Effect of computer monitor brightness on visual (subjective) carotid plaque characterization

Visual carotid plaque classification on duplex imaging is moderately reproducible, and, although the literature is controversial, research to analyze and overcome this problem remains scarce. The aim of this study was to assess the effect of computer screen brightness on the intraobserver variation of visual plaque classification.

One hundred asymptomatic noncalcified carotid plaques causing carotid stenosis >40% on duplex scanning, in 84 patients, were transferred to a personal computer, normalized, and classified into four groups of increasing echogenicity (types 1-4) at 50% and 100% of maximum monitor brightness settings. Baseline intraobserver variability of visual plaque classification at maximum brightness was also assessed.

Baseline intraobserver variability was moderate (Cohen's Kappa value 0.59, p < 0.001). Reduction in monitor brightness caused a systemic shift in echogenicity, with 51% of the type 2-4 plaques being classified as more echolucent. Likewise, Cohen's Kappa value decreased to 0.37, indicating poor agreement between the two classification rounds.

Reduction in computer screen brightness deteriorates the intraobserver variation of visual plaque classification. This finding could explain some of the discrepancy in reproducibility results reported and should be taken into account when using visual characterization methods.