Table 1 Median DNA damage measured by the standard comet assay and the Fapy‐DNA‐glycosylase‐ modified comet assay before and after methylene blue and indigo carmine dye spraying in the two groups of patients.

Patient group	n	Median DNA damage (IQR) before spraying (%)	Median DNA damage (IQR) after spraying (%)	p Value (Wilcoxon's test)
IC spraying (standard comet assay)	10	7.2 (5.1–15.8)	5.3 (4.1–11.7)	0.084
IC spraying (FPG‐modified comet assay)		10.5 (6.0–32.1)	12.3 (5.9–17.3)	0.492
MB spraying (standard comet assay)	10	5.9 (4.9–8.1)	12.0 (5.2–19.8)	0.014
MB spraying (FPG‐modified comet assay)		9.8 (7.5–14.0)	34.3 (23.9–58.8)	0.002

FPG, Fapy‐DNA‐glycosylase; IC, indigo carmine; IQR, interquartile range; MB, methylene blue.

Biopsy samples were digested with 100 µl of 0.5% pronase and 100 µl of 0.3% collagenase in 800 µl DMEM at 37°C for 1 h, to create a single‐cell suspension for comet assay analysis.