- Note that this large, cross-sectional study of European patients with knee osteoarthritis found that a significant percentage reported inadequate pain relief.
- Be aware that opioid use was associated with a greater likelihood of inadequate pain relief.
Inadequate pain relief (IPR) is widespread among patients with knee osteoarthritis (OA), especially women, those with depression or diabetes, and those who have had the disease for a long time, according to a new prospective, longitudinal cohort study.
In a large group of patients with knee OA, 54% met the definition of IPR, which was a score of >4 on the Brief Pain Inventory (BPI) scale, according to Philip G. Conaghan, Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, England, and colleagues.
“The fact that 54% of patients in this real-world setting had persistent moderate to severe pain suggests that currently prescribed pain treatments for knee OA are not meeting the needs of the majority of patients,” they wrote in an article published in Rheumatology.
The prevalence of IPR could be as high as 70% if a pain score of =3 on the BPI (no worse than mild pain) was used as a treatment target, said the researchers.
The Survey of Osteoarthritis Real World Therapies (SORT) was carried out at 53 centers in six European countries. The analysis included 1,187 patients with knee OA who were prescribed topical or oral pain medication within the previous 2 weeks. They were recruited from November 2011 to January 2012.
The mean age of participants was 67.8 years and 68.1% were female. The most common comorbidity was hypertension, affecting 58.3% of patients. Just over half (52.2%) of the subjects had OA affecting both knees while almost a quarter had an affected left knee (24.1%) or right knee (23.8%).
Study participants assessed average OA pain using question 5 of the BPI, which rates pain on a scale of 0-10. A score of 0-4 is defined as mild pain; 5-6 as moderate pain; and 7-10 as severe pain.
Patients also assessed their pain, stiffness, and physical function in the knee using the Western Ontario and McMaster (WOMAC) osteoarthritis index. As well, they reported their quality of life and satisfaction with symptomatic treatment for knee OA.
The study found that the prevalence of IPR (54%) as determined by patient responses to the BPI average pain question was well correlated with the WOMAC pain subscale (P <0.001), “further demonstrating that the concept of IPR is not an artifact of how IPR is defined and assessed,” wrote the authors.
The IPR and non-IPR groups differed in many respects. IPR patients were more likely to be female (adjusted odds ratio [adjOR] 1.90, 95% confidence interval [CI] 1.46-2.48), and to have a longer disease duration, greater opioid use and co-morbid hypertension, depression, and diabetes.
“Clinicians should recognize this constellation of characteristics as constituting special risk,” said the authors.
As well, a significantly greater percentage of patients with IPR had OA affecting both knees (P<0.001) and partial or total disability (P=0.009) compared with the non-IPR group.
The most commonly prescribed analgesic was a nonsteroidal anti-inflammatory drug (NSAID) (65.1%), followed by paracetamol (39.6%,) and opioid drugs (21.4%). IPR patients were more likely than non-IPR patients to be prescribed paracetamol or opioid-containing medications.
These findings, said the authors, indicate that “management of OA in primary care may not conform to the recommendations in clinical practice guidelines or to the intensity of patients’ pain.”
The study also showed that, overall, 51% of the IPR group reported their general health status to be fair or poor compared with 31% of the non-IPR cohort (P<0.001). At baseline, 48% of patients with IPR reported dissatisfaction with response to treatment and 38% reported dissatisfaction with tolerability of medication.
Since not all invited patients consented to participate in the study, selection bias is a possible limitation. And as the analysis is cross-sectional, the causal link between IPR and functional status can’t be fully characterized.
Paul M. Peloso was a full-time employee of Merck at the time this study was designed and conducted; Ceri J. Phillips has received honoraria from Merck.
Christopher M. Black is an employee of Merck; Francois Rannou has received honoraria from MSD for the SORT study.
Srinivasan Rajagopalan has worked as a consultant on this project and others at MSD.
Stephanie D. Taylor, Sharlette V. Everett, and Panagiotis Mavros are employees of MSD and is a shareholder of Merck & Co., Inc.
Mart AFJ van de Laar has provided consultancy services to Pfizer, Novartis, and MSD and has received research grants from AbbVie, Pfizer, MSD, BMS, and Roche.
The other authors have declared no conflicts of interest.
F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner