OBJECTIVE: Acne scarring is a common and frustrating consequence of acne vulgaris. Recently, there have been huge advancements in photoelectric therapies for scarring, leading to a growing body of literature on the efficacy and safety of these devices. However, interventional studies are hindered by the absence of standardized and validated outcome measures for acne scarring. Therefore, this manuscript aims to review current grading modalities to assist clinicians in conducting acne scar research and therapies. DESIGN: The authors used PubMed and MEDLINE online to identify acne scarring severity measurements. Each was classified into objective technologies, subjective investigator-reported, or subject-reported assessments and evaluated based on reliability, sensitivity, validity, and other important aspects. RESULTS: Objective instruments for assessing clinical efficacy in acne scarring show promise, especially PRIMOS, a 3D imager with strong inter-rater reliability (ICC >
0.90) or intra-rater reliability (ICC >
0.96) and validation by other subjective scales. Regarding subjective assessments, the ECCA system features the widest range of applications and shows acceptable performance, scoring 5 out of 8 points according to its reliability, sensitivity, and validity. The GSGS score has also obtained a desirable score of 7 out of 8. However, most scales demonstrated poor or moderate performance due to the lack of reliability testing and evidence for independent assessment. CONCLUSION: This review of acne scarring measurements shows that PRIMOS stands out as a strong objective tool, whereas GSGS and ECCA are the leading subjective scales with acceptable to strong performance. More importantly, there's the need for standardized scales, facilitating the pooling of results for systematic reviews, meta-analyses, and clinical recommendations.