Evaluating change in bruise colorimetry and the effect of subject characteristics over time

Forensic clinicians are routinely asked to estimate the age of cutaneous bruises. Unfortunately, existing research on noninvasive methods to date bruises has been mostly limited to relatively small, homogeneous samples or cross-sectional designs. Purpose: The purpose of this prospective, foundational study was to examine change in bruise colorimetry over time and evaluate the effects of bruise size, skin color, gender, and local subcutaneous fat on that change. Method: Bruises were created by a controlled application of a paintball pellet to 103 adult, healthy volunteers. Daily colorimetry measures were obtained for four consecutive days using the Minolta Chroma-meter®. The sample was nearly equal by gender and skin color (light, medium, dark). Analysis included general linear mixed modeling (GLMM). Results: Change in bruise colorimetry over time was significant for all three color parameters (L*a*b*), the most notable changes being the decrease in red (a*) and increase in yellow (b*) starting at 24 h. Skin color was a significant predictor for all three colorimetry values but sex or subcutaneous fat levels were not. Bruise size was a significant predictor and moderator and may have accounted for the lack of effect of gender or subcutaneous fat. Conclusion: Study results demonstrated the ability to model the change in bruise colorimetry over time in a diverse sample of healthy adults. Multiple factors, including skin color and bruise size must be considered when assessing bruise color in relation to its age. This study supports the need for further research that could build the science to allow more accurate bruise age estimations.