The problem with using stairs to assess METs
And a better alternative, the DASI score
The teaching in anesthesia is that if a patient can climb one or two flights of stairs without stopping,1 then the person is at low risk for cardiac complications while undergoing anesthesia. Unfortunately, assessing a person’s functional capacity in this subjective manner is wholly inaccurate.2
Metabolic equivalents (METs) are a measure of the rate of oxygen consumption, with 1 MET being defined as an oxygen consumption of 3.5 mL oxygen/kg/min. Certain activities have been assigned rough MET values. For example, sitting at rest is a baseline 1 MET while playing doubles tennis is estimated at around 5 METs. The problem with asking if a person can climb two flights of stairs is that it confuses total work done with the rate of work.
In physics terms, everyone who walks up two flights of stairs has done the same amount of work (assuming everyone in this example weighs the same). However, the speed at which a person walks up those stairs determines the number of METs achieved. A person walking up two flights of stairs in 15 seconds achieves more METs than someone who takes one minute.
Metabolic equivalents define a rate, whereas asking about walking up two flights of stairs without specifying a time period defines only a total amount of work being done.
The METS study objectively measured patients’ functional capacity and asked anesthesiologists to subjectively assess patients’ METs. They found that subjective assessment had a sensitivity of 19.2% for identifying the inability to attain 4 METs during cardiopulmonary exercise testing (CPET). In other words, many patients who could not attain 4 METs were incorrectly assessed as being able to attain 4 METs.
If asking about climbing stairs is pointless (i.e., inaccurate), what can we do instead?
The authors of the METS study also assessed functional capacity using the Duke Activity Status Index (DASI) questionnaire. Although it is also a subjective assessment, higher DASI scores were associated with a lower risk of the primary outcome of death or myocardial injury in patients undergoing noncardiac surgery (adjusted odds ratio, 0.96; 95% confidence interval, 0.83-0.99; p = 0.03).3
The latest American Heart Association (AHA) perioperative guidelines published in 2024, now recommend using the DASI score to assess functional capacity. They treat a score ≥ 35 as equivalent to achieving ≥ 4 METs.
Completing the DASI questionnaire is slower, but that could be mitigated by having patients fill it out with their preoperative paperwork or by integrating it into the electronic medical record (EMR) as calculator.
Subjectively assessing functional status will always be somewhat imprecise. However, the DASI score gives us a much more accurate tool to do so than simply asking people if they can walk up stairs.4
Should it be one or two flights? I’ve read both. Interestingly, a 2022 study found three flights of stairs to be most closely associated with achieving 4 METs.
I get excited when I see stress test results that list the number of METs a patient achieved.
Let’s not overlook how close the confidence interval for the odds ratio is to 1.0. A 2025 study compared DASI to CPET and found only a moderate correlation (Spearman’s rho = +0.620, p < 0.001) with the DASI score overestimating patients’ METs.
The MET-REPAIR questionnaire is another more accurate assessment of functional status and it performed similarly to the DASI.