PIE's UV sensitivity system is based on similar principles to the Fitzpatrick skin type system but is divided into 10 stages. In this system, lower stages indicate higher sensitivity to UV light. For example, Stage 10 is highly sensitive to UV, similar to Fitzpatrick Type I, while Stage 1 is less sensitive, similar to Fitzpatrick Type VI. Thus, PIE's UV sensitivity classification follows the same basic principles as Fitzpatrick but with a more detailed scale for UV response evaluation.