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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. [ABSTRACT FROM AUTHOR]

Long-term outcome of burn scars as well as the relation with clinically relevant parameters has not been studied quantitatively. Therefore, we conducted a detailed analysis on the clinical changes of burn scars in a longitudinal setup. In addition, we focused on the differences in scar quality in relation to the depth, etiology of the burn wound and age of the patient. Burn scars of 474 patients were subjected to a scar assessment protocol 3, 6, and 12 months postburn. Three different age groups were defined (≤5, 5-18, and ≥18 years). The observer part of the Patient and Observer Scar Assessment Scale revealed a significant ( p < 0.001) improvement in scar quality at 12 months compared with the 3- and 6-month data. Predictors for severe scarring are depth of the wound ( p < 0.001) and total body surface area burned ( p < 0.001). Etiology ( p = 0.753) and age ( p > 0.230) have no significant influence on scar quality when corrected for sex, total body surface area burned, time, and age or etiology, respectively. [ABSTRACT FROM AUTHOR]

Purpose: 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. Conclusion: The Rasch model demonstrated that the POSAS is a reliable and valid scale that measures the single-construct scar quality. [ABSTRACT FROM AUTHOR]