Development of the Observer Scales of the Patient and Observer Scar Assessment Scale: An International Delphi Study

Background: This Delphi study aimed to develop the Observer Scale of the Patient and Observer Scar Assessment Scale (POSAS) 3.0 for measurements of scar quality in patients with all types of scars. The POSAS 3.0 Patient Scale has been developed using an extensive qualitative study, which has been published separately. Methods: An online, 3-round Delphi study was performed with 124 international scar experts from 23 countries spanning 7 continents. Panelists rated their (dis)agreement with proposals regarding the wording and relevance of scar characteristics on a 5-point scale ("strongly disagree"to "strongly agree"), and provided arguments for their decisions. Consensus was reached if ≥67% of the panelists agreed or strongly agreed to a proposal. Results: Consensus was reached on the inclusion of 9 items. Two versions of the Observer Scale of the POSAS 3.0 have been developed, 1 generic version including 7 items, and 1 linear scar version, containing the same 7 items and 2 additional scar-specific items. Conclusions: This is the first study using the Delphi process to develop an instrument for the assessment of scars. Panelists from all over the world reached a consensus on the content of 2 versions of the Observer Scale, the generic version and the linear scar version. By involving the potential end-user community of the new POSAS version in its development, we expect the developed instrument to have high content validity. For a comprehensive scar assessment, the Observer Scale should be used in combination with the Patient Scales of the POSAS 3.0.