A few posts ago I reported the results of a quick and dirty survey we ran online a few months back that was intended to get at the degree to which people indicated what property of a pain experience is more important to their sense of wellness or disability: the intensity of the pain or other symptoms, or the frequency with which those symptoms are experienced. You can read the post about the results from the main Blog Central page, but in a nutshell the survey results appeared to lean towards frequency of experience being a more important influence than the intensity or severity of the experience. This of course didn't come out of thin air, it's something that we hear at the PIRL have been thinking about and working on for some time now. Back in 2013 we published the results of a series of interviews and focus groups in which we tried to explore the concept of recovery and what that would mean to people with neck pain. Not surprisingly 'absent or manageable symptoms' was a consistent theme from these discussions (recently independently reproduced by Carroll and colleagues). But when the phrases were explored more deeply, we realized that what many of our respondents were getting at wasn't the intensity of pain, but the frequency with which they experienced it. And it wasn't just pain, in fact we identified at least 10 different broad classes of symptoms that people with chronic neck pain were experiencing, from pain and stiffness through to weakness, fogginess, sensitivity to light or odor right to fatigue and negative emotions. It also was quite clear that the problem with intensity was more about what the symptoms prevented people from doing (interference). So, recognizing that the frequency and interference resulting from a number of different symptoms appears to be important to patients, we set out to find a PRO that would cover these things. It will likely be surprising to no one that we found none. The year was 2012 and we set out to therefore create the 3rd in what would ultimately become a trilogy of new PROs for predicting and measuring chronic pain and disability following acute MSK injuries.
Being the newest of the 3 (the others being the Satisfaction and Recovery Index that can be found here and the Traumatic Injuries Distress Scale that is currently under review for publication) the Multidimensional Symptom Inventory is not yet quite ready for prime time. So far we've collected 96 responses on the new tool, that provides 3 primary indices (number of symptoms experience /10, mean frequency of those symptoms /3, mean interference caused by those symptoms /4) and 2 secondary indices (the product of frequency x intensity for each symptom, and a regression-weighted Symptom Index that incorporates all 3 of the primary indices). In the interest of making this post not overly long I'll cut to the chase: in our regression analyses where region-specific disability (e.g. NDI, RMQ, LEFS, UEFI) or health-related satisfaction (SRI) are the dependent variables, mean frequency is coming out as a much stronger explanatory variable for disability and satisfaction than is the intensity/interference parameter. And, in the 23 people for whom we've also collected 3 month data, same deal - we can predict outcome using the baseline frequency parameter far better than using the intensity parameter.
We're continuing to collect data on the new MSI tool and will publish it once we feel it's ready, but for now I'd encourage clinicians to include some measure of symptom frequency in addition to the routine of intensity NRS, and also don't forget that body diagram for location!