What General and Pain-associated Psychological Distress Phenotypes Exist Among Patients with Hip and Knee Osteoarthritis?
Authors: Lentz Trevor A. , George Steven Z. , Manickas-Hill Olivia , Malay Morven R. , O’Donnell Jonathan , Jayakumar Prakash , Jiranek William , Mather Richard C. 
Published: October 2020

Abstract

Background
Psychological distress can negatively influence disability, quality of life, and treatment outcomes for individuals with hip and knee osteoarthritis (OA). Clinical practice guidelines recommend a comprehensive disease management approach to OA that includes the identification, evaluation, and management of psychological distress. However, uncertainty around the best psychological screening and assessment methods, a poor understanding of the heterogeneity of psychological distress in those with OA, and lack of guidance on how to scale treatment have limited the growth of OA care models that effectively address individual psychological needs.

Questions/purposes
(1) Across which general and pain-related psychological distress constructs do individuals seeking conservative care for hip or knee OA report higher scores than the general population of individuals seeking conservative care for musculoskeletal pain conditions? (2) What common psychological phenotypes exist among nonsurgical care-seeking individuals with hip or knee OA?

Methods
The sample included participants from the Duke Joint Health Program (n = 1239), a comprehensive hip and knee OA care program, and the Optimal Screening for Prediction of Referral and Outcome (OSPRO) cohort studies (n = 871) comprising individuals seeking conservative care for knee, shoulder, low back, or neck pain. At the initial evaluation, patients completed the OSPRO Yellow Flag (OSPRO-YF) Assessment Tool, which assesses 11 general and pain-related psychological distress constructs (depression, anxiety, fear of movement, self-efficacy for managing one’s own pain). We used OSPRO-YF scores to compare levels of psychological distress between the cohorts. Cohen’s d effect sizes were calculated to determine the magnitude of differences between the groups, with d = 0.20, d = 0.50, and d = 0.80 indicating small, medium, and large effect sizes, respectively. We used a latent class analysis to derive psychological distress phenotypes in people with OA based on the 11 OSPRO-YF psychological distress indicators. Psychological distress phenotypes are characterized by specific mood, belief, and behavioral factors that differentiate subgroups within a population. Phenotyping can help providers develop scalable treatment pathways that are better tailored to the common needs of patients.

Results
Patients with OA demonstrated higher levels of general and pain-related psychological distress across all psychological constructs except for trait anxiety (that is, anxiety level as a personal characteristic rather than as a response to a stressful situation, like surgery) with small-to-moderate effect sizes. Characteristics with the largest effect sizes in the OA and overall OSPRO cohort were (Cohen’s d) general anxiety (-0.66, lower in the OA cohort), pain catastrophizing (the tendency to ruminate over, maginfiy, or feel helpless about a pain experience, 0.47), kinesiophobia (pain-related fear of movement, 0.46), pain self-efficacy (confidence in one’s own ability to manage his or her pain, -0.46, lower in the OA cohort), and self-efficacy for rehabilitation (confidence in one’s own ability to perform their rehabilitation treatments, -0.44, lower in the OA cohort). The latent class analysis yielded four phenotypes (% sample): high distress (52%, 647 of 1239), low distress (26%, 322 of 1239), low self-efficacy and acceptance (low confidence in managing and willingness to accept pain) (15%, 186 of 1239), and negative pain coping (exhibiting poor pain coping skills) (7%, 84 of 1239). The classification error rate was near zero (2%), and the median of posterior probabilities used to assign subgroup membership was 0.99 (interquartile range 0.98 to 1.00), both indicating excellent model performance. The high-distress group had the lowest mean age (61 ± 11 years) and highest levels of pain intensity (6 ± 2) and disability (HOOS JR: 50 ± 15; KOOS JR: 47 ± 15), whereas the low-distress group had the highest mean age (63 ± 10 years) and lowest levels of pain (4 ± 2) and disability (HOOS JR: 63 ± 15; KOOS JR: 60 ± 12). However, none of these differences met or exceeded anchor-based minimal clinically important difference thresholds.

Conclusions
General and pain-related psychological distress are common among individuals seeking comprehensive care for hip or knee OA. Predominant existing OA care models that focus on biomedical interventions, such as corticosteroid injection or joint replacement that are designed to directly address underlying joint pathology and inflammation, may be inadequate to fully meet the care-related needs of many patients with OA due to their underlying psychological distress. We believe this because biomedical interventions do not often address psychological characteristics, which are known to influence OA-related pain and disability independent of joint pathology. Healthcare providers can develop new comprehensive hip and knee OA treatment pathways tailored to these phenotypes where services such as pain coping skills training, relaxation training, and psychological therapies are delivered to patients who exhibit phenotypes characterized by high distress or negative pain coping. Future studies should evaluate whether tailoring treatment to specific psychological phenotypes yields better clinical outcomes than nontailored treatments, or treatments that have a more biomedical focus.

Level of Evidence
Level III, diagnostic study.