Baumann Skin Type Questionnaire (BSTQ): creation and validation of the Polish language version - part two.

Introduction: Skin type assessment is important because it is a guidance for specialists and consumers to select and recommend the most appropriate skin care products and protocols. One easy-to-administer instrument used for skin type classification is the Baumann Skin Type Questionnaire.

Aim: Translation and validation of the Polish version of the Baumann Skin Type Questionnaire (BSTQ) - pigmented or non-pigmented and wrinkled or tight skin.

Material and methods: Both forward and backward translation of the English version of the BSTQ was performed. The study was conducted on 103 individuals. The respondents completed the questionnaire twice, 1 day after the other. The subjects participated in practical classes of facial care cosmetology which allowed for conducting interviews and skin examinations by a cosmetology expert.

Results: The Polish version of the BSTQ demonstrated high test-retest reliability (reproducibility) in the dimension evaluating skin with or without hyperpigmentation as well as wrinkled or tight skin (ICC3 = 0.91; ICC3 = 0.97, respectively). Moreover, an excellent level of agreement between initial test and retest (pigmented vs. non-pigmented: AC1 = 1.00, 95% CI:1.00; wrinkled vs. tight: AC1 = 0.93, 95% CI:0.87-0.99). However, the Polish version of the BSTQ demonstrated a low internal consistency, corroborated by low Guttman's Lambda 6 reliability (pigmented vs. non-pigmented: α_raw = 0.55, α_std = 0.54, G6 = 0.63; retest: α_raw = 0.58, α_std = 0.54, G6 = 0.63; wrinkled vs. tight: α_raw = 0.33, α_std = 0.25, G6 = 0.47; retest: α_raw = 0.36, α_std = 0.33, G6 = 0.54).

Conclusions: The use of the BSTQ in assessing the skin for hyperpigmentation and age-related changes should be complemented by another diagnostic approach - clinical assessment before starting treatment or anti-aging interventions.