Background & Aims
In pain research many recommended outcome measures are patient-reported instruments. To interpret such measurements we need to know the size of the measurement error and to understand what can be considered an important outcome change. In the study presented, standard error of measurement (SEM), minimal detectable change (MDC) and minimal clinically important difference (MCID) were estimated for the commonly used Short Form-36 Health Survey (SF-36) physical and mental component summaries (PCS and MCS subscales), Hospital Anxiety and Depression Scale anxiety (HADS-A) and depression (HADS-D) and Numeric Rating Scale (NRS) for pain intensity during the past week.
Methods
Estimates were based on data from the Swedish Quality Registry for Pain Rehabilitation in a sample of patients with chronic pain undergoing interdisciplinary pain rehabilitation programs (n=8854). They were calculated both in the total sample and for subgroups with pain-related diagnoses. MCID was estimated as average change and change difference. Three anchors were used: 1) “How would you judge your general health today as compared to one year ago?”, 2) “Has your rehabilitation period changed your experience of pain?”, and 3) “Has your rehabilitation period changed your ability to manage your life situation overall?” Anchor 1 was the health transition item from the SF-36 and anchors 2 and 3 were based on questions available in the registry.
Results
Our analysis contributed with estimates of MCID for SF-36 PCS, ranging between 2.62-4.69, for SF-36 MCS between 4.46-6.79, for NRS between 0.895-1.48, for HADS-A between 1.17-2.13, and for HADS-D between 1.48-2.54. We also found that the common assumption that SEM for pre- and post-treatment measurements are the same is not universally applicable.
Conclusions
The provided estimates of MCID and MDC can be used in future research as threshold values for when a change can be considered large enough to be of subjective importance to an individual (in the case of MCID) and to not be attributable to measurement error (in the case of MDC). The use of several anchors allows for the selection of an MCID related to the health aspect of interest. When utilizing MCID researchers should carefully consider selecting an appropriate estimation method and anchor that aligns with the specific characteristics and objectives of the study.
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Presenting Author
Rode Grönkvist
Poster Authors
Rode Grönkvist, MSc
MSc
Inst of Medicine, Sahlgrenska Academy, Gothenburg University
Lead Author
Linda Vixner
PhD
University of Dalarna
Lead Author
Björn Äng
Dalarna University
Lead Author
Anna Grimby
School of Public Health and Community Medicine, Department of Med., Gothenburg Univ
Lead Author
Topics
- Assessment and Diagnosis