Study: Patient Global Assessment Scores Give Insight Into Daily Function

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A recent article in Arthritis Care & Research supports the idea that the patient global assessment reflects primarily the patient’s experience of their functioning in daily life.¹

Background

The patient global assessment is a key measure used by clinicians and researchers to help evaluate disease status in rheuma­toid arthritis (RA). Lead author Ethan T. Craig, MD, MHS, an assistant professor of clinical medicine at the University of Pennsylvania, Philadelphia, and associate editor of The Rheumatologist, explains, “It’s there to capture a gestalt of the patient’s experience of how things are going.”

The patient global assessment is a component of many different disease activity scores used to assess treatment goals in RA, including the CDAI (Clinical Disease Activity Index), the RAPID3 (Routine Assessment of Patient Index Data) and the DAS28 (28-joint count Disease Activity Score).²

The patient global assessment is given as a single question, scored from 0–10 or 0–100, with higher numbers representing worse perceived disease activity or overall health. The non-standardized question can be phrased in terms of global health or overall disease activity.² “Depending on how you formulate that question,” notes Dr. Craig, “you may get different responses.”

One strength of the patient global assessment is that it provides a lot of basic information in one number. “But one of its limitations is assessing what exactly is being communicated to us,” says Dr. Craig. “When a patient tells me their score is 10 on a scale of 0–10, does that indicate they are having a lot of pain? Does that indicate they are not functioning well? Does it indicate they are very fatigued? It’s a key question: What aspects of experience are patients drawing on when they report a global assessment?”

Dr. Craig initially became interested in studying the patient global assessment to explore the question of discordance—when patients’ assessments don’t correspond with the rest of the data, as assessed by the clinician. “We know from previous studies that the patient global assessment is the most common parameter to impact attainment of remission in the Boolean-based remission criteria,” he says. Some researchers have even proposed removing the patient global assessment from these remission criteria and focusing on such data as swollen joint counts and C-reactive protein levels.³

Dr. Craig notes that pain has reliably been found to be associated with the patient global assessment. To some extent, physical function and fatigue have shown this association as well. “The piece that has been a little more controversial has been the role of anxiety and depression,” he says.

Although patient global assessment scores tend to track with physician-assessed measures of disease activity, some studies have indicated they are also associated with other components of health, such as mental health comorbidities. Dr. Craig adds, “I think there is a sense that when the patient global assessment doesn’t track well with physician assessments or with RA activity scores, that it may reflect anxiety or depression.”

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?”

Ruth Jessen Hickman, MD, is a graduate of the Indiana University School of Medicine. She is a freelance medical and science writer living in Bloomington, Ind.

References

1. Craig ET, Perin J, Zeger S, et al. What does the patient global health assessment in RA really tell us? Contribution of specific dimensions of health-related quality of life. Arthritis Care Res (Hoboken). 2020 Nov;72(11):1571–1578.
2. Nikiphorou E, Radner H, Chatzidionysiou K, et al. Patient global assessment in measuring disease activity in rheumatoid arthritis: A review of the literature. Arthritis Res Ther. 2016 Oct 28;18(1):251.
3. Ferreira RJO, Duarte C, Ndosi M, et al. Suppressing inflammation in rheumatoid arthritis: Does patient global assessment blur the target? A practice-based call for a paradigm change. Arthritis Care Res (Hoboken). 2018 Mar;70(3):369–378.