title: Rasch analysis of the Patient and Observer Scar Assessment Scale (POSAS) in burn scars.
abstract: OBJECTIVE
  The Patient and Observer Scar Assessment Scale (POSAS) is a questionnaire that was developed to assess scar quality. It consists of two separate six-item scales (Observer Scale and Patient Scale), both of which are scored on a 10-point rating scale. After many years of experience with this scale in burn scar assessment, it is appropriate to examine its psychometric properties using Rasch analysis.
  
  
  METHODS
  Cross-sectional data collection from seven clinical trials resulted in a data set of 1,629 observer scores and 1,427 patient scores of burn scars. We examined the person-item map, item fit statistics, reliability, response category ordering, and dimensionality of the POSAS.
  
  
  RESULTS
  The POSAS showed an adequate fit to the Rasch model, except for the item surface area. Person reliability of the Observer Scale and Patient Scale was 0.82 and 0.77, respectively. Dimensionality analysis revealed that the unexplained variance by the first contrast of both scales was 1.7 units. Spearman correlation between the Observer Scale Rasch measure and the overall opinion of the clinician was 0.75.
  
  
  CONCLUSIONS
  The Rasch model demonstrated that the POSAS is a reliable and valid scale that measures the single-construct scar quality.
authors: Association of Dutch Burn Centers, Beverwijk, The Netherlands.
authors: Martijn B A
authors: MB
authors: van der Wal
authors: Wim E
authors: WE
authors: Tuinebreijer
authors: Monica C T
authors: MC
authors: Bloemen
authors: Pauline D H M
authors: PD
authors: Verhaegen
authors: Esther
authors: E
authors: Middelkoop
authors: Paul P M
authors: PP
authors: van Zuijlen
references: Int J Low Extrem Wounds. 2007 Dec;6(4):249-53
references: 18048870
references: Plast Reconstr Surg. 2002 Mar;109(3):1108-22
references: 11884845
references: Qual Life Res. 2010 Aug;19(6):907-17
references: 20454864
references: Plast Reconstr Surg. 2005 Aug;116(2):514-22
references: 16079683
references: Qual Life Res. 2010 Sep;19(7):1057-68
references: 20419502
references: Plast Reconstr Surg. 2008 Apr;121(4):1421-1429
references: 18349665
references: Burns. 2011 Feb;37(1):74-81
references: 20510521
references: Plast Reconstr Surg. 2007 Feb;119(2):487-94
references: 17230080
references: Am J Clin Dermatol. 2003;4(4):245-72
references: 12680803
references: Plast Reconstr Surg. 2010 Aug;126(2):524-531
references: 20679835
references: J Craniofac Surg. 2010 May;21(3):719-23
references: 20485035
references: Am J Obstet Gynecol. 2010 Jul;203(1):36.e1-8
references: 20417924
references: J Plast Reconstr Aesthet Surg. 2009 Jun;62(6):713-20
references: 19303834
references: Plast Reconstr Surg. 2004 Jun;113(7):1960-5; discussion 1966-7
references: 15253184
references: Skin Res Technol. 2009 Feb;15(1):1-5
references: 19152571
references: J Wound Care. 2008 Mar;17(3):101-2, 104-6
references: 18376650
references: Health Qual Life Outcomes. 2009 Jun 22;7:58
references: 19545445
references: Arch Otolaryngol Head Neck Surg. 2008 Jan;134(1):85-93
references: 18209143
references: Qual Life Res. 2008 May;17(4):541-8
references: 18415705
references: J Plast Reconstr Aesthet Surg. 2009 Feb;62(2):216-20
references: 18054301
references: Burns. 2009 Aug;35(5):618-41
references: 19111399
references: J Clin Epidemiol. 2008 Dec;61(12):1289-1295
references: 18619791
references: Qual Life Res. 2009 May;18(4):473-81
references: 19238585
references: Qual Life Res. 2008 Nov;17(9):1183-93
references: 18825509
references: J Outcome Meas. 1999;3(2):103-22
references: 10204322
references: Burns. 2006 Feb;32(1):1-9
references: 16376020
references: Burns. 2010 Dec;36(8):1157-64
references: 20488623
references: Otolaryngol Head Neck Surg. 2007 Dec;137(6):868-72
references: 18036412