Interobserver Agreement in Clinical Grading of Vitreous Haze Using Alternative Grading Scales

Purpose: To evaluate the reliability of clinical grading of vitreous haze using a new 9-step ordinal scale versus the existing 6-step ordinal scale. Design: Evaluation of diagnostic test (interobserver agreement study). Participants: A total of 119 consecutive patients (204 uveitic eyes) presenting for uveitis subspecialty care on the study day at 1 of 3 large uveitis centers. Methods: Five pairs of uveitis specialists clinically graded vitreous haze in the same eyes, one after the other using the same equipment, using the 6- and 9-step scales. Main Outcome Measures: Agreement in vitreous haze grade between each pair of specialists was evaluated by the kappa statistic (exact agreement and agreement within 1 or 2 grades). Results: The scales correlated well (Spearman's rho = 0.84). Exact agreement was modest using both the 6- step and 9-step scales: average kappa = 0.46 (range, 0.28-0.81) and kappa = 0.40 (range, 0.15-0.63), respectively. Within 1-grade agreement was slightly more favorable for the scale with fewer steps, but values were excellent for both scales: kappa = 0.75 (range, 0.66-0.96) and kappa = 0.62 (range, 0.38-0.87), respectively. Within 2-grade agreement for the 9-step scale also was excellent (kappa = 0.85; range, 0.79-0.92). Two-fold more cases were potentially clinical trial eligible on the basis of the 9-step than the 6- step scale (P<0.001). Conclusions: Both scales are sufficiently reproducible using clinical grading for clinical and research use with the appropriate threshold (>= 2- and >= 3-step differences for the 6- and 9-step scales, respectively). The results suggest that more eyes are likely to meet eligibility criteria for trials using the 9-step scale. The 9-step scale appears to have higher reproducibility with Reading Center grading than clinical grading, suggesting that Reading Center grading may be preferable for clinical trials. (C) 2014 by the American Academy of Ophthalmology.