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Multi-laboratory validation of very high sun protection factor values
Joseph W Stanfield1, Hao Ou-Yang, Theresa Chen
1Suncare Research Laboratories LLC, Winston-Salem, NC, USA.
Background:
High sun protection factor (SPF) sunscreens have multiple benefits but there has not been validation of the test method for determining SPF values higher than 50. This study addresses specifically the accuracy and reproducibility of the high SPF test.
Methods:
Two high SPF formulations with a standard reference (SPF 15) were tested at four independent test facilities according to the 2007 FDA proposed amendments to the sunscreen monograph. Statistical analysis was performed to compare the SPF results within each lab as well as the SPF results between different labs.
Results:
The test formulations have overall mean values of 90.5 and 70.7. There was no statistically significant difference between the labs for either formulation and all four labs were able to statistically differentiate these two levels of SPF values. The coefficients of variance (CV) for the high SPF formulations were comparable to those of the corresponding SPF 15 reference within each lab.
Conclusions:
The data show that SPF values above 50 and up to at least 90 can be measured by multiple laboratories with accuracy and reproducibility.
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