loss of independence and cognitive dysfunction.
“So the reason we should care about frailty is that it identifies a fairly homogeneous high-risk strata of our population, to whom we can apply relatively homogeneous interventions.”