Interpretation and precision of the Observer Scar Assessment Scale improved by a revised scoring.
OBJECTIVE
To apply Rasch measurement to develop a rule for clinical interpretation of the Observer Scar Assessment Scale (OSAS) to help surgeons judge reported sum scores clinically.


METHODS
We used cross-sectional data of a multicenter randomized clinical trial for the treatment of nontuberculous cervicofacial lymphadenitis in children. Rasch analysis was used on the OSAS scores obtained from scar photographs of 100 children after surgical or antibiotic treatment.


RESULTS
Rasch analysis showed that all OSAS item rating scales needed revision and weighting. After doing so, raw scale scores could be converted into quantitative interval scale-based measures of scar quality. The clinical interpretation of the OSAS was clearly improved by the revised scoring. By using the Rasch-modeled item and person measures, the most likely OSAS score patterns associated with the revised OSAS sum scores could be determined.


CONCLUSIONS
The Rasch analysis improved the measurement properties and clinical interpretability of the OSAS instrument.
Lindeboom
Jerome A
JA
Department of Oral and Maxillofacial Surgery, Academic Medical Center, Amsterdam, The Netherlands; Academic Center for Dentistry (ACTA), University of Amsterdam, Amsterdam, The Netherlands. Electronic address: j.a.lindeboom@amc.uva.nl.
Bruijnesteijn van Coppenraet
Elisabeth S
ES
Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
Kuijper
Ed J
EJ
Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
Polsbroek
Roger M
RM
Department of Oral and Maxillofacial Surgery, Academic Medical Center, Amsterdam, The Netherlands; Academic Center for Dentistry (ACTA), University of Amsterdam, Amsterdam, The Netherlands.
Horsthuis
Roy B
RB
Department of Oral and Maxillofacial Surgery, Academic Medical Center, Amsterdam, The Netherlands; Academic Center for Dentistry (ACTA), University of Amsterdam, Amsterdam, The Netherlands.
Prins
Jan M
JM
Department of Internal Medicine, Division of Infectious Diseases, Tropical Medicine and AIDS, Amsterdam, The Netherlands; Center of Infection and Immunity Amsterdam (CINIMA), Amsterdam, The Netherlands.
Lindeboom
Robert
R
Department of Clinical Epidemiology, Biostatistics, and Bioinformatics, Academic Medical Center, Amsterdam, The Netherlands.
D000293:Adolescent; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D002921:Cicatrix / Q000473:pathology* / Q000503:physiopathology; D004548:Elasticity; D004812:Epidemiologic Methods; D004954:Esthetics; D005145:Face / Q000601:surgery; D006801:Humans; D007223:Infant; D008199:Lymphadenitis / Q000188:drug therapy / Q000601:surgery*; D009333:Neck / Q000601:surgery; D010781:Photography; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply; D012880:Skin Pigmentation; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents