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.

References

•Copay AG, Subach BR, Glassman SD, Polly DW, Schuler TC. Understanding the minimum clinically important difference: a review of concepts and methods. The Spine Journal 2007;7:541–546.
•Harvill LM. An NCME Instructional Module on. Standard Error of Measurement. Educational Measurement: Issues and Practice 1991;10:33–41.
•Mouelhi Y, Jouve E, Castelli C, Gentile S. How is the minimal clinically important difference established in health-related quality of life instruments? Review of anchors and methods. Health Qual Life Outcomes 2020;18:136.
•Revicki D, Hays RD, Cella D, Sloan J. Recommended methods for determining responsiveness and minimally important differences for patient-reported outcomes. J Clin Epidemiol 2008;61:102–109.
•Nunnally JC. Psychometric theory. New York …: McGraw-Hill, 1967.
•Turk DC, Dworkin RH, Allen RR, Bellamy N, Brandenburg N, Carr DB, Cleeland C, Dionne R, Farrar JT, Galer BS, Hewitt DJ, Jadad AR, Katz NP, Kramer LD, Manning DC, McCormick CG, McDermott MP, McGrath P, Quessy S, Rappaport BA, Robinson JP, Royal MA, Simon L, Stauffer JW, Stein W, Tollett J, Witter J. Core outcome domains for chronic pain clinical trials: IMMPACT recommendations. Pain 2003;106:337–345.
•Kaiser U, Kopkow C, Deckert S, Neustadt K, Jacobi L, Cameron P, De Angelis V, Apfelbacher C, Arnold B, Birch J, Bjarnegård A, Christiansen S, C de C Williams A, Gossrau G, Heinks A, Hüppe M, Kiers H, Kleinert U, Martelletti P, McCracken L, de Meij N, Nagel B, Nijs J, Norda H, Singh JA, Spengler E, Terwee CB, Tugwell P, Vlaeyen JWS, Wandrey H, Neugebauer E, Sabatowski R, Schmitt J. Developing a core outcome domain set to assessing effectiveness of interdisciplinary multimodal pain therapy: the VAPAIN consensus statement on core outcome domains. Pain 2018;159:673–683.
•Wyrwich KW, Bullinger M, Aaronson N, Hays RD, Patrick DL, Symonds T. Estimating clinically significant differences in quality of life outcomes. Quality of Life Research 2005;14:285–295.

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