Comparison of a semiautomated hand-held device to test minimal erythema dose before narrowband ultraviolet B phototherapy with the conventional method using matched doses

Narrow-band phototherapy in the treatment of atopic dermatitis: mechanisms of action, methodology of implementation

Phototherapy is widely used to treat various chronic skin diseases. One of the most effective methods of treatment is narrow-band medium-wave ultraviolet radiation with a wavelength of 311 nm (UVB-311). UVB-311 is used for such immune-mediated diseases as atopic dermatitis, psoriasis, vitiligo, mycosis fungoides and others. Despite the fact that the method was developed more than 30 years ago, the exact mechanism of its therapeutic action remains insufficiently studied. To date, most of the effects of UVB-311 are explained by its effect on the immune cells of the skin. This review examines data on the effects on the main molecular targets, including T-lymphocytes, keratinocytes, Langerhans cells, cytokine profile, epidermal barrier proteins. Data on the features of the pathogenetic effect of UVB-311 on the immune mechanisms of pathogenesis in atopic dermatitis were obtained. The issues of dosing by determining the minimum erythemic dose (MED) or skin phototype, methodology of procedures are discussed. Prospects for further study of photobiological aspects of UVB-311 action are determined.

The erythema Q-score, an imaging biomarker for redness in skin inflammation

Physician rating of cutaneous erythema is central to clinical dermatological assessment as well as quantification of outcome measures in clinical trials in a number of dermatologic conditions. However, issues with inter‐rater reliability and variability in the setting of higher Fitzpatrick skin types make visual erythema assessment unreliable. We developed and validated a computer‐assisted image‐processing algorithm (EQscore) to reliably quantify erythema (across a range of skin types) in the dermatology clinical setting.

Our image processing algorithm evaluated erythema based upon green light suppression differentials between affected and unaffected skin. A group of four dermatologists used a 4‐point Likert scale as a human evaluation of similar erythematous patch tests. The algorithm and dermatologist scores were compared across 164 positive patch test reactions. The intra‐class correlation coefficient of groups and the correlation coefficient between groups were calculated. The EQscore was validated on and independent image set of psoriasis, minimal erythema dose testing and steroid‐induced blanching images. The reliability of the erythema quantification method produced an intra‐class correlation coefficient of 0.84 for the algorithm and 0.67 for dermatologists. The correlation coefficient between groups was 0.85. The EQscore demonstrated high agreement with clinical scoring and superior reliability compared with clinical scoring, avoiding the pitfalls of erythema underrating in the setting of pigmentation. The EQscore is easily accessible (http://lab.rockefeller.edu/krueger/EQscore), user‐friendly, and may allow dermatologists to more readily and accurately rate the severity of dermatological conditions and the response to therapeutic treatments.

Evaluation of the minimal erythema dose for UVB and UVA in context of skin phototype and nature of photodermatosis

BACKGROUND

Phototesting is part of the standard procedure for the evaluation of patients with photosensitivity disorders. The response of patients to targeted UVB or UVA radiation helps to find out more about the nature of photodermatosis. Nevertheless, there are no default values of the minimal erythema dose (MED).

METHODS

This study evaluated data of 203 patients (131 female, 72 male, mean age 52 years) who were referred for phototesting to the University Hospital Zurich between 2012 and 2017. We retrospectively analyzed the demographic data, medical history, skin phototype, reaction to UVB and UVA radiation, and, if present, the diagnosis of photodermatosis. In patients who did not develop erythema at the highest tested UV doses, the next logical increment was taken for analysis. In case of UVA, the two periphery doses could not be evaluated due to technical issues, so the closest reliable UVA doses were used.

RESULTS

The MED-UVB correlated with the skin type and increased with a higher phototype. No such correlation could be seen for MED-UVA. However, the MED-UVA was significantly reduced in patients with photodermatosis without significant differences between the subgroups of photodermatosis. More than half of the patients did not show a reduced MED despite a diagnosed photodermatosis.

CONCLUSION

We showed, how different skin types with and without photodermatosis react to UV radiation. Based on the results, we suggested threshold doses that can be chosen for phototesting, presented which doses can be considered pathologic and showed the probability of a pathologic MED in correlation with a diagnosed photodermatosis.