A World Health Organization (WHO) survey used to measure general disability can accurately gauge the specific challenges that many patients face postoperatively, a multinational team of researchers has reported. The finding is important because there has been no universal way to assess the level of disability that patients may experience postoperatively. Fully 20% of elderly patients struggle with one or more serious complications after surgery, the researchers noted.
The WHO Disability Assessment Schedule (WHODAS) 2.0, when applied to measuring disability after surgery, demonstrated a good correlation with established tests measuring activities of daily living, quality of life and pain interference scores. While WHODAS is a widely respected measure of disability, it had not been used previously to measure disability after surgery.
The multicenter, multinational study included over 500 patients from The Alfred Hospital and Monash University, in Melbourne, Australia; the Monash-Epworth Rehabilitation Research Centre, in Richmond, Australia; and The Chinese University of Hong Kong, Prince of Wales Hospital.
Currently, there is no gold-standard “patient-centered, long-term outcome measure after surgery,” the researchers noted. “WHODAS is a clinically acceptable, valid, reliable and responsive instrument for measuring disability in a surgical population,” the study stated.
The researchers, led by Mark A. Shulman, MB, an anesthesiologist from The Alfred Hospital, first attempted to create their own assessment tool, only to find a better one in the WHO’s disability survey.
The WHODAS is designed to measure disability in patients across the world from varied cultures, looking at aged individuals and those with a wide spectrum of diseases.
The survey asks patients about their limitations over the past month in six major areas: “cognition, mobility, self-care, interpersonal relationships, work and household roles, and participation in society.” The 12-item questionnaire asks patients to assess the degree of difficulty they experienced in a range of activities, from attending worship services to washing their entire body, dressing themselves and maintaining friendships.
Study participants were provided with the WHODAS questionnaire. They were also given four other surveys that are currently used to assess particular aspects of health after major medical issues: the 40-item quality of recovery score, or QoR-40; the EQ-5D scale, measuring quality of life; the Katz Index of Independence in Activities of Daily Living, or ADL scale; and the modified Brief Pain Inventory Short Form, or mBPI-SF, which measures daily pain.
The aim was to find moderate (but not high) correlations with these other health assessment tests, which measure related but different constructs. The study, published in Anesthesiology (2015;122:524-536), validated the use of WHODAS for measuring postoperative disability by testing the correlation, before and after surgery, between the survey and the other more targeted tests in use.
Preoperatively, there was “moderate correlation” with the Katz ADL scale (r=0.56; P<0.0005) and the QoR-40 score (r=–0.60; P<0.0005). WHODAS also showed modest correlation with the Canadian Study of Health and Aging Clinical Frailty Scale <03C1>=0.28; P<0.0005) and the American Society of Anesthesiologists’ physical status score.
In the early postoperative period, the validity of WHODAS was established by testing the correlation with QoR-40 score after 30 days. That demonstrated a “moderate to strong correlation globally (r=–0.70),” which extended through each part of the scale as well as to subgroups divided by types of surgery and patient age.
At the three-, six- and 12-month mark, the researchers established concurrent correlation between WHODAS and the Katz ADL scale. There was also “good correlation” between WHODAS and mBPI-SF pain scores, which became stronger at three, six and 12 months after surgery.
Convergent validity was also established by correlation between WHODAS and the EQ-5D scale, while “discriminative validity was excellent,” with the disability survey able to distinguish between patients progressing well and poorly after 30 days, and at the three-, six- and 12-month marks.
The survey also had an excellent retention rate, with 88% to 92% of patients completing WHODAS surveys and returning them.
Disability-Free Survival
Having validated WHODAS’s ability to measure postoperative disability, the researchers came to a couple of key conclusions.
First, the WHO disability survey is a “valid and reliable clinical end point,” and it is “well suited for future anesthetic and surgical research.” The test stands out for its simplicity and ease of use, by both patients and doctors.
Second, armed with this new tool, researchers should adopt “disability-free survival” as a “primary end point,” reflecting the “primary goal for most patients undergoing major surgery.” In turn, this has the potential for helping guide discussions with patients facing surgery who must consider the postoperative outlook, aiding “shared decision making.” Disability-free survival as a perioperative outcome measure is the ultimate good result.
“Freedom from disability after surgery is a meaningful outcome for clinicians and patients alike,” the researchers wrote. “We recommend disability-free survival as an important end point in clinical trials.”