Analyses Of The Influencing Factors Of Q-switched Lasers In Tattoo Removal And Applications Of Kirby-Desai Scale In Predicting The Efficacy

Objective To observe the clinical efficacy and safety of Q-switched lasers in tattoo removal,analyze the variables influencing the outcome by univariate analysis and multivariate analysis,and investigate the role of Kirby-Desai scale in predicting the efficacy of tattoo removal by Qswitched lasers.Methods A total of 385 tattoos were collected from 333 patients who first visited Hangzhou Third People’s Hospital from January 2014 to December 2020.All the patients were treated with the Q-switched 755nm alexandrite laser and/or the Q-switched 532/1064nm Neodymiumdoped Yttrium Aluminum Garnet laser according to the color of the tattoo.The appropriate wavelength,energy density,spot size and repetition rate are selected according to the patients’responses to the Q-switched lasers.The clinical efficacy and safety of tattoo removal by Qswitched lasers were observed.Univariate analysis of different genders,ages,Fitzpatrick skin types,tattoo types,scarring and tissue change,tattoo locations,tattoo size,amount of ink,tattoo color,tattoo duration and treatment sessions in the therapeutic effect of tattoo removal by Qswitched lasers were conducted.Multivariate logistic regression analysis was carried out for indexes with obvious differences.In addition,we investigated the role of Kirby-Desai scale in predicting the efficacy of tattoo removal by Q-switched lasers.Results The effective rate of 385 tattoos after the first Q-Switched laser therapy was 57.7%.After an average of 3.56（2-13）treatments,the effective rate was 90.4%.81.0%of the tattoos had immediate adverse reactions after the laser treatment,including erythema,edema,purpura,bleeding,blister or bullae formation,etc.Delayed adverse reactions were noticed in 19.2%of the tattoos,including skin texture change,scar,hyperpigmentation or hypopigmentation.Univariate analysis showed that treatment sessions,tattoo type,tattoo location,amount of ink and tattoo size had statistical significance in the overall therapeutic effect（P<0.05）.However,there were no significant differences in gender,age,skin Fitzpatrick type,tattoo color,scarring and tissue change and tattoo duration in the overall therapeutic effect（P>0.05）.Multivariate regression showed that treatment sessions,tattoo type,tattoo location and amount of ink were independent predictors.The median Kirby-Desai scores of 10（8,12）was significantly correlated with the actual number of treatments of 4（3,6）among 122 cured tattoos,the correlation was relatively low（r=0.372,P<0.05）.Conclusion Q-switched laser can remove the tattoo pigment effectively by selective photothermal,photochemical effects and photomechanical effects,with mild adverse reactions.Univariate and multivariate analysis showed that the most important factors affecting the efficacy of tattoo removal by Q-switched lasers may be the treatment sessions,tattoo location and amount of ink.The Kirby-Desai scale can predict the efficiency of tattoo removal by Qswitched lasers to some extent and is worth promoting clinically after appropriate modification.However,more large-sample,high-quality,prospective,randomized controlled studies are wanted in the future.