An assessment of the inter-rater and intra-rater reliability of the modified Gordon pin infection classification system.

Objectives: A grading system deployed for continuous at-home monitoring of pin sites would potentially increase the chances of early detection of pin-site infections and the commencement of early treatment. The first five grades of the Modified Gordon Pin Site Classification Scheme (MGS) meet the criteria for a visual-only, digital assessment-based grading system. The aim of this study was to assess the inter- and intra-rater reliability of the first five grades of the MGS from digital images.

Methods: We graded 1082 pin sites from 572 digital photographs of patients who underwent external fixator treatment for various conditions using the first five grades of the MGS classification scheme. Percent agreement and kappa values were calculated to determine the inter- and intra-rater agreement. Results were also grouped into two categories: "good" consisting of MGS grades 0-2 and "bad" made up of grades 3 and 4 for sensitivity analysis. We also analyzed reliability based on color only using MGS grades 0 and 2.

Results: A total of 843 of the 1082 pin sites were scored by all raters. There was moderate reliability between raters with a Fleiss kappa value of 0.48 [CI 0.45, 0.51]. The reliability remained moderate based on grouping into "good' versus "bad" and based on color with Fleiss kappa values of 0.48 [CI 0.45, 0.52] and 0.45 [CI 0.42, 0.49], respectively. Intra-rater reliability demonstrated substantial agreement with kappa values of 0.63.

Conclusion: Scoring pin sites from digital images with the MGS demonstrated only moderate inter-rater reliability. Modifying the use of digital photos is needed for at-home monitoring of pin sites.