Validating the Reliability and Clinical Relevance of a Nasolabial Fold Photonumeric Scale
January 2024 | Volume 23 | Issue 1 | 1319 | Copyright © January 2024
Published online December 11, 2023
Z.Paul Lorenc MD FACSa, Stacy Smith MDb, Lawrence S. Bass MD FACSc, David Bank MDd, Robert Weiss MDe, Doug Canfield BSf, Brian M. D'Alessandro PhDf, Lisa M. Cramer BAf
aPlastic Surgeon in Private Practice - New York, NY; Department of Plastic Surgery, Lenox Hill Hospital, New York, NY
bCalifornia Dermatology & Clinical Research Institute, Cardiff, CA
cZucker School of Medicine at Hofstra/Northwell; Private Practic New York, NY
dThe Center for Dermatology, Cosmetic & Laser Surgery/Private Practice Mt. Kisco, NY
eDepartment of Dermatology, University of Maryland, Baltimore, MD; Maryland Dermatology Laser Skin & Vein, Hunt Valley, MD
fCanfield Scientific Inc. Parsippany, NJ
Abstract
Background: The use of tissue fillers to treat age-related deepening of the nasolabial fold (NLF) has increased and become the standard clinical approach, creating a need for evidence-based, objective evaluation for pre- and post-procedure assessment of the NLF.
Methods: A 5-point rating scale was developed to assess the NLF, specifically the presence of depression and shadowing. Live validation of the scale was performed with a total of 73 participants representing the full range of NLF severities. Physicians board-certified in a core aesthetic specialty (3 trained raters) performed the scale validation over 2 rounds, 2 weeks apart. Training was carried out, and test-retest reliability was quantitated through the determination of intra- and inter-rater reliability by percentage of agreement, weighted kappa statistic with 95% confidence interval (CI), and intraclass correlation coefficient with 95% CI. To evaluate the clinical relevance of a 1-grade difference, rater assessments of 90 photo pairs were compared with previous designations of clinically different or not clinically different.
Results: The NLF scale achieved near-perfect intra- and inter-rater reliability when utilized by trained raters to assess a diverse group of live participants. Furthermore, clinically relevant differences between grades were established, and a 1-point difference was detectable by trained evaluators using the NLF scale.
Conclusion: The clinically relevant and highly reliable validated NLF scale provides a standardized grading system with a user-friendly design for objectively assessing NLF in clinical practice and as a research tool for clinical approval studies of new aesthetic products and technologies.
J Drugs Dermatol. 2024;23(1):1284-1291. doi:10.36849/JDD.7316
INTRODUCTION
Formation of wrinkles and folds due to age-related loss of fat, muscle, and bone mass, and changes in skin characteristics can have a negative impact on an individual’s appearance, and in some cases affect psychological and social well-being.1-3 The nasolabial folds extend symmetrically from the ala nasi, cheek, and upper lip junction to below the lateral corner of the mouth, following a straight, convex, or concave path. In the midface, loss of deep fat volume and muscle contour, in combination with age-related bone absorption in the malar area as well as flattening of the central mid-cheek, exaggerates the depth of the nasolabial folds (NLFs).3-5 Deepening of the NLF is a common complaint in the aesthetics practice, and has been rated among the more bothersome facial defects for which more mature patients are likely to seek aesthetic treatment.5-7 Over the past 2 decades, soft tissue augmentation using fillers has become the standard clinical approach for treating NLF, and innovations in filler and device technology continue to give rise to new tools to address this concern.3,5,6 With the evolution in the treatment of NLF comes the need for evidence-based, objective evaluation. To meet this demand, several scales have been developed to assess wrinkle depth and NLF severity, improving over time with the integration of photonumeric scales using standardized methods of photography.8-14 For adoption in clinical practice, rating scales should be clinically relevant and have high test-retest reliability, which can be quantitated through intra- and inter-rater reliability using Cohen's weighted kappa coefficient and intraclass correlation coefficient (ICC). These coefficients are numbers between 0 and 1, where 1 corresponds to exact reproducibility and 0 represents an agreement that occurs by chance.15,16 The purpose of this study is to validate a newly developed, high-quality, 5-point photonumeric scale that includes photometric modelling of scale images (Table 1), for the assessment of NLF. Assessments establish test-retest
