The reliability and validity of color indicators using digital image analysis of peristomal skin photographs: Results of a preliminary prospective clinical study

Accurate assessment is necessary to evaluate peristomal skin condition, but objective methods are lacking. The purpose of this prospective, repeated-measures study was to evaluate the reliability and validity of color indicators using digital image analysis of peristomal skin photographs. The 6-month study was conducted among 21 patients (mean age 65.1 years old, 15 men) with ostomies (14 colostomies, six ileostomies, and one urostomy) at four outpatient clinics. Photographs taken by nurses of the peristomal area using point-and-shoot cameras were processed using digital image analysis, which involved color calibration, image processing, and indicator calculation. An erythema index (EI), melanin index (MI), and hypopigmentation index were created to represent increased degrees of red, black, and white color, respectively, and their average values in the peristomal region of an image were calculated relative to values for intact skin. Reproducibility was evaluated using the interclass correlation coefficient (ICC). ICCs of color indicators for intact skin were >0.7 between baseline and the end of follow-up for the 16 participants with two or more clinic visits. Differences in these indices between peristomal and intact regions were evaluated using a linear mixed model. The EI and MI of peristomal skin were significantly higher than those of intact skin (n ≤ 42, P <0.001). All color indicators in adjacent regions and areas where adhesive was applied were associated with the discoloration severity score and visual analogue pain score (all P <0.05). This objective and simple method had adequate reproducibility and criterion-related validity and may be useful for peristomal skin assessment. Further research is warranted.