Years ago, when I first became involved in acne research, I was struck by the variability and lack of standardization in how acne was evaluated. I understood then as I do now, the importance of accurate, effective and practical measures in assessing this common condition.
This matters in clinical practice because dermatologists need practical ways to follow patient progress over time. It is even more critical in clinical trials, where efficacy outcome measures help determine whether a treatment truly works, how well it works and in whom. I have often wondered how many promising innovations have failed not because the treatment lacked value but because the outcome measures were inadequate, or because investigators were not sufficiently trained and calibrated in their use. Properly developed and validated measures coupled with investigator training and testing, are essential to ensuring accuracy in determining the true value of new treatments.
Thus, my academic interest in acne research began with a simple and practical question: how do we know that we are measuring acne severity properly? And just as importantly, from whose perspective?
Variability in Acne Lesion Counting and Global Grading
One of the first issues I encountered was the variation in acne lesion counting and global grading of acne severity. It was clear to me that dermatologists did not always count lesions or grade acne severity in the same way.
For lesion counting, there was extensive variability, even amongst acne experts evaluating the same acne patients. Variability was also present in global grading. One important issue was that some evaluators focussed only on primary acne lesions while others also included scars and pigmentation in their overall assessment of severity.
This distinction matters. Interventions for active acne focus on:
- Comedones
- inflammatory papules
- Pustules
- Nodules
They are not usually designed to improve sequelae such as scarring and hyperpigmentation. While all of these lesion types can adversely affect patients they should not be conflated into an efficacy outcome measure intended to assess active acne.
This need for clarity led me to lead and publish on a consensus project involving global acne experts in understanding what should comprise the ideal acne global grading scale. From these findings, we then explored which current scales, if any, could be suitable as a potential ideal.
Standardizing Acne Lesion Counting and Grading
In investigator training sessions for acne clinical trials, another practical problem was that there was no gold standard teaching model for acne lesions in terms of types or lesion numbers.
To address this, I developed facial silicone faces with pre-established acne lesion types and counts. The goal was to create a standardized teaching and testing model for acne lesion counting, so that investigators could be trained and assessed in a more consistent way.
This was an effort subsequently used by Galderma for investigator meetings and site qualification, illustrating how a practical clinical observation could be translated into a tool directly relevant for clinical research.
For acne grading, I also developed a series of standardized virtual facial images across different skin phototypes. These were designed to represent varying severities of acne in a manner aligned with the US FDA recommendations for acne clinical trials.
Acne Beyond the Face: The Comprehensive Acne Severity Scale
For decades, acne evaluations in clinical trials only focused on facial involvement. However, this anatomic restriction was inadequate. People with acne also have involvement of the chest and back, which can be bothersome and distressing.
To address this gap, I developed the Comprehensive Acne Severity Scale, or CASS. This scale includes global assessments of acne severity on the face, chest and back thereby encompassing the most affected regions in acne. This was important as truncal acne had been under-recognized in clinical practice and clinical trials, despite being common, bothersome, and relevant to patient quality of life.
The rationale was that our outcome measures should reflect the reality of acne which affects not just the face but also the trunk.
Including the Patient Voice
The patient voice is essential to understand the true impact of acne. Acne is readily visible and affects self-confidence, social interactions, mood, relationships and quality of life.
While other acne quality of life scales had been developed, none prior to the Comprehensive Acne Quality of Life scale or CompAQ, adequately addressed truncal acne. CompAQ was developed as a psychometrically validated patient-reported outcome measure intended to capture the broader impact of acne, including acne affecting the face, chest and back.
This was important because we had previously shown that clinician assessment and patient burden are not always aligned. A treatment may reduce lesions, but the patient’s perception of improvement in symptoms, confidence and psychosocial burden also matters.
Acne Scarring
Acne scarring can be a devastating and persistent consequence of acne. Furthermore, it can be extremely frustrating and bothersome to patients with significant impacts on quality of life.
Despite this, there were few simple global scales available to grade overall acne scarring in a practical and clinically useful way. I developed the Severity Scale for Acne Scarring (SCAR-S) to help address this unmet need in both clinical research and patient care.
The goal was to provide a simple, global assessment of acne scarring that could be useful in both clinical practice and clinical trials in acne.
Towards Better Outcome Measures in Acne
An extension of my academic and clinical trials work in acne was involvement as a co-investigator in a US National Institutes of Health initiative – the Acne Core Outcomes Research Network. In collaboration with Prof Diane Thiboutot of Penn State, USA and Prof Alison Layton of Leeds University, UK, the objective was to develop a core outcome set for acne clinical trials with potential relevance to clinical practice as well.
The broader aim of all this work has been to improve how acne is measured, to make assessments more accurate and reliable, and to ensure that both clinician evaluation and patient experience are considered.
Better outcome measures have important implications across dermatology:
- For clinical care: They help clinicians gauge patient progress more accurately and align treatment goals more closely with patients.
- For clinical trials: They help determine whether a treatment truly works, how well it works, for whom it works, and which aspects of acne it improves.
- For industry and clinical trial partners: They ensure that new treatments are evaluated using outcome measures that are appropriate, validated, properly applied by investigators and study sites, and meaningful to both regulatory authorities and patients.
In acne, as in other areas of dermatology, better measurement leads to better evidence, which leads to better treatment decisions. Ultimately, this should translate into better outcomes for people living with acne.
Selected References
Tan JK, Fung K, Bulger L. Reliability of dermatologists in acne lesion counts and global assessments. J Cutan Med Surg. 2006 Jul-Aug;10(4):160-5.
Tan J, Wolfe B, Weiss J et al. Acne severity grading: determining essential clinical components and features using a Delphi consensus. J Am Acad Dermatol. 2012 Aug;67(2):187-93
Tan JKL, Jones E, Allen E et al. Evaluation of essential clinical components and features of current acne global grading scales. J Am Acad Dermatol. 2013 Nov;69(5):754-761.
Tan JK, Tang J. Three-dimensional, Full-sized, Silicone-based, Facial Replicas for Teaching Outcome Measures in Acne. J Clin Aesthet Dermatol. 2010 Jun;3(6):35-8.
Tan JK, Tang J, Fung K et al. Development and validation of a comprehensive acne severity scale. J Cutan Med Surg. 2007 Nov-Dec;11(6):211-6.
McLellan C, Frey MP, Thiboutot D et al. Development of a Comprehensive Quality-of-Life Measure for Facial and Torso Acne. J Cutan Med Surg. 2018 May/Jun;22(3):304-311.
Tan JK, Tang J, Fung K et al. Development and validation of a Scale for Acne Scar Severity (SCAR-S) of the face and trunk. J Cutan Med Surg. 2010 Jul-Aug;14(4):156-60.
Tan J, Thiboutot D, Layton A, Miklas M. Developing a Core Outcome Set for Acne Clinical Trials: Towards Standardization and Harmonization. In: Suh DH, editor. Acne. Updates in Clinical Dermatology. Cham: Springer International Publishing; 2021. p. 25–33
