Test design and results of a method performance characterization study for SPF and UVA-PF testing

Area of Science:

• Dermatology and Photobiology
• Analytical Chemistry
• Cosmetic Science

Background:

• Standardized testing is crucial for sunscreen efficacy claims.
• Existing ISO methods (24444 for SPF, 24443 for UVA-PF) serve as benchmarks.
• Characterizing alternative methods ensures reliable and comparable results.

Purpose of the Study:

• To evaluate the performance of alternative SPF and UVA-PF testing methods.
• To compare these methods against established ISO 24444 and ISO 24443 standards.
• To identify sources of variation in sunscreen testing.

Main Methods:

• A factorial experimental design was employed with 32 sunscreens across eight product groups.
• Four participating laboratories were involved to ensure statistical reliability.
• Performance criteria included reproducibility precision, between-laboratory variation, and bias.

Main Results:

• Performance characteristics and reproducibility/repeatability limits for the reference methods are presented.
• Analysis identified main sources of variation for both ISO 24444 and ISO 24443.
• Precision was characterized for each of the eight product groups.

Conclusions:

• The precision of ISO 24444 and ISO 24443 was successfully characterized.
• Key sources of variation influencing test results were identified.
• Reproducibility and repeatability limits provide valuable data for method validation.