Reliability and reproducibility of the Fitzpatrick phototype scale for skin sensitivity to ultraviolet light

Abstract

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Introduction. The Fitzpatrick phototype scale has been used to determine skin sensitivity to ultraviolet light. The reliability of this scale in estimating sensitivity permits risk evaluation of skin cancer based on phototype.

Objective. Reliability and changes in intra and inter-observer concordance was determined for the Fitzpatrick phototype scale after the assessment methods for establishing the phototype were standardized.

Materials and methods. An analytical study of intra and inter-observer concordance was performed. The Fitzpatrick phototype scale was standardized using focus group methodology. To determine intra and inter-observer agreement, the weighted kappa statistical method was applied. The standardization effect was measured using the equal kappa contrast hypothesis and Wald test for dependent measurements. The phototype scale was applied to 155 patients over 15 years of age who were assessed four times by two independent observers. The sample was drawn from patients of the Centro Dermatológico Federico Lleras Acosta.

Results. During the pre-standardization phase, the baseline and six-week inter-observer weighted kappa were 0.31 and 0.40, respectively. The intra-observer kappa values for observers A and B were 0.47 and 0.51, respectively. After the standardization process, the baseline and six-week inter-observer weighted kappa values were 0.77, and 0.82, respectively. Intra-observer kappa coefficients for observers A and B were 0.78 and 0.82. Statistically significant differences were found between coefficients before and after standardization (p<0.001) in all comparisons.

Conclusion. Following a standardization exercise, the Fitzpatrick phototype scale yielded reliable, reproducible and consistent results.