Original Article
Domain-specific transition questions demonstrated higher validity than global transition questions as anchors for clinically important improvement

https://doi.org/10.1016/j.jclinepi.2015.01.028Get rights and content

Abstract

Objectives

Estimates of minimal clinically important differences in health measures may be affected by the anchor used. We examined if domain-specific transition questions had higher construct validity than global health transition questions as anchors for measures in a given domain.

Study Design and Setting

In a prospective study of 249 patients with rheumatoid arthritis, we examined changes in pain, physical function, joint swelling, stiffness, fatigue, and depression with treatment. We related these changes to a domain-specific transition question, global arthritis transition question, and the Short Form-36 (SF-36) health transition item.

Results

Changes in all six clinical measures were more highly correlated with the domain-specific transition questions than with the global arthritis question and SF-36 transition question. Discrimination between patients who improved or not was also better using domain-specific questions. Estimates of minimal clinically important improvement (MCII) differed with the anchor when these were based on mean changes. MCII estimates from receiver operating characteristic curve analysis were not influenced by the choice of anchor when anchors had high agreement.

Conclusion

Domain-specific transition questions had higher construct validity as anchors for determining clinically important differences in health measures focused on a single domain than either global disease or general health transition questions.

Introduction

What is new?

  • This is the first study to test whether domain-specific transition questions have higher validity as anchors for estimating clinically important differences than global transition questions.

  • Domain-specific transition questions were more highly correlated with changes in clinical measures than either a global disease transition question or the health transition item of the Short Form-36 and had better discrimination.

  • Domain-specific transition questions should be used as anchors for clinical measures focused on a specific domain.

Interpretation of changes in health status measures and other patient-reported outcomes is aided by knowing the amount of change that is considered meaningful or important [1]. Distribution-based methods and anchor-based methods are the two approaches commonly used to estimate clinically important differences [2]. Anchor-based methods relate the change in the measure to an external standard (i.e., anchor) that indicates whether a recognizable change in status has occurred. These anchors may be clinical, such as reduced use of analgesics as the anchor for measures of pain severity, or the anchor may be physician or patient judgments. Patient judgments are not only convenient but may also be the most relevant. These anchors are often single-item transition questions that ask the patient to assess if his or her health has improved, worsened, or remained unchanged over some time and usually also include an estimate of the importance of any change [3].

Diseases often impact several health domains. For example, benign prostatic hypertrophy affects not only urinary symptoms but also sleep and fatigue, and chronic arthritis commonly affects pain, physical functioning, stiffness, and work ability. To assess health among patients with these conditions comprehensively, several domain-specific measures are often used because their specificity tends to make them more responsive than global health measures [4]. In choosing anchors to estimate clinically important differences in multiple domains, investigators must decide whether to use a series of domain-specific transition questions (e.g., Has your pain changed? Has your sleep changed?) or to apply the response to a single global transition question (e.g., Has your health changed?) to all domain measures. Domain-specific transition questions are more targeted and would therefore presumably elicit judgments that were more closely linked to changes in the clinical measure [5], [6], [7], [8], [9]. However, using multiple domain-specific transition questions increases respondent burden, and a global transition question may adequately substitute, particularly if all domains are expected to respond similarly to treatment. Some investigators have used study-specific global transition questions [10], [11], [12], whereas others have used the health transition question of the Short Form-36 (SF-36) as the anchor, often when no other transition questions were included [13], [14], [15].

The relative validity of domain-specific transition questions and global health transition questions has not previously been examined. We compared the construct validity of six domain-specific transition questions, one global disease transition question, and the SF-36 health transition question as anchors in a study of clinically important changes in patients with active rheumatoid arthritis (RA).

Section snippets

Subjects

We enrolled subjects with active RA in a prospective longitudinal study to determine estimates of minimal clinically important improvement (MCII) for measures of RA activity [16]. Eligible subjects were adults with RA seen in our clinics who had at least six tender joints and who in the judgment of their rheumatologist required an escalation in treatment with either disease-modifying medications or prednisone. The study protocol was approved by the institutional review board, and all subjects

Results

Of 250 subjects enrolled, we included 249 subjects who completed the SF-36 health transition item at the second visit. Their mean (±standard deviation) age was 50.9 ± 13.7 years, and median duration of RA was 6.2 years; 78% were women.

On the domain-specific transition questions, improvement was reported by 65% of subjects for pain, 61% for ability to do things, 63% for joint swelling, 58% for stiffness, 47% for fatigue, and 49% for depression. Improvement on the global arthritis transition

Discussion

Domain-specific transition questions in this study demonstrated higher correlations with changes in clinical measures, as well as better discrimination in ROC curve analysis, than either a global arthritis transition question or the health transition item of the SF-36. Although there were only marginal differences in ROC curve areas between the domain-specific transition questions and the global arthritis transition question, the correlations with clinical changes were notably higher for each

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    Funding: This study was supported by the Intramural Research Program, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health grant ZIA AR041153 and U.S. Public Health Service grant AR45177.

    Conflict of Interest: None.

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