VICTORIA, B.C. – Physician and patient assessments of disease activity in rheumatoid arthritis show considerable disagreement that seems to be driven by subjective perceptions of pain, a study has shown.
The study involved nearly 900 patients with early rheumatoid arthritis (RA) and 100 patients with established RA in remission, all of whom had been treated only with disease-modifying antirheumatic drugs (DMARDs). Findings on physician and patient assessments of disease activity disagreed to a clinically meaningful extent roughly one-fourth to one-third of the time, based on the results of this as-yet unpublished study, reported at the annual meeting of the Canadian Rheumatology Association.
In most cases of discordance, patients rated their RA as being worse than their physicians did. Findings from additional analyses suggested that the discrepancy was largely due to subjective pain, and pain levels showed some association with cumulative RA-related joint damage.
"For a rheumatologist who is using these global assessment scores" – the patient global assessment (PtGA) and the physician global assessment (MDGA) – "75% of the time, you can expect the patient to agree with you on their disease activity level. They are going to report a pretty similar score. But for the other 25% of the time, the patient’s going to say, ‘My disease is worse than what you think it is,’ " explained presenting author May Choi, a second-year medical student at the University of Alberta, Edmonton.
"We think it’s more a reflection of their subjective pain, and that pain is probably not in their joints – it probably has something to do with soft tissue pain, like fibromyalgia," she added. In patients with established disease, the pain appears to reflect "all of the joint damage they have accumulated over the years because of the RA. So it’s not a reflection of their current disease activity, but the damage that has resulted."
Physicians who find a discrepancy between assessments for a given patient should take a closer look to determine the reason, especially as it has implications for treatment, Ms. Choi advised in an interview. "If a patient is in a lot of pain, but a physician is feeling their joints and they don’t really see [an explanation for] what’s going on, they are not going to give them a drug for their joints. They are going to look at other reasons and treat them for that – pain that’s related to their soft tissues," she explained.
The study’s findings also suggest that the two assessments are complementary, and both should be used, she maintained. "I don’t think one is more important than the other. They provide different information" and in clinical studies, "absolutely, they should get both numbers to get the big picture."
Previous research has found a difference between physician and patient global assessments of RA disease activity, but the reason remains unknown, according to Ms. Choi. "This is an important question because physicians use this tool to monitor their patients, and we think it’s important to increase awareness that there is a difference. We wanted to look at reasons why this difference exists and what are its implications for patient management," she said.
For the study, which was supported by the Canadian Rheumatology Association–Roche Summer Studentship, the researchers identified 897 patients with early RA (mean disease duration, 0.5 years) from the Canadian Early Arthritis Cohort database and 100 patients with established RA in remission from one practice (mean disease duration, 18 years).
Scores were compared from the patient-completed PtGA and physician-completed MDGA. Discrepancy between results on the two 100-mm scales was assessed by subtracting the latter from the former and was classified as clinically meaningful if it was at least 30 mm.
Study results, reported in a poster session, revealed that in the early RA group, the PtGA and MDGA scores showed no discrepancy in 64% of patients. But in 24%, patients reported worse disease than their physicians did, and in 12%, physicians reported worse disease than patients did.
Compared with their counterparts having no discrepancy, patients over-reporting disease activity had lower swollen and tender joint counts and similar C-reactive protein levels. Yet they also reported more pain. "So here is a group of patients who are reporting a lot of pain, but it’s not in their joints necessarily," commented Ms. Choi. On the other hand, compared with their counterparts having no discrepancy, patients underreporting disease activity had higher swollen joint counts and C-reactive protein levels, and yet less pain. This finding may be related to differing pain thresholds across individuals, she noted, saying, "There are some patients like that. They are just not as sensitive."