Quantifying the Degree of Bruise Visibility Observed Under White Light and an Alternate Light Source

Documentation of injuries associated with abuse and assault has pivotal impacts on clinical and legal outcomes. Before this study, no reliable and valid tools to consistently document the clinical visibility of bruises existed. The purpose of this study was to systematically evaluate reliability and validity of the Bruise Visibility Scale for documenting bruises visualized in normal (white) light and the Absorption Visibility Scale for documenting bruises visualized using an alternate light source (ALS).

Bruises were induced using a paintball on the upper arms of 157 participants stratified into six skin color categories. Bruises were visualized 21 times over 4 weeks under white light and 10 ALS wavelength/goggle color combinations. Bruise size was measured using a metric ruler; bruise color was measured using a spectrophotometer. Interrater reliability was calculated using kappa and intraclass correlations coefficients. Construct validity was evaluated using generalized linear mixed modeling of associations between bruise size and color with both visibility scales.

Interrater agreement for bruise detection was over 90% for all but two ALS wavelength/goggle combinations. Kappa values indicated adequate interrater agreement under white light (κ = 0.76) and ALS (κ = 0.78). The visibility scale intraclass correlation coefficients were .91 for normal light and .93 for ALS. Statistical modeling showed greater bruise size was associated with higher visibility using either scale, and greater contrast in color or lightness was associated with higher Bruise Visibility Scale values.

Both visibility scales showed satisfactory reliability and validity. Forensic nurses can use the scales to consistently document bruises.