Determination of minimal erythema dose and anomalous reactions to UVA radiation by skin phototype.

BACKGROUND: Phototesting is a technique that assesses the skin's sensitivity to UV radiation by determining the smallest dose of radiation capable of inducing erythema (minimal erythema dose [MED]) and anomalous responses to UV-A radiation. No phototesting protocol guidelines have been published to date. METHODOLOGY: This was a multicenter prospective cohort study in which 232 healthy volunteers were recruited at 9 hospitals. Phototests were carried out with solar simulators or fluorescent broadband UV-B lamps. Each individual received a total of 5 or 6 incremental doses of erythemal radiation and 4 doses of UV-A radiation. The results were read at 24hours. RESULTS: At hospitals where solar simulators were used, the mean (SD) MED values were 23 (8), 28 (4), 35 (4), and 51 (6) mJ/cm(2) for skin phototypes i to iv, respectively. At hospitals where broadband UV-B lamps were used, these values were 28 (5), 32 (3), and 34 (5) mJ/cm(2) for phototypes ii to iv, respectively. MED values lower than 7, 19, 27, and 38 mJ/cm(2) obtained with solar simulators were considered to indicate a pathologic response for phototypes I to IV, respectively. MED values lower than 18, 24, and 24mJ/cm(2) obtained with broadband UV-B lamps were considered to indicate a pathologic response for phototypes ii to iv, respectively. No anomalous responses were observed at UV-A radiation doses of up to 20J/cm(2). CONCLUSIONS: Results were homogeneous across centers, making it possible to standardize diagnostic phototesting for the various skin phototypes and establish threshold doses that define anomalous responses to UV radiation.

An empirical model of erythemal ultraviolet radiation in the city of Valencia, Spain.

This paper presents an improved empirical model that predicts ultraviolet erythemal radiation (UVER) and considers all aspects of atmospheric conditions in Valencia, Spain. The analyzed model is a potential function whose dependent variable is UVER radiation and independent variables are the clearness index and slant ozone column. A potential regression function with all the information contributed a small coefficient of determination and one chose to use a regression potential-exponential mathematical form which improved the coefficient of similar determination. A study was carried out on the influence of season on the regression parameters. This was found to be considerable due to the clearness index. The convergence between the values calculated by the model and the experimental values was analyzed using the mean bias error (MBE) and mean absolute bias error (MABE) statistical parameters. The clearness index and ozone column intervals were analyzed and found to give an improved prediction of the UVER clearness index using regression analysis. Also, a sensitivity analysis was performed on the regression coefficients and parameters. It is important to study the effects of UVER radiation predicted by the model on human health or on agriculture crop growth and yield.