Skip to main content
SpringerLink
Log in

Differential item functioning in the Observer Scale of the POSAS for different scar types

  • Published:
Quality of Life Research Aims and scope Submit manuscript

Abstract

Purpose

To investigate whether the Observer Scale of the Patient and Observer Scar Assessment Scale (POSAS) can serve as a generic measure for scar quality across different scar types.

Methods

A collection of POSAS scores derived from several clinical trials on burn (n = 404), linear (n = 384), and keloidal scars (n = 282) was analyzed using the partial credit model of the Rasch analysis package RUMM2030.

Results

Differential item functioning (DIF) was observed for the Observer Scale of the POSAS between the three scar types for the items pliability, thickness, and surface area, which could be solved by item splitting. The items pigmentation and thickness showed disordered thresholds, considerable misfit, and unpredictability.

Conclusion

Users of the Observer Scale of the POSAS must be aware that the raw scores obtained from burn, linear, and keloidal scars cannot be compared without the scar-specific DIF adjustment of the items pliability, thickness, and surface area.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2

Similar content being viewed by others

References

  1. Baur, K. M., Hardy, P. E., & Van Dorsten, B. (1998). Posttraumatic stress disorder in burn populations: A critical review of the literature. Journal of Burn Care and Rehabilitation, 19(3), 230–240.

    Article  CAS  PubMed  Google Scholar 

  2. Rumsey, N., Clarke, A., & White, P. (2003). Exploring the psychosocial concerns of outpatients with disfiguring conditions. Journal of Wound Care, 12(7), 247–252.

    Article  CAS  PubMed  Google Scholar 

  3. Van Loey, N. E., & Van Son, M. J. (2003). Psychopathology and psychological problems in patients with burn scars: Epidemiology and management. American Journal of Clinical Dermatology, 4(4), 245–272.

    Article  PubMed  Google Scholar 

  4. van der Wal, M. B., Verhaegen, P. D., Middelkoop, E., & van Zuijlen, P. P. (2012). A clinimetric overview of scar assessment scales. Journal of Burn Care Res, 33(2), e79–e87.

    Article  Google Scholar 

  5. Verhaegen, P. D., van der Wal, M. B., Middelkoop, E., & van Zuijlen, P. P. (2011). Objective scar assessment tools: A clinimetric appraisal. Plastic and Reconstructive Surgery, 127(4), 1561–1570.

    Article  CAS  PubMed  Google Scholar 

  6. van Zuijlen, P. P., Angeles, A. P., Kreis, R. W., Bos, K. E., & Middelkoop, E. (2002). Scar assessment tools: Implications for current research. Plastic and Reconstructive Surgery, 109(3), 1108–1122.

    Article  PubMed  Google Scholar 

  7. Sullivan, T., Smith, J., Kermode, J., McIver, E., & Courtemanche, D. J. (1990). Rating the burn scar. Journal of Burn Care and Rehabilitation, 11(3), 256–260.

    Article  CAS  PubMed  Google Scholar 

  8. Baryza, M. J., & Baryza, G. A. (1995). The Vancouver Scar Scale: An administration tool and its interrater reliability. Journal of Burn Care and Rehabilitation, 16(5), 535–538.

    Article  CAS  PubMed  Google Scholar 

  9. Draaijers, L. J., Tempelman, F. R., Botman, Y. A., Tuinebreijer, W. E., Middelkoop, E., Kreis, R. W., et al. (2004). The Patient and Observer Scar Assessment Scale: A reliable and feasible tool for scar evaluation. Plastic and Reconstructive Surgery, 113(7), 1960–1965.

    Article  PubMed  Google Scholar 

  10. van de Kar, A. L., Corion, L. U., Smeulders, M. J., Draaijers, L. J., van der Horst, C. M., & van Zuijlen, P. P. (2005). Reliable and feasible evaluation of linear scars by the Patient and Observer Scar Assessment Scale. Plastic and Reconstructive Surgery, 116(2), 514–522.

    Article  PubMed  Google Scholar 

  11. O’Connell, D. A., Diamond, C., Seikaly, H., & Harris, J. R. (2008). Objective and subjective scar aesthetics in minimal access vs conventional access parathyroidectomy and thyroidectomy surgical procedures: A paired cohort study. Archives of Otolaryngology: Head and Neck Surgery, 134(1), 85–93.

    Article  Google Scholar 

  12. Cromi, A., Ghezzi, F., Gottardi, A., Cherubino, M., Uccella, S., & Valdatta, L. (2010). Cosmetic outcomes of various skin closure methods following cesarean delivery: A randomized trial. American Journal of Obstetrics and Gynecology, 203(1), 36e31–36e38.

    Article  Google Scholar 

  13. Bianchi, F. A., Roccia, F., Fiorini, P., & Berrone, S. (2010). Use of Patient and Observer Scar Assessment Scale for evaluation of facial scars treated with self-drying silicone gel. Journal of Craniofacial Surgery, 21(3), 719–723.

    Article  PubMed  Google Scholar 

  14. van der Wal, M. B., van Zuijlen, P. P., van de Ven, P., & Middelkoop, E. (2010). Topical silicone gel versus placebo in promoting the maturation of burn scars: A randomized controlled trial. Plastic and Reconstructive Surgery, 126(2), 524–531.

    Article  PubMed  Google Scholar 

  15. van der Wal, M. B., Tuinebreijer, W. E., Bloemen, M. C., Verhaegen, P. D., Middelkoop, E., & van Zuijlen, P. P. (2012). Rasch analysis of the Patient and Observer Scar Assessment Scale (POSAS) in burn scars. Quality of Life Research, 21(1), 13–23.

    Article  PubMed Central  PubMed  Google Scholar 

  16. Peacock, E. E, Jr, Madden, J. W., & Trier, W. C. (1970). Biologic basis for the treatment of keloids and hypertrophic scars. Southern Medical Journal, 63(7), 755–760.

    Article  PubMed  Google Scholar 

  17. Niessen, F. B., Spauwen, P. H., Schalkwijk, J., & Kon, M. (1999). On the nature of hypertrophic scars and keloids: A review. Plastic and Reconstructive Surgery, 104(5), 1435–1458.

    Article  CAS  PubMed  Google Scholar 

  18. Muir, I. F. (1990). On the nature of keloid and hypertrophic scars. British Journal of Plastic Surgery, 43(1), 61–69.

    Article  CAS  PubMed  Google Scholar 

  19. Ehrlich, H. P., Desmouliere, A., Diegelmann, R. F., Cohen, I. K., Compton, C. C., Garner, W. L., et al. (1994). Morphological and immunochemical differences between keloid and hypertrophic scar. American Journal of Pathology, 145(1), 105–113.

    CAS  PubMed Central  PubMed  Google Scholar 

  20. van der Wal, M. B., Vloemans, J. F., Tuinebreijer, W. E., van de Ven, P., van Unen, E., van Zuijlen, P. P., et al. (2012). Outcome after burns: An observational study on burn scar maturation and predictors for severe scarring. Wound Repair and Regeneration, 20(5), 676–687.

    Article  PubMed  Google Scholar 

  21. Verhaegen, P. D., van Zuijlen, P. P., Pennings, N. M., van Marle, J., Niessen, F. B., van der Horst, C. M., et al. (2009). Differences in collagen architecture between keloid, hypertrophic scar, normotrophic scar, and normal skin: An objective histopathological analysis. Wound Repair and Regeneration, 17(5), 649–656.

    Article  PubMed  Google Scholar 

  22. Verhaegen, P. D., van der Wal, M. B., Bloemen, M. C., Dokter, J., Melis, P., Middelkoop, E., et al. (2011). Sustainable effect of skin stretching for burn scar excision: Long-term results of a multicenter randomized controlled trial. Burns, 37(7), 1222–1228.

    Article  PubMed  Google Scholar 

  23. Bloemen, M. C., van Gerven, M. S., van der Wal, M. B., Verhaegen, P. D., & Middelkoop, E. (2011). An objective device for measuring surface roughness of skin and scars. Journal of the American Academy of Dermatology, 64(4), 706–715.

    Article  PubMed  Google Scholar 

  24. van der Wal, M. B., Bloemen, M. C., Verhaegen, P. D., Tuinebreijer, W. E., de Vet, H. C., van Zuijlen, P. P., et al. (2013). Objective color measurements: clinimetric performance of three devices on normal skin and scar tissue J Burn Care Res, 34(3), 187–194.

    Google Scholar 

  25. Bloemen, M. C., van der Wal, M. B., Verhaegen, P. D., Nieuwenhuis, M. K., van Baar, M. E., van Zuijlen, P. P., et al. (2012). Clinical effectiveness of dermal substitution in burns by topical negative pressure: A multicenter randomized controlled trial. Wound Repair and Regeneration, 20(6), 797–805.

    Article  PubMed  Google Scholar 

  26. Linacre, J. M. (1994). Sample size and item calibration stability. Rasch Measurement Transactions, 7(4), 328.

    Google Scholar 

  27. Linacre, J. M. (2002). Optimizing rating scale category effectiveness. Journal of Applied Measurement, 3(1), 85–106.

    PubMed  Google Scholar 

  28. Tennant, A., & Conaghan, P. G. (2007). The Rasch measurement model in rheumatology: What is it and why use it? When should it be applied, and what should one look for in a Rasch paper? Arthritis and Rheumatism, 57(8), 1358–1362.

    Article  PubMed  Google Scholar 

  29. Fisher, W. P, Jr. (1992). Reliability statistics. Rasch Measurement Transactions, 6, 238.

    Google Scholar 

  30. Wright, B. D., & Masters, G. (2002). Number of person or item strata. Rasch Measurement Transactions, 16, 888.

    Google Scholar 

  31. Nunnaly, J. C. (1978). Psychometric Theory (2nd (edition ed.). New York: McGraw-Hill.

    Google Scholar 

  32. Bland, J. M., & Altman, D. G. (1995). Multiple significance tests: The Bonferroni method. BMJ, 310(6973), 170.

    Article  CAS  PubMed Central  PubMed  Google Scholar 

  33. Smith, E. V, Jr. (2002). Detecting and evaluating the impact of multidimensionality using item fit statistics and principal component analysis of residuals. Journal of Applied Measurement, 3(2), 205–231.

    PubMed  Google Scholar 

  34. Tennant, A., & Pallant, J. F. (2012). The root mean square error of approximation (RMSEA) as a supplementary statistic to determine fit to the Rasch model with large sample sizes. Rasch Measurement Transactions, 4, 1348–1349.

    Google Scholar 

  35. Wright, B. D. (1996). Local dependency, correlations and principal components. Rasch Measurement Transactions, 10, 509–511.

    Google Scholar 

  36. Wainer, H., & Kiely, G. (1987). Item clusters and computer adaptive testing: A case for testlets. Journal of Educational Measurement, 24(3), 185–201.

    Article  Google Scholar 

  37. Andrich, D., & Hagquist, C. (2011). Real and artificial differential item functioning. Journal of Educational and Behavioral Statistics, 37, 387–416.

    Article  Google Scholar 

  38. Bond, T. G., & Fox, C. M. (2007). Model Fit and Unidimensionality. In Applying the Rasch model. Fundamental measurement in the human sciences. Second Edition, (pp. 236–260).

  39. Lundgren-Nilsson, A., Grimby, G., Ring, H., Tesio, L., Lawton, G., Slade, A., et al. (2005). Cross-cultural validity of functional independence measure items in stroke: A study using Rasch analysis. Journal of Rehabilitation Medicine, 37(1), 23–31.

    Article  PubMed  Google Scholar 

  40. Cunningham, T. J., Berkman, L. F., Gortmaker, S. L., Kiefe, C. I., Jacobs, D. R, Jr, Seeman, T. E., et al. (2011). Assessment of differential item functioning in the experiences of discrimination index: The coronary artery risk development in young adults (CARDIA) Study. American Journal of Epidemiology, 174(11), 1266–1274.

    Article  PubMed Central  PubMed  Google Scholar 

  41. Lawton, G., Bhakta, B. B., Chamberlain, M. A., & Tennant, A. (2004). The Behcet’s disease activity index. Rheumatology (Oxford), 43(1), 73–78.

    Article  CAS  Google Scholar 

  42. Gothwal, V. K., Wright, T. A., Lamoureux, E. L., & Pesudovs, K. (2009). Rasch analysis of visual function and quality of life questionnaires. Optometry and Vision Science, 86(10), 1160–1168.

    Article  PubMed  Google Scholar 

  43. Gothwal, V. K., Wright, T., Lamoureux, E. L., & Pesudovs, K. (2010). Psychometric properties of visual functioning index using Rasch analysis. Acta Ophthalmologica, 88(7), 797–803.

    Article  PubMed  Google Scholar 

  44. Weisscher, N., Glas, C. A., Vermeulen, M., & De Haan, R. J. (2010). The use of an item response theory-based disability item bank across diseases: Accounting for differential item functioning. Journal of Clinical Epidemiology, 63(5), 543–549.

    Article  PubMed  Google Scholar 

  45. van Groen, M. M., ten Klooster, P. M., Taal, E., van de Laar, M. A., & Glas, C. A. (2010). Application of the health assessment questionnaire disability index to various rheumatic diseases. Quality of Life Research, 19(9), 1255–1263.

    Article  PubMed Central  PubMed  Google Scholar 

Download references

Acknowledgments

The authors would like to thank L.C. Langenberg and D. Wellenstein for their assistance in collecting the data.

Author information

Authors and Affiliations

  1. Association of Dutch Burn Centers, Beverwijk, The Netherlands

    Martijn B. A. van der Wal, Wim E. Tuinebreijer, Esther Middelkoop & Paul P. M. van Zuijlen

  2. Burn Center, Red Cross Hospital, Beverwijk, The Netherlands

    Martijn B. A. van der Wal, Esther Middelkoop & Paul P. M. van Zuijlen

  3. Department of Plastic, Reconstructive, and Hand Surgery, VU Medical Center, Amsterdam, The Netherlands

    Martijn B. A. van der Wal, Esther Middelkoop & Paul P. M. van Zuijlen

  4. Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden

    Åsa Lundgren-Nilsson

  5. Department of Plastic, Reconstructive, and Hand Surgery, Red Cross Hospital, Vondellaan 13, 1942 LE, Beverwijk, The Netherlands

    Paul P. M. van Zuijlen

Authors
  1. Martijn B. A. van der Wal
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Wim E. Tuinebreijer
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Åsa Lundgren-Nilsson
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Esther Middelkoop
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Paul P. M. van Zuijlen
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Martijn B. A. van der Wal.

Rights and permissions

Reprints and permissions

About this article

Cite this article

van der Wal, M.B.A., Tuinebreijer, W.E., Lundgren-Nilsson, Å. et al. Differential item functioning in the Observer Scale of the POSAS for different scar types. Qual Life Res 23, 2037–2045 (2014). https://doi.org/10.1007/s11136-014-0637-4

Download citation

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11136-014-0637-4

Keywords

Search

Navigation