Introduction and validation of a new histological scoring system for classification of intervertebral disc degeneration in dogs
Nies, K.S. de
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Introduction: Low back pain is a common disorder in both humans and dogs and is frequently caused by intervertebral disc degeneration (IVDD). In contrast with IVDD in humans, there is no published system for scoring histological changes in IVDD in dogs. Therefore a clear, unambiguous, descriptive, and repeatable histological scoring system is needed. Aim of the study: Designing and validating a histological scoring system for the classification of IVDD in dogs. Material and methods: Twenty-five intervertebral discs from ten dogs were used in a pilot study to evaluate 15 different histological parameters  for histological grading of IVDD. The gross morphologic grading according to Thompson  was used as a gold standard. The grading was performed twice by two independent observers. The histology parameters and the total histology score for each IVD were correlated with the Thompson grades using Spearman’s rank test (p=0.01). The inter- and intra-observer reliability were assessed by means of a weighted Kappa analysis. Results and conclusion: Significant correlation with the gold standard was found for most histological parameters and the total histology score was significantly correlated to the Thompson score (r= 0.856). Most parameters showed a weighted Kappa value between 0.430 - 0.889, indicating ‘moderate’ to ‘almost perfect’ inter-observer reliability. The intra-observer reliability for the total histology score was ‘substantial’ with 0.746 and 0.627 for observer one and two, respectively. Nine parameters, encompassing all parts of the IVD, based on the highest correlation to the gold standard and/or the highest repeatability, were selected for the histological scoring system that is proposed for the future classification of IVDD in dogs. 1. Boos, N., et al., Classification of age-related changes in lumbar intervertebral discs: 2002 Volvo Award in basic science. Spine, 2002. 27(23): p. 2631-44. 2. Thompson, J.P., et al., Preliminary evaluation of a scheme for grading the gross morphology of the human intervertebral disc. Spine, 1990. 15(5): p. 411-5.