Digitala Vetenskapliga Arkivet

In a previous publication from our group, phototesting based on a single exposure to a divergent UVB beam with radially decreasing irradiance values was suggested. The aim of the present study was to evaluate technical, practical and biological aspects of the suggested method in normal subjects. Twenty healthy volunteers were provoked on the back with both a collimated beam (four fixed doses, in circular areas with a diameter of 1.5 cm) and the divergent beam (a continuous, radially attenuating dose spectrum covering an area with a diameter of 4.5 cm). Eleven of the subjects were subjected to double provocation with the divergent beam. Assessment was carried out at 6 and 24 h after exposure by measuring the diameter of the reactions both visually and by mapping the skin blood flow change with laser Doppler perfusion imaging (LDPI). Minimal erythemal dose (MED) was determined for both the collimated and the divergent provocation. The reaction diameters were used to decide MED by combination to a mm for mm mapped dose spectrum of the divergent beam profile. Dose-response curves were plotted using the quantitative response data of the LDPI-images against the corresponding dosimetry data. No systematic difference could be proven between LDPI and visual diameters and a 95% confidence interval for the mean difference was calculated to (-0.8, 2.0). Slightly greater diameters were found at the visual assessment performed at 6 h compared to 24 h (95% confidence interval (-0.1, 2.8)). Double provocation showed a good reproducibility both for the visual and the LDPI assessment (P<0.05). The divergent beam provocation allowed a more detailed discrimination of MED compared to the collimated beam provocation. The MED values determined with the divergent beam were, however, generally higher, especially in the lower range of MED values. Technical factors related to the beam divergence and the correct measurement of erythemal effective irradiance are believed to be the explanation for this phenomenon, which is thus correctable. In conclusion, the results from this study support our belief that the phototesting protocol based on a divergent beam constitutes a good opportunity for improved phototesting, since MED and dose-response characteristics may be extracted in more detail from a single UV exposure.

Background: In both clinical and experimental phototesting, naked eye assessment of erythema has been the main assessment parameter. As with all subjective assessment, variability in recorded results due to variable circumstances around the performance and reading of tests influences reliability and utility of data whether they be interpreted for an individual patient or for a group of research subjects.

Methods: In the present study, variability in the reporting of diameter of ultraviolet B (UVB) erythema has been studied. The erythematous reactions were assessed by the naked eye and with the help of a millimetre-graded ruler by a group of dermatologists and dermatological trainees. Reaction size, objectively quantified by means of laser Doppler perfusion imaging (LDPI) using thresholding of the reaction perfusion, and known size of UVB provocation were used as yardsticks in order to quantify this variability.

Results: Agreement between observers, against known size, was excellent for reactions with a sharp border, but for reactions with a diffuse or indistinct border there was a substantial inter-observer variability. This was also true for the comparison between naked-eye reading and LDPI assessment of the reaction size.

Conclusion: It is concluded that if naked-eye readings are to be the outcome measurement, then provocations/protocols producing distinct borders are an advantage. If borders between provoked and unprovoked skin can be expected to be diffuse, i.e. part of a continuum of response, the use of objective, bioengineering techniques such as LDPI is required. Quantitative methods are also the basis for more detailed presentation and interpretation of test results including information on dose response above the minimal erythema dose.

Background: Phototesting based on a single exposure to a divergent ultraviolet B (UVB) beam with radially decreasing UVB doses can be used to determine an individual's minimal erythema dose (MED). Laser Doppler perfusion imaging (LDPI) data can be combined with dosimetry data to produce objective dose–response plots in addition to the MED. The aim of this study was to investigate whether the divergent beam protocol could be used to demonstrate and quantify the anti-inflammatory effects of clobetasol diproprionate (Dermovate^®), pharmaceutical-grade acetone and a gel vehicle, applied after skin provocation by UVB.

Method: Sixteen Caucasian subjects were illuminated with the divergent beam on three areas close together on the left side of their upper backs. Two of the provoked areas on each subject were treated with acetone, gel vehicle or Dermovate^®, and one area was left untreated as a control. Skin blood perfusion was assessed 6 and 24 h after UVB illumination using LDPI. The reaction diameter, the mean perfusion, and the average dose–response plots for each group and treatment were extracted from the LDPI data.

Results: Application of the topical steroid clobetasol diproprionate after UVB provocation markedly decreased the inflammatory response. Acetone and the gel vehicle also showed mild anti-inflammmatory effects in two of the parameters but not for the mean perfusion response. The mean diameter differences between controls and treated reactions had predominantly positive 99% confidence intervals. Analysis of the dose–response data at doses higher than the MED showed a linear relationship (0.89≤R²≤0.98) for all reactions but with lower gradients in treated reactions, mostly marked for clobetasol diproprionate.

Conclusions:  The divergent beam protocol can be used to demonstrate and quantify the effects of topical agents on the UVB reaction, in terms of reaction diameter, mean perfusion and changes in dose–response characteristics. The dose–response approach seems to be applicable even in diagnostic testing of an individual patient's response to UVB.

Background/objective: The high skin cancer incidence in western society, and its known association with sun exposure habits, makes the area an important target for prevention. We investigated, in a primary healthcare setting, differentiated levels of prevention efforts directed at the propensity of the patient to change his/her sun habits, sun protection behaviour, and attitudes, after information intervention. Additionally, the impact of the performance of a phototest to determine individual sun sensitivity was evaluated. Methods: 308 patients visiting a primary healthcare centre in southern Sweden completed a questionnaire concerning sun habits, sun protection behaviour, and attitudes, and were randomized into one of three groups, representing increasing levels of prevention effort in terms of resources. Feedback on their questionnaire and general preventive sun protection advice was given, in the first group by means of a letter, and in the second and third groups by a doctor's consultation. Group 3 also underwent a phototest, with a self-reading assessment and a written follow-up of the phototest result. Change of sun habits, behaviour, and attitudes, based on the Transtheoretical Model of Behaviour Change and on Likert scale scorings, was evaluated after 6 months, by a repeated questionnaire. Results: Prevention mediated by a doctor's consultation had a clearly better impact on the subjects. The addition of a phototest did not further reinforce this effect in the group as a whole, but it did for a subgroup of individuals with high ultraviolet (UV) sensitivity, as determined by the phototest itself, suggesting that this might actually be a tool to improve outcome in this high-risk group. Conclusion: A personal doctor's consultation is a valuable tool in the effective delivery of preventive information in the general practice setting. In individuals with high UV-sensitivity and thus high risk for skin cancer the performance of a photo-test reinforces a positive outcome in habits, behaviour and attitudes.