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Subjective Rating of Cosmetic Treatment with Botulinum Toxin Type A: Do Existing Measures Demonstrate Inter-observer Validity?
Nicole Conkling, BA/BS, Brett T. Phillips, MD, Muath M. Bishawi, BS, Duc T. Bui, MD, Sami U. Khan, MD, Alexander B. Dagum, MD.
Stony Brook University Medical Center, Stony Brook, NY, USA.

BACKGROUND:
Throughout the literature, investigators have assessed the cosmetic efficacy of Botulinum toxin (BT) treatment by employing various subjective, qualitative measures, including the Facial Wrinkle Scale (FWS) and Subject Global Assessment (SGA). The widely-used FWS and SGA attempt to quantify both the magnitude and duration of cosmetic outcomes as assessed by physician and patient. We sought to determine the inter-observer validity of these scales relative to the level of observer experience. We hypothesized that there is substantial inter-observer agreement among plastic surgeons in rating BT-treated patients using these scales.
METHODS:
BT injections were performed to cosmetic effect in 6 patients recruited as part of an Institutional Review Board-approved investigation. Subjects were photographed at rest and during animation (raising eyebrows, frowning, and blinking) prior to treatment and at 1 week, 2 weeks, 4 weeks, and monthly with follow-up to 6 months. Standardized digital 8”x10” prints were scored using the FWS, rating wrinkle severity from 0 (none) to 3 (severe), by Board-certified plastic surgeons (n=5), general surgery residents (n=3), and medical students (n=4). Photos at each time point were then compared to baseline, rating percent change using the SGA. The observers were instructed to use the scales to their best judgment and were blinded to each other’s scores. Statistical analysis of observer data was performed using SPSS v19. Cohen’s kappa (FWS) and Spearman’s rho (SGA) were calculated for each pair-wise comparison of observer data, with a conservative alpha of 0.01.
RESULTS:
FWS observer scores were in agreement overall (Table 1), with no negative kappa values. The distribution, even among members of a single group, was highly variable (Figure 1). As hypothesized, agreement among plastic surgeons was the greatest (kappa=0.194-0.609). Resident concordance was moderate, and medical students displayed the most variable agreement. Spearman’s rho for SGA scores was much higher, with surgeons approaching excellent agreement (0.443-0.992). In pair-wise comparisons between members of different groups, agreement was unpredictable and ranged from slight to good for both the FWS and SGA.
CONCLUSIONS:
The FWS and SGA represent the current standard of cosmetic outcomes measures; however, our data demonstrate that when subjected to scrutiny they display unpredictable agreement even among plastic surgeons. Compared to the FWS, the SGA has a more acceptable user concordance, especially among plastic surgeons accustomed to using such scales. These data underline the need to explore objective, quantitative outcomes metrics for cosmetic patients.


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