Pain phenotyping and investigation of outcomes in physical therapy: An exploratory study in patients with low back pain

Abstract

Phenotypes have been proposed as a method of characterizing subgroups based on biopsychosocial factors to identify responders to analgesic treatments. This study aimed to, first, confirm phenotypes in patients with low back pain receiving physical therapy based on an a priori set of factors used to derive subgroups in other pain populations. Second, an exploratory analysis examined if phenotypes differentiated pain and disability outcomes at four weeks of physical therapy. Fifty-five participants completed psychological questionnaires and pressure pain threshold (PPT). Somatization, anxiety, and depression domains of the Symptom-Checklist-90-Revised, and PPT, were entered into a hierarchical agglomerative cluster analysis with Ward’s method to identify phenotypes. Repeated measures ANOVAs assessed pain ratings and disability by phenotype at four weeks. Three clusters emerged: 1) high emotional distress and pain sensitivity (n = 10), 2) low emotional distress (n = 34), 3) low pain sensitivity (n = 11). As an exploratory study, clusters did not differentiate pain ratings or disability after four weeks of physical therapy (p’s>0.05). However, trends were observed as magnitude of change for pain varied by phenotype. This supports the characterization of homogenous subgroups based on a protocol conducted in the clinical setting with varying effect sizes noted by phenotype for short-term changes in pain. As an exploratory study, future studies should aim to repeat this trial in a larger sample of patients.

General and Pain‐Associated Psychological Distress Phenotypes Among Patients With Low Back Pain in the Military Health System

“…Numerous studies have conducted phenotyping analyses in patients with LBP using a variety of methods and patient-level variables. 27,[53][54][55] For chronic LBP specifically, a recent systematic review found 43 studies, 56 with the number of phenotypes identified ranging from two to nine per study. 54,56 The large majority of studies identified three to four phenotypes.…”

“…Our sample included patients with varying acuity of LBP, likely increasing its applicability for primary care settings that see a spectrum of patients with acute to chronic presentations. Prior studies have explored LBP phenotypes in cohorts representing worker's compensation, 53 university‐based health systems, 27 and county 1,54 and national osteoarthritis registries 55 . None have assessed phenotypes in beneficiaries of the MHS.…”

“…26 Prior studies in populations with LBP, including those designed to identify clinical phenotypes, have focused primarily on a limited number of individual psychological characteristics such as trait anxiety, depression, or pain catastrophizing. 10,14,27 These include studies using the Start Back Risk Screening tool for delivering riskstratified care for LBP. [28][29][30] These approaches fail to appreciate the complexity of psychological profiles, which include unique additional constructs, such as fear avoidance beliefs, pain-related anxiety, and self-efficacy.…”

“…The full extent of psychological distress and the nature of its interaction with LBP outcomes remains unclear 26 . Prior studies in populations with LBP, including those designed to identify clinical phenotypes, have focused primarily on a limited number of individual psychological characteristics such as trait anxiety, depression, or pain catastrophizing 10,14,27 . These include studies using the Start Back Risk Screening tool for delivering risk‐stratified care for LBP 28–30 .…”

Patient-reported outcome measures in physical therapy practice for neck pain: an overview of reviews

“…The evaluation of multiple domains of psychological distress including depression, anxiety, and pain catastrophizing allows for increased effectiveness and efficiency in discriminating between patients who may be at risk for poor outcomes. This comprehensive evaluation also allows for classifying pain phenotypes and identifying those who would benefit from targeted treatment interventions such as cognitive behavioral therapy or psychologically informed treatment [77][78][79]. Due to this, considering a multidimensional tool which evaluates a global psychological profile would inform a clinician if specific targeted interventions would be beneficial for their patient.…”