Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

INTRODUCTION

Three pain mechanistic phenotypes have been identified- nociceptive, neuropathic, and nociplastic. Evidence suggests that tailoring treatments to pain mechanisms leads to better outcomes than non-targeted strategies.  While there is broad agreement on pain mechanistic phenotypes, the prevalence of these phenotypes in non-specific chronic low back pain (cLBP) has not been well studied.  Defining phenotype prevalence is important both for clinical decision-making as well as for setting research priorities.  The objective of this study was to determine the prevalence of the three primary pain mechanistic phenotypes in a cLBP population.

METHODS

Baseline data from 1,376 participants in BACKHOME, a longitudinal observational e-Cohort of U.S. adults with non-specific chronic LBP (cLBP) that is part of the NIH Back Pain Consortium (BACPAC) Research Program, were analyzed.  Survey data from several domains are collected via an on-line platform.  Back-dominant pain is an eligibility criterion.  Pain locations, number of chronic overlapping conditions (COPC’s), and responses to the PAINDETECT questionnaire were used to define the pain mechanism categories, based on recommendations from a Delphi expert consensus study¹ and from BACPAC investigators.  The categories were nociplastic (≥2 non-lumbar pain regions OR ≥2 COPC’s, PAINDETECT<19), neuropathic (PAINDETECT≥19, <2 non-lumbar pain regions, <2 COPC’s), nociceptive (PAINDETECT<13, <2 non-lumbar pain regions, <2 COPC’s), mixed (not meeting criteria for other categories). 

RESULTS

Participants had the following characteristics: age 54.9 ± 14.4 years, 67.4% female, 60% never smokers, 29.9% overweight, 39.5% obese, PROMIS sleep disturbance t-score 54.8 ± 8.0, PROMIS depression t-score 52.6 ± 10.1, Fear-avoidance Beliefs Questionnaire 11.6 ± 5.9, Pain Catastrophizing Scale 4.5 ± 2.6, PEG (Pain, Enjoyment of Life, and General Activity Scale) 4.4 ± 2.2.  The prevalence of the mechanistic phenotypes is reported in Table 1.

DISCUSSION

The great majority of subjects in this cLBP population have either a nociplastic or nociceptive mechanistic phenotype, each with a similar prevalence.  The low prevalence of the neuropathic pain phenotype likely reflects the study eligibility criteria (back-dominant pain).  While mixed pain mechanisms are considered common, our data does not support that.  A limitation of this study is that mechanistic phenotypes were based on survey data only.  Survey data is essential for assigning mechanistic phenotypes, but some experts consider features derived from physical exam, imaging, and psychophysical testing to be useful.  As there are no gold standards for defining pain mechanisms the validity of methods for discriminating between pain mechanisms cannot be rigorously tested.  Future work should focus on improving the validity of mechanistic phenotypes and, most importantly, defining the ability to predict treatment response.