J. Cosmet. Sci., 70, 181–196 (July/August 2019) 181 Disparate SPF Testing Methodologies Generate Similar SPFs. II. Analysis of P2 Standard Control SPF Data MELANNIE ALEJANDRIA, ANDREW MARRA, GLENN ROBERTS, and MICHAEL CASWELL , Consumer Product Testing Company, Inc., Fairfi eld, NJ (M.A., A.M., G.R., M.C.) Accepted for publication May 26, 2019. Synopsis In the original scientifi c publication evaluating sunscreen methodologies, Garzarella and Caswell showed there to be no clinically signifi cant or statistically signifi cant difference in the average Sun Protection Factor (SPF) of a sunscreen formulation between any of three methodologies, Food and Drug Administration (FDA) Final Monograph, Australia/New Zealand, and European Cosmetics Association (COLIPA) International, suggesting that any differences in methodology were insignifi cant in the resulting SPF determined. These three major older methodologies have coalesced into two methodologies, 2011 FDA-Final Rule and ISO 24444, so that current sunscreen SPF testing is mostly 2011 FDA-Final Rule and ISO 24444. Another approach to evaluating the impact of methodological differences in sunscreen testing is to compare data on a control standard or reference sunscreen. If the difference between the two SPF values of P2 is statistically signifi cant for the two different methodologies, then this would present evidence for a clinically signifi cant difference in the SPF value between the two methodologies. For 2011 FDA-Final Rule, the expected SPF of P2 is 16.3 ± 3.43 for ISO 24444, the expected SPF of P2 is 16.1 ± 2.42. Using least squares average and standard error on 952 observations, the 2011 FDA-Final Rule SPF of P2 is 15.4 ± 0.12 using least squares average and standard error on 1,551 observations, the ISO 24444 SPF of P2 is 15.6 ± 0.10. The data described herein indicate no clinically signifi cant nor statistically signifi cant difference between the SPF average of P2 using the 2011 FDA-Final Rule methodology versus that using ISO 24444 methodology. Further statistical analysis indicates that the average SPF of P2 is independent of solar simulator type, time of year (month), age of subject, gender of subject, or Fitzpatrick Skin Phototype of subject. A statistically signifi cant negative correlation was found between a subject’s SPF of P2 and the subject’s unprotected minimal erythemal dose. The implications of this relationship on SPF testing are explored. INTRO DUCTION The t hree major older methodologies for sunscreen testing, Food and Drug Administration- Final Monograph (FDA-FM) method (1,2), Australia/New Zealand (Aus/NZ) method (3), and COLIPA International (International) method (4,5) have coalesced into two method- ologies, 2011 FDA-Final Rule (6) and ISO 24444 (7). Examining data from sunscreen testing, Garzarella and Caswell (8) showed there to be no signifi cant difference in the Address all correspondence to Michael Caswell at mcaswell@cptclabs.com
JOURNAL OF COSMETIC SCIENCE 182 average Sun Protection Factor (SPF) of a sunscreen formulation between any of the three older methodologies. Their data suggested that any differences in methodology were in- signifi cant in the resulting SPF determined. Anoth er approach to evaluating the impact of methodological differences in sunscreen testing is to compare data on a control standard or reference sunscreen. A control stan- dard, P2, P3, or P7, must be run concurrently on every subject undergoing SPF testing, regardless of which method is being used. P2, with actives of 7% ethylhexyldimethyl PABA (Padimate O) and 3% benzophenone-3, is a control standard for 2011 FDA-Final Rule (6) and for ISO 24444 (7). Although the 2011 FDA-Final Rule does not refer to this control standard as P2, for simplicity in this document, this control standard will be re- ferred to as P2. For 2011 FDA-Final Rule, the expected SPF of P2 is 16.3 ± 3.43 (6) for ISO 24444, the expected SPF of P2 is 16.1 ± 2.42 (7) (Table I). If the difference between the two SPF values of P2 is statistically signifi cant for the two different methodologies, then this would present evidence for a clinically signifi cant difference in the SPF value between the two methodologies. The dat a described herein indicate no statistically signifi cant difference between the SPF average of P2 using the 2011 FDA-Final Rule methodology versus that using ISO 24444 methodology. Further statistical analysis indicates that the average SPF of P2 is indepen- dent of solar simulator type, time of year (month), age of subject, gender of subject, or Fitzpatrick Skin Phototype of subject. However, consistent with the hypothesis of Damian et al. (9), the data presented herein clearly show a statistically signifi cant negative correla- tion between a subject’s SPF of P2 and the subject’s unprotected Minimal Erythemal Dose (MED). As a subject’s unprotected MED decreases, the subject’s SPF of P2 increases. The implications of this relationship on SPF testing are explored. METHODS The sta ndard control, P2, was obtained from Cosmetech Laboratories, Inc., Fairfi eld, NJ. The lot numbers used were 1902D, 1902E, 1902F, 1902G, 1902H, 1902I, and 1902J. The cli nical trials were approved by Allendale IRB, Old Lyme, CT, Dr. Robert Staab, Chairperson. The trials were conducted at Consumer Product Testing Company, Inc., located in Fairfi eld, NJ, according to the principals of the Declaration of Helsinki (as amended) (10) and the Belmont Report (11) and according to ICH GCP and the Standard Operating Procedures at Consumer Product Testing Company, Inc. Each potential subject was apprised of the risks and benefi ts of the research clinical trial before conducting any procedures. Once the potential subject consented to participate, their consent was cap- tured through the execution of an Informed Consent Document by the potential subject Table I Expected SPF Values o f the Control Standard for ISO 24444 and for 2011 FDA-Final Rule Method Mean Standard deviation Reported Herein Least square average Standard error Mean Standard deviation ISO 24444 16.1 2.42 15.6 0.10 15.7 2.40 2011 FDA 16.3 3.43 15.4 0.12 15.4 2.57
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