This was a randomized Control Trial, done in Department of Dermatology, Jinnah Postgraduate Medical Centre (JPMC), Karachi from August 22, 2020 to February 21, 2021.

A total of 202 patients with 101 in each group. The sample size was estimated using WHO sample size calculator using statistics for efficacy in topical Tazarotene gel (group A) as 30.5% and micro-needling (group B) as 47.2%,80% power of test and 95% confidence level. Both genders, 18 to 40 years with atrophic post-acne scar patients of duration 4 to 8 years were included. Informed consent was obtained. Patients with grade 2 to 4 facial atrophic post-acne scars assessed by Goodman and Baron qualitative global scarring grading system. While excluded pregnant/lactating woman, any prior allergy to given drug, history of keloidal tendency/hypertrophic scarring, active acne or acne marks such as red, black or brown macular marks, previous dermabrasion, laser resurfacing on face, facial scar due to reasons other than acne, collagen vascular disease, bleeding disorders, treatment history of \<4 weeks for topical retinoid, alpha/beta hydroxyl acids, \<3 months for microdermabrasion and \<6 months for oral retinoids.

This study was conducted after approval from ethical review committee and CPSP. During the patient first visit, baseline photographs were captured with informed consent. Dermoscopic examinations of predominant scar type (such as icepick, rolling or boxcar) and the ssca severity assessed according to the Goodman and Baron qualitative acne scarring grading systems for every patient. All patients were randomly divided into two groups using computer-generated sequential number placed in sealed envelopes and opened only before the commencement of the study. In group A, patients were instructed to apply a thin film of tazarotene gel 0.1% over the affected area once daily in the evening by placing a pea-sized amount of gel in the palm of the hand and using tip of a finger to cover the entire half of the face. Patients who experienced facial dryness were allowed to use a moisturizing cream during the day on entire face but use of any other medication on the face was prohibited. In group B, microneedling was performed with a standard dermaroller (192 needles of length 1.5 mm) by the same investigator, once per month for 6 months. A topical anesthetic mixture of lignocaine and prilocaine was applied over the face in a thick layer under occlusion 1 hour before the procedure.

Microneedling was performed by rolling the dermaroller with uniform and firm pressure in 4 different directions (i.e, perpendicular and diagonal to each other) with to-and-fro motion up to 8 times (a total of 32 passes) or until the end point of uniform pinpoint bleeding was achieved. After treatment, the area was wetted with saline pads. The participants were instructed to follow strict photoprotective measures including the application of a broad-spectrum sunscreen with sun protection factor 30 over the entire face. All patients were followed up at 3 month and on 6 month from the baseline visit. Digital photographs were captured at 3 and 6 month follow-up visits. An improvement by 2 qualitative grades was considered excellent, by 1 grade was rated good, and by 0 grade was labeled a poor response. The outcome was the change from baseline in acne scar severity grade at 3 and 6 month follow-up visits. All the data was entered in a predesigned proforma. Biasness and confounder were controlled by strictly following the inclusion criteria.

SPSS version 21 was used for data compilation and analysis. Frequencies and percentages were computed for qualitative variables like gender, scar type, treatment, scar severity grade at baseline, after 3 and 6 months and efficacy. Quantitative variables were presented as mean ± SD like age and duration of acne. Comparison between both groups for efficacy was done by using Chi square test. Effect modifier like age, gender and duration of disease were controlled through stratification. Post stratification, Chi square test was applied for categorical variables. Consider P \<0.05 as significant.