Performance assessment of the Double Plate method (ISO23675) in ALT-SPF Consortium: A highly reproducible and accurate in vitro method to determine SPF

IF 2.5 4区医学 Q2 DERMATOLOGY

International Journal of Cosmetic Science Pub Date : 2025-09-01 DOI:10.1111/ics.13088

Florence Pouradier, Sebastien Miksa, Jan Batzer, Modibo Mangassi, Anna Ludwikowska, Hicham Nocairi, Bertrand Colson, Gerald Renner, Paul J. Matts, Marc Pissavini

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Abstract

Objective

To perform a comprehensive statistical characterization of the Double Plate method (ISO 23675) as a potential in vitro alternative to the in vivo reference method (ISO 24444:2019) for determining the sun protection factor (SPF).

Methods

Five qualified laboratories were involved in testing the Double Plate method, as part of a large-scale ring test conducted by the International Consortium ‘ALT-SPF’. About 32 sunscreen products, reflecting diverse global formulations, were tested using both the in vivo reference method and the Double Plate method. This method employs spectrophotometric measurements of sunscreen applied to UV-transparent plates with standardized robotic application to minimize the variability. A mathematical adjustment was introduced to address the initial bias compared to the reference method and further assessed in a follow-up ring test with 12 products, including ISO standards.

Results

The Double Plate method exhibited very high intra- and inter-laboratory reproducibility throughout the study, consistently meeting the precision criteria set by ISO/TC217/WG7. Following the mathematical adjustment, the accuracy significantly improved, demonstrating a close alignment with the reference method.

Conclusion

The Double Plate method demonstrates excellent reproducibility and, following optimization, high accuracy for the SPF determination. These findings endorse the Double Plate method as a robust and ethical in vitro alternative to the in vivo reference method for SPF testing. This paved the way for its publication as a new ISO standard (ISO 23675), in December 2024, supporting consumer safety and informed product choices.

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ALT-SPF联盟双板法（ISO23675）的性能评价：一种高重复性、高准确度的体外SPF测定方法

目的对双板法（ISO 23675）作为体内参考法（ISO 24444:2019）测定防晒系数（SPF）的潜在体外替代方法进行综合统计表征。方法在国际联盟“ALT-SPF”进行的大规模环试验中，有5个合格的实验室参与双板法的试验。大约32种防晒产品，反映了不同的全球配方，使用体内参考法和双板法进行了测试。该方法采用分光光度法测量防晒霜应用于紫外线透明板与标准化的机器人应用，以尽量减少可变性。引入数学调整来解决与参考方法相比的初始偏差，并在后续的12种产品（包括ISO标准）的环形测试中进一步评估。结果双板法在整个研究过程中具有非常高的实验室内和实验室间重复性，始终符合ISO/TC217/WG7设定的精密度标准。经数学平差后，精度显著提高，与参考方法接近。结论双板法重现性好，经优化后具有较高的SPF测定准确度。这些发现支持双板法作为一个可靠的和道德的体外替代在体内的参考方法进行SPF测试。这为其作为新的ISO标准（ISO 23675）于2024年12月发布铺平了道路，支持消费者安全和知情的产品选择。

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来源期刊

International Journal of Cosmetic Science DERMATOLOGY-

CiteScore

4.60

自引率

4.30%

发文量

期刊介绍： The Journal publishes original refereed papers, review papers and correspondence in the fields of cosmetic research. It is read by practising cosmetic scientists and dermatologists, as well as specialists in more diverse disciplines that are developing new products which contact the skin, hair, nails or mucous membranes. The aim of the Journal is to present current scientific research, both pure and applied, in: cosmetics, toiletries, perfumery and allied fields. Areas that are of particular interest include: studies in skin physiology and interactions with cosmetic ingredients, innovation in claim substantiation methods (in silico, in vitro, ex vivo, in vivo), human and in vitro safety testing of cosmetic ingredients and products, physical chemistry and technology of emulsion and dispersed systems, theory and application of surfactants, new developments in olfactive research, aerosol technology and selected aspects of analytical chemistry.