Evaluation of agreement and correlation of results obtained with MRI-based and macroscopic observation-based grading schemes when used to assess intervertebral disk degeneration in cats

OBJECTIVE: To evaluate agreement in results obtained with an MRI-based grading scheme and a macroscopic observation-based grading scheme when used to assess intervertebral disk (IVD) degeneration in cats.

SAMPLE: 241 MRI and 143 macroscopic images of singular IVDs in 44 client-owned cats (40 cadaveric and 4 live).

PROCEDURES: Singular images of IVDs were obtained of live cats admitted for treatment of suspected neurologic disease (MRI images of IVDs) and of cadavers of cats euthanized for reasons unrelated to spinal disease (MRI and macroscopic images of IVDs) at the Small Animal Hospital, Vetsuisse Faculty, Zurich, Switzerland, between January 12, 2015, and October 19, 2015. The IVD images were randomized and evaluated twice by 4 observers for each grading scheme. Inter- and intraobserver reliability for the grading schemes was assessed with Cohen weighted κ analysis. Agreement and correlation between results obtained with the 2 grading schemes were determined with Cohen weighted κ and Spearman correlation coefficient (ρ) analyses, respectively.

RESULTS: Inter- and intraobserver agreement between results was substantial to almost perfect (mean weighted κ, 0.66 to 0.83 and 0.71 to 0.86, respectively) for the MRI-based grading scheme and moderate to substantial (mean weighted κ, 0.42 to 0.80 and 0.65 to 0.79, respectively) for the macroscopic observation-based grading scheme. Between the 2 grading schemes, agreement in results was moderate (mean ± SE weighted κ, 0.56 ± 0.05), and the correlation was strong (ρ = 0.73).

CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the MRI-based and macroscopic observation-based grading schemes used in the present study could be used reliably for classifying IVD degeneration in cats.