title: Discriminant validity, responsiveness and reliability of the arthritis-specific Work Productivity Survey assessing workplace and household productivity within and outside the home in patients with axial spondyloarthritis, including nonradiographic axial spondyloarthritis and ankylosing spondylitis.
abstract: BACKGROUND
  The arthritis-specific Work Productivity Survey (WPS) was developed to evaluate productivity limitations associated with arthritis within and outside the home. There is an unmet need for an instrument assessing similar productivity limitations in axial spondyloarthritis (axSpA), including nonradiographic axSpA and ankylosing spondylitis. Following its validation in rheumatoid and psoriatic arthritis, we aimed to assess psychometric properties of WPS in adult-onset active axSpA in this analysis.
  
  
  METHODS
  Psychometric properties were assessed using data from the RAPID-axSpA trial (NCT01087762) in which researchers investigated certolizumab pegol efficacy and safety in axSpA. WPS was completed at baseline and every 4 weeks until week 24. Validity was evaluated at study baseline via known-groups defined by the first and third quartile cutoffs of patient scores to Ankylosing Spondylitis Disease Activity Score (ASDAS), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), back pain, Bath Ankylosing Spondylitis Functional Index (BASFI), Short Form 36 health survey (SF-36) and Ankylosing Spondylitis Quality of Life Scale (ASQoL). Responsiveness and reliability were assessed by comparing WPS mean changes in ASAS 20% improvement criteria (ASAS20), BASDAI50, ASDAS clinically important improvement/major improvement (CII/MI) and BASFI minimum clinically important difference (MCID) responders versus nonresponders at week 12. All comparisons were conducted on observed cases in the randomized set using a nonparametric bootstrap-t method.
  
  
  RESULTS
  The results confirmed the psychometric properties of WPS. AxSpA patients with a worse health state had significantly more days of household work lost, household work with reduced productivity, social activities missed and outside help hired, as well as a higher interference rate of arthritis, than patients with a better health state. Similarly, employed patients with a worse health state had significantly more work days lost or with productivity reduced, and a higher interference of arthritis on work productivity. Similar findings were also observed in the nonradiographic (nr) axSpA and AS subpopulations. The WPS was responsive to clinical changes, with responders reporting larger improvements at week 12 in WPS scores versus nonresponders. Effect sizes in responders were generally moderate to large (standardized response mean >0.5).
  
  
  CONCLUSIONS
  These analyses demonstrate that WPS is a valid, responsive and reliable instrument for the measurement of productivity within and outside the home in adult-onset axSpA, as well as the in subpopulations of AS and nr-axSpA.
authors.affiliation: Wasatch Health Outcomes, 2613 Silver Cloud Drive, Park City, UT, 84060, USA. jtosterhaus@mindspring.com.
authors.forename: Jane T
authors.initials: JT
authors.lastname: Osterhaus
authors.affiliation: UCB Pharma, Allee de la Recherche, 60, 1070, Brussels, Belgium. Oana.Purcaru@ucb.com.
authors.forename: Oana
authors.initials: O
authors.lastname: Purcaru
mesh_terms: D000328:Adult; D000068582:Certolizumab Pegol / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000627:therapeutic use; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D025241:Spondylarthritis / Q000188:drug therapy* / Q000523:psychology; D013167:Spondylitis, Ankylosing / Q000188:drug therapy* / Q000523:psychology; D017132:Workplace
chemical_list: D007140:Immunoglobulin Fab Fragments; D007166:Immunosuppressive Agents; D000068582:Certolizumab Pegol
references.citation: Ann Rheum Dis. 1985 Jun;44(6):359-67
references.pmid: 3160312
references.citation: J Rheumatol. 1999 Aug;26(8):1752-6
references.pmid: 10451073
references.citation: Rheumatol Int. 2003 Mar;23(2):61-6
references.pmid: 12634937
references.citation: J Rheumatol. 2009 Sep;36(9):2100-9
references.pmid: 19738221
references.citation: Pharmacoeconomics. 2004;22(4):225-44
references.pmid: 14974873
references.citation: Arthritis Res Ther. 2009;11(3):R73
references.pmid: 19457255
references.citation: Med Care. 1992 Jun;30(6):473-83
references.pmid: 1593914
references.citation: Ann Rheum Dis. 2010 Jun;69(6):1123-8
references.pmid: 20439293
references.citation: Arthritis Rheum. 1992 May;35(5):498-502
references.pmid: 1575785
references.citation: Ann Rheum Dis. 2009 Dec;68(12):1811-8
references.pmid: 19060001
references.citation: Am J Manag Care. 2007 Apr;13(4):211-7
references.pmid: 17408341
references.citation: J Rheumatol. 2005 Jan;32(1):80-5
references.pmid: 15630730
references.citation: Clin Exp Rheumatol. 2009 Jul-Aug;27(4 Suppl 55):S118-23
references.pmid: 19822057
references.citation: Scand J Rheumatol. 2005 Mar-Apr;34(2):97-108
references.pmid: 16095004
references.citation: Rheumatology (Oxford). 2010 Apr;49(4):812-9
references.pmid: 20100797
references.citation: J Rheumatol. 2005 Nov;32(11):2250-6
references.pmid: 16265712
references.citation: Arthritis Rheum. 2009 Nov 15;61(11):1592-600
references.pmid: 19877104
references.citation: Stat Med. 2000 Dec 15;19(23):3219-36
references.pmid: 11113956
references.citation: Ann Rheum Dis. 2009 Jun;68(6):770-6
references.pmid: 19297345
references.citation: J Rheumatol. 2007 Nov;34(11):2273-84
references.pmid: 17896800
references.citation: Arthritis Res Ther. 2014 Jul 04;16(4):R140
references.pmid: 24996416
references.citation: J Rheumatol. 1994 Dec;21(12):2281-5
references.pmid: 7699629
references.citation: Ann Rheum Dis. 2005 Nov;64 Suppl 4:iv65-9
references.pmid: 16239392
references.citation: Arthritis Rheum. 2001 Aug;44(8):1876-86
references.pmid: 11508441
references.citation: Arthritis Rheum. 2009 Mar;60(3):717-27
references.pmid: 19248087
references.citation: Ann Rheum Dis. 2003 Jan;62(1):20-6
references.pmid: 12480664
references.citation: Rheumatology (Oxford). 2010 Oct;49(10):1900-10
references.pmid: 20547658
references.citation: Arthritis Rheum. 1984 Apr;27(4):361-8
references.pmid: 6231933
references.citation: Arthritis Rheum. 2005 Feb 15;53(1):5-11
references.pmid: 15696569
references.citation: J Rheumatol. 2011 Aug;38(8):1776-90
references.pmid: 21807801
references.citation: J Rheumatol. 2003 Apr;30(4):764-73
references.pmid: 12672197
references.citation: J Rheumatol. 2003 Apr;30(4):868-72
references.pmid: 12672218
references.citation: Arthritis Rheum. 1993 Jun;36(6):729-40
references.pmid: 8507213
references.citation: J Rheumatol. 2007 Jun;34(6):1372-80
references.pmid: 17552063
references.citation: Arthritis Care Res (Hoboken). 2012 Jun;64(6):905-10
references.pmid: 22275150
references.citation: Ann Rheum Dis. 2014 Jan;73(1):39-47
references.pmid: 24013647
references.citation: Pharmacoeconomics. 2004;22(3):165-84
references.pmid: 14871164
references.citation: J Rheumatol. 2001 May;28(5):1056-62
references.pmid: 11361189