Every answer, thought, feeling, decision stems from a reference-point. A single value cannot bring meaning to an informed decision. Ex: A 60 degree winter day is warm to those in Boston, and cool to those in San Diego. An increase of strength by 5 lbs is a lot with shoulder external rotation, but not so much with a leg press…. or maybe it is a lot for the leg press in someone recovering from Guillain-Barré. Transporting in a wheel chair does not seem so good, unless you have been bed bound for the previous year. So the reference is an imperative portion of the conversation, the context, if you will.
This complex understanding does not come into play more often than when asking about pain perceptions. “On a scale of 0-10, 10 being the worst imaginable pain, 0 being no pain, how would you rate your *body part*?” Man oh man, where do we even begin?
Without a reference point, 3/10 could be horrible, and 7/10 could be great. Of course we do ask if this is normal, better, or worse for the patient, but we are not truly familiar with their reference-point. What are they comparing this new state to? The patient may feel this second knee surgery hurt worse than the first (selective memory?). Certainly that plays a role in their reference-point. We might assume, that since they have had the procedure before, that they would accommodate easier to this new pain, but that is certainly not always the case.
Now once a new reference-point is established (because in out-patient we must ask about it 2x per visit at least!) how free is that value to budge? Does the patient know that they can go from a 7/10 to a 3/10 in one visit? How does this scale work? What happens when they start to own their pain and experience loss aversion with the scale? Can they give up that number?
Do they understand the scale in a way that we do (ordinal data)? Are the intervals between the values equal to this patient?
As you have guessed, the answer to most of this is NO. There is no set value, it is uncannily subjective and nuanced, and I am floored that a 2 point change in the scale is the MCID. In my world, the drop of 9/10 to 7/10 exhibits different utility than a drop of 4/10 to 2/10. But that is just me… and I’m a 0/10 today.
Here is a wonderful article on low back pain MCID values. From the conclusion:
“In general, improvements ≤ 1.5 [ points on the pain scale] could be seen as irrelevant. Above that value, the cutoff point for clinical relevance depends on the methods used to estimate [MCID] and on the patient’s baseline severity of pain.”
In other words: “it depends.”
In fact, the framing of the whole thing is quite nocebic and angled at the negative. The Brain Trust has often commented that perhaps a placebo version of the scale could be used. “On a scale of 0-10, 10 being the best you’ve ever felt, and 0 being the worst, how good are you doing today?” This in no way solves the subjectivity, but it feels good to get out the pain scale rut.
I am not proposing a solution, and I don’t think we should be looking for a more objective quantifiable measure, for it is the nature of the subject matter (pain) that precludes affirmatives and understanding. The point is this: taking data un-tethered to reference-points on a multivariate input system is like placing a dollar value on a toddler’s artwork.
All that being said, the inquiry into the status of our patients should not cease… and so we will continue to ask, and learn… and to find out what we can about our patient’s perspective reference-point.