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Psoriatic arthritis
Original article
Fatigue numeric rating scale validity, discrimination and responder definition in patients with psoriatic arthritis
  1. Dafna Gladman1,
  2. Peter Nash2,
  3. Hitoshi Goto3,
  4. Julie A Birt4,
  5. Chen-Yen Lin4,
  6. Ana-Maria Orbai5 and
  7. Tore K Kvien6
  1. 1 Medicine/Rheumatology, Krembil Research Institute, Toronto, Ontario, Canada
  2. 2 Department of Medicine, Griffith University, Brisbane, Queensland, Australia
  3. 3 Osaka City University Hospital, Osaka, Japan
  4. 4 Eli Lilly and Company, Indianapolis, Indiana, USA
  5. 5 Medicine Rheumatology, Johns Hopkisn University, Baltimore, Maryland, USA
  6. 6 Rheumatology, Diak Hospital, Oslo, Norway
  1. Correspondence to Dr Dafna Gladman; dafna.gladman{at}utoronto.ca

Abstract

Objectives This study assessed the psychometric properties of the fatigue numeric rating scale (NRS) and sought to establish values for clinically meaningful change (responder definition).

Methods Using disease-specific clinician-reported and patient-reported data from two randomised clinical trials of patients with psoriatic arthritis (PsA), the fatigue NRS was evaluated for test–retest reliability, construct validity and responsiveness. A responder definition was also explored using anchor-based and distribution-based methods.

Results Test–retest reliability analyses supported the reproducibility of the fatigue NRS in patients with PsA (intraclass correlation coefficient=0.829). Mean (SD) values at baseline and week 2 were 5.7 (2.2) and 5.7 (2.4), respectively. Supporting construct validity of the fatigue NRS, moderate-to-large correlations with other assessments measuring similar concepts as measured by Sackett’s conventions were demonstrated. Fatigue severity was reduced when the underlying disease activity was improved and reductions remained consistent at week 12 and 24. A 3-point improvement was identified as being optimal for demonstrating a level of clinically meaningful improvement in fatigue NRS after 12–24 weeks of treatment.

Conclusions Fatigue NRS is a valid and responsive patient-reported outcome instrument for use in patients with PsA. The established psychometric properties from this study support the use of fatigue NRS in clinical trials and in routine clinical practice. Robust validation of reliability for use in routine clinical practice in treating patients with active PsA in less active disease states and other more diverse ethnic groups is needed.

  • psoriatic arthritis
  • patient perspective
  • outcomes research
http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/rmdopen-2019-000928

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    Footnotes

    • Contributors All authors have made substantial contributions to the conception or design of the work, or the acquisition, analysis or interpretation of data, have drafted the work or revised it critically for important intellectual content and have provided final approval of the manuscript.

    • Funding This work was supported by Eli Lilly and Company.

    • Competing interests DG received research grant support and/or consulting fees from Abbvie, Amgen, BMS, Celgene, Eli Lilly and Company, Janssen, Novartis, Pfizer and UCB. PN has received grants for research and for clinical trials and honoraria for advice and lectures from AbbVie, Amgen, BMS, Celgene, Eli Lilly and Company, Janssen, MSD, Novartis, Pfizer, Roche, Sanofi and UCB. HG has received fees for speaking and/or consulting from Abbie, Asahi Kasei, Astellas, Chugai, Eisai, Eli Lilly and Company, Janssen, Mitsubishi Tanabe, Ono, Pfizer, Santen, Takeda, and received research funding to Osaka City General Hospital from AbbVie, Chugai, Eisai, Eli Lilly and Company, Janssen, Sanofi and Santen. A-MO received research grant support and/or consulting fees from Celgene, Eli Lilly and Company, Horizon, Janssen, Novartis, Pfizer and UCB. TKK has received fees for speaking and/or consulting from AbbVie, Biogen, BMS, Boehringer Ingelheim, Celgene, Celltrion, Eli Lilly and Company, Epirus, Hospira, Merck-Serono, MSD, Mundipharma, Novartis, Oktal, Orion Pharma, Hospira/Pfizer, Roche, Sandoz, and UCB and received research funding to Diakonhjemmet Hospital from AbbVie, BMS, MSD, Pfizer, Roche and UCB. JB and C-YL are full-time employees of and hold stock/stock options in Eli Lilly and Company.

    • Patient consent for publication Not required.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.