Assessment of the Activity of Tacalcitol on Psoriatic Plaques by Means of Colorimetry and High-Frequency Ultrasound: A Double-Blind Intrasubject Half-Side Right-Left Comparison with Betamethasone Valerate and Placebo

The aim of our study was to further investigate and to objectively assess the effects of tacalcitol on psoriasis by means of double-blind comparisons with placebo and betamethasone valerate, documented by instrumental evaluation. The study was conducted as intrasubject half-side right-left comparisons. Twelve subjects entered a double-blind placebo-controlled treatment (tacalcitol/placebo group), whereas 14 subjects received double-blind medication with tacalcitol/betamethasone valerate. Medications were applied once daily without occlusion to affected skin areas. Instrumental evaluations were carried out by means of a colorimeter and a 20-MHz B scanner. The colour co-ordinate a*, representing the colour range from green (-) to red (+), was used for assessing erythema. B scan images were processed according to segmentation procedures. A 0-10 interval, marking the hyporeflecting dermal areas, was used for assessing oedema and inflammatory infiltration at psoriatic plaque sites. Twenty-two patients (11 of the tacalcitol/betamethasone group and 11 of the tacalcitol/ placebo group) completed the treatment period. Mean a* values showed an increase in the tacalcitol/betamethasone group after the first week of therapy on both sides, followed by a slight decrease, the values of which did not reach statistical relevance for either treatment. The decrease observed at tacalcitol-treated sites in patients of the tacalcitol/placebo group was not significant either with respect to baseline values during the first weeks of therapy. The extension of 0-10 dermal areas decreased both in betamethasone- and tacalcitol-treated areas in both patient groups. No significant differences were noticeable between the two treatments at all assessment points, although both by clinical and echographic evaluation a more pronounced decrease in clinical scores and in echogenicity values was observable at betamethasone-valerate-treated sites, especially at weeks 6 and 8. According to our data, assessment of erythema does not always represent a valid method for monitoring the response to therapy in psoriatic patients. In fact, modifications of a* values did not allow a distinction between different treatments, whereas processing of echographic images by the 0-10 segmentation enabled tacalcitol to be classified as a topical drug, the activity of which approaches that of a potent steroid.