Study: Patient Global Assessment Scores Give Insight Into Daily Function

Study Design

Dr. Craig

In their study, Dr. Craig and colleagues tapped two observational cohorts comprising more than 450 RA patients. Most patients were seropositive with established disease, and more than two-thirds were in remission or in a state of low disease activity.

Participants completed various patient-reported outcome measures of health-related quality of life (including the patient global assessment) using either short forms or computer adaptive testing. The patient global assessment was phrased in terms of global health. Measures of disease activity were assessed clinically (such as through DAS28), and the inflammatory markers ESR and CRP were also collected.¹

The team used factor analysis to identify the underlying dimensions that may be driving the associations between findings (e.g., between fatigue and sleep disturbance) and thus underlying trends in the patient global assessment.

“Factor analysis is a data reduction strategy in this application,” explains Dr. Craig. “It’s essentially finding correlated variables, then grouping them into a factor and identifying how strongly each variable relates to the theoretical factor.”

Using multivariable linear regression, the researchers could then estimate the determinants of the patient global assessment using these factors.¹

Study Findings & Interpretation

Using these analyses, two latent factors stood out in the data. The “daily function factor” included large components of physical function, pain interference, social participation and fatigue. “That tells us these features travel together,” explains Dr. Craig. This factor explained up to 53% of the variation in the patient global assessment. In both cohorts, the daily function factor independently predicted the patient global assessment score, as did swollen joint count, to a lesser extent.¹

Another factor, emotional distress, included primarily depression and anxiety, and was not independently associated with the patient global assessment when adjusted for the daily function factor and other covariates. It explained about 15% of the variance in the patient global assessment.¹

Dr. Craig admits the study has some limitations in its study populations. He notes that although the investigators attempted to create a more diverse cohort, this study ultimately included primarily white women with long-term disease. This is a common challenge across many studies of rheumatoid arthritis. “I think this is a question that really may be different across different cultural contexts,” he adds.

The instruments used to assess health-related quality of life may account for some of the differences in these findings. For example, he points out that the HAQ (Health Assessment Questionnaire) is not as good at picking out changes in patients with relatively high levels of functionality. Differences in statistical methods (e.g., univariate vs. multivariate analyses) may also make a difference in the particular factors that statistically emerge. The phrasing of the patient global assessment can also influence results.

Dr. Craig sees the findings as somewhat reassuring, in that the patient global assessment correlated fairly well with active flare status. “It seems to be measuring primarily how the patient is actually functioning in their daily life,” he says. This “functionality” factor may be driven by a variety of different underlying causes. Some of these may be directly linked to current disease activity, but some may have other origins.

Based on these findings, Dr. Craig cautions against immediately ascribing an unexpectedly high patient global assessment to depression, although that may play a role for some people. “Our findings show that this situation of an unexpectedly high patient global assessment may provide a good opportunity to discuss the impact of RA symptoms on the patient’s functioning in daily life and their expectations of roles and activities,” he says. “It may give us a chance to better tailor our interventions.” For example, a patient with fatigue may benefit from physical therapy to combat deconditioning.

We may ultimately determine that definitions of remission that do not include the patient global assessment may be more helpful in tailoring immunosuppressive treatment. But regardless, the patient global assessment still carries important information for clinicians. Says Dr. Craig, “I think it serves as an approach to start the conversation. What is driving this particular measure?”