Optical coherence tomography for patch test grading: A prospective study on its use for noninvasive diagnosis of allergic contact dermatitis.

BACKGROUND: The diagnosis of allergic contact dermatitis should be confirmed by skin patch tests. Distinguishing between irritant and allergic reactions is sometimes difficult. OBJECTIVES: To analyse the in vivo morphological changes in patch test reactions compared to healthy skin, and to detect subclinical changes in doubtful reactions using optical coherence tomography (OCT). To develop an OCT-based algorithm to support patch-test grading. METHODS: One hundred twenty-nine skin patch-test areas were scanned with OCT to evaluate the following features: architectural and vascular morphology, epidermal thickness, optical attenuation coefficient (AC), and blood flow at 0.1, 0.2, and 0.35 mm depth. RESULTS: Most common OCT features of acute contact allergic reactions in patch tests were spongiosis with microvesicles (94.8%), macrovesicles (60.3%), and coalescing vesicles (46.6%), the latter useful in differentiating acute allergic from irritant dermatitis (P-value < .05). Objective quantitative parameters correlated well with the severity grade: epidermal thickness due to spongiosis, AC (P-value < .05) and blood flow at 0.2 and 0.35 mm (P-value < .01). CONCLUSIONS: OCT as a noninvasive diagnostic tool, established for skin cancer diagnosis, is useful for evaluating contact allergic patch-test reactions. Not only morphological but also objective features such as blood flow and AC correlate with the reaction severity. Further studies are needed to explore the differences in irritant and allergic contact dermatitis.

Optoacoustic mesoscopy shows potential to increase accuracy of allergy patch testing.

BACKGROUND: Differentiation between irritant and allergic skin reactions in epicutaneous patch testing is based largely on subjective clinical criteria, with the risk of high intraobserver and interobserver variability. Novel dermatological imaging using optoacoustic mesoscopy allows quantitative three-dimensional assessment of microvascular biomarkers. OBJECTIVES: We investigated the potential of optoacoustic imaging to improve the precision of patch test evaluation. METHODS: Sixty-nine test reactions and 48 healthy skin sections in 52 patients with suspected type IV allergy were examined using raster-scan optoacoustic mesoscopy. RESULTS: We identified biomarkers from the optoacoustic images. Allergic reactions were associated with higher fragmentation of skin vasculature than irritant reactions (19.5 ± 9.7 vs 14.3 ± 3.7 fragments/100 pixels2 ; P < .05), as well as lower ratio of low- to high-frequency acoustic signals (1.6 ± 0.5 vs 2.0 ± 0.6, P < .05). Allergic reactions graded "++" showed higher vessel fragmentation than reactions graded "+" (25.4 ± 13.2 vs 17.1 ± 6.5 fragments/100 pixels2 ; P < .05). A linear model combining the biomarkers fragmentation and frequency ratio could differentiate allergic from irritant test reactions with an area under the receiving operator characteristic curve of 0.80 (95% confidence interval 0.64-0.91), reaching a sensitivity of 81% and specificity of 63%. CONCLUSIONS: Optoacoustic mesoscopy shows potential to help in differentiating between allergic and irritant test reactions based on novel biomarkers that may reflect vasodilation, vessel tortuosity, and edema.

Patch test reactions through the lens of dermoscopy: Further insights, particularly on weak allergic reactions.

BACKGROUND: Distinguishing weak allergic reactions from irritant patch test reactions may be difficult. OBJECTIVES: To describe the dermoscopic features of allergic reactions (especially weak allergic ones) and irritant patch test reactions, and to assess the suitability of dermoscopy in supporting differential diagnosis. METHODS: Eligible participants for this observational, cross-sectional study included consecutive adult outpatients patch tested during a 12-month period, who developed any skin reaction. Healthy volunteers were patch tested with sodium lauryl sulfate as irritant controls. At the 72-hour reading, patch test reactions were recorded both with a digital camera and a digital dermoscopic system. For each reaction, clinical and dermoscopic variables were separately assessed, scored, and then compared. RESULTS: Erythema, vessels, and vesiculation were constant dermoscopic features of allergic reactions (n = 173). In 46 weak (+) allergic reactions, dermoscopy showed (a) erythema (100%), (b) dense polymorphic vessels (100%), and (c) whitish vesicles (78.3%). Scores for vesicles and dotted vessels were significantly higher in weak allergic than in irritant reactions. Vesicles were identified as the chief dermoscopic parameter for correctly distinguishing weak allergic from irritant reactions. CONCLUSIONS: Dermoscopy can improve accuracy in the differential diagnosis between weak allergic and irritant patch test reactions.

In Vivo Reflectance Confocal Microscopy: Emerging Role in Noninvasive Diagnosis and Monitoring of Eczematous Dermatoses. / Microscopia confocal de reflectancia in vivo: papel emergente en el diagnóstico no invasivo, así como en el seguimiento de las dermatosis eccematosas.

Dermatologic diagnosis and monitoring have been dependent largely on visual grading. A skin biopsy is performed in case of diagnostic uncertainty, but can be traumatic, and results are delayed due to time for specimen transport and processing. Biopsies also destroy specimens, prohibiting lesion evolution monitoring. In vivo reflectance confocal microscopy (RCM) offers a diagnostic alternative to skin biopsy. RCM captures real-time, high-resolution images, and has been piloted for the evaluation of various dermatologic conditions. Identification of unique RCM features may distinguish dermatoses with similar clinical morphologies. Allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD) are diagnosed by patch testing that currently uses a subjective scoring system. RCM has increasingly been studied for early detection and severity grading of CD. Common RCM features shared by ACD and ICD are stratum corneum disruption, vesicle formation, exocytosis, spongiosis, and parakeratosis. Features unique to ACD are vasodilation, increased epidermal thickness, intercellular edema, and acanthosis. Features unique to ICD are detached corneocytes and targetoid keratinocytes. This review summarizes the use of RCM in evaluating contact eccematous conditions and aims to spark future research and interest in this promising tool.

Anti-inflammatory potency testing of topical corticosteroids and calcineurin inhibitors in human volunteers sensitized to diphenylcyclopropenone.

AIMS: To quantify the anti-inflammatory potency of topical corticosteroids and topical calcineurin inhibitors by measuring the contact allergic response to a diphenylcyclopropenone (DPCP) challenge in de novo sensitized human volunteers. METHODS: Two randomized, double-blind, vehicle-controlled studies were performed encompassing 76 volunteers: 29 in the first and 47 in the second study. Topical drugs were applied pre- and/or post-treatment in block designs. The compounds were tested simultaneously under occluded patch tests covering DPCP-induced dermatitis. Inhibitory responses were assessed by visual scoring and measurements of the oedema thickness with ultrasound. RESULTS: When applied both before and after the DPCP challenge, significant anti-inflammatory effects were seen in descending order for tacrolimus 0.1% ointment, clobetasol propionate ointment, betamethasone valerate ointment and hydrocortisone butyrate ointment, while pimecrolimus cream, hydrocortisone ointment and vehicles had no significant effect. Only tacrolimus ointment (P < 0.01) demonstrated a consistent significant pre-treatment inhibitory effect compared with an untreated DPCP control. CONCLUSIONS: This human testing method in which the inflammation of experimentally induced allergic patch test reactions is quantified by objective measurement allows an analysis of the anti-inflammatory potency of not only topical corticosteroids, but also of drugs that have no effect on vasoconstriction. The method allowed comparison of the potencies of four topical corticosteroids and two calcineurin inhibitors.

Different concentrations and volumes of p-phenylenediamine in pet. (equivalent doses) are associated with similar patch test outcomes: a pilot study.

BACKGROUND: Concern about causing active sensitization when patch testing is performed with p-phenylenediamine (PPD) 1% pet. has led to a recommendation to use PPD 0.3% pet. as a potentially safer preparation. However, the dose per area of allergen delivered, and hence the risk of active sensitization, depend on the amount dispensed into the patch test chamber, which can vary widely. OBJECTIVE: To evaluate whether patch testing with equivalent doses of different concentrations of PPD in pet. is associated with similar outcomes. METHODS: Seventeen known PPD-sensitive subjects were patch tested with different volumes and concentrations of PPD in pet. that deliver the same allergen dose per unit area (6 mg of PPD 1% pet. and 20 mg of PPD 0.3% pet. in Finn Chambers®, both equivalent to ∼ 0.09 mg/cm2 ). RESULTS: Eleven patients (65%) had positive reactions to both doses; 4 patients (24%) had negative results [percentage agreement of 88% (15/17)]. One patient each had a positive reaction to only one dose. CONCLUSIONS: The 88% concordance suggests that dose per unit area is more important in determining reactions to allergens than the excipient volume dispensed. Patch testing with a smaller volume of 1% PPD may be a reasonable alternative to testing with 20 mg of 0.3% PPD.

Utility of Store and Forward Teledermatology for Skin Patch Test Readings.

BACKGROUND: Teledermatology (TD) is the use of imaging technology to provide dermatology services at a distance. To date, studies assessing its application for grading skin patch test reactions have been lacking. OBJECTIVES: The aim was to compare conventional, in-person (IP) grading of skin patch test reactions with store-forward TD. METHODS: Patients undergoing patch testing to the North American Contact Dermatitis Group (NACDG) screening series were invited to participate in this repeated-measures study. Photographs of the NACDG screening series patch sites were obtained at 2 time points (48-hour and final readings). Teledermatology assessments were completed by the same staff dermatologist who performed the IP readings; 48-hour and final TD photographs were viewed at weeks 4 and 8 after the IP encounter, respectively, to prevent recall bias. Staff dermatologists were blinded to IP grading results. The main outcome was percent agreement. Eight categories of agreement were created according to possible pairings of TD and IP reading results. Three final outcome groups of "success," "indeterminate," and "failure" were defined based on clinical significance. RESULTS: One hundred one participants completed the study. There were 7070 comparison points between IP and TD final readings. Excluding negative/negative agreement, there was "success" of TD in 54% of final readings. "Indeterminate" agreement with possible clinical significance was present in 40% of final readings. There was "failure" (definite clinical significance) in 6% of final readings. CONCLUSIONS: Teledermatology may be a viable option for grading skin patch test reactions, particularly for clinicians who perform limited patch testing. However, a clinically significant "failure" rate of 6% and practical barriers to TD implementation may preclude its widespread use for skin patch testing in tertiary referral centers where large numbers of patches are tested per patient.

Quantitative ultrasonic methods for characterization of skin lesions in vivo.

Quantitative ultrasonic methods were studied for characterizing skin lesions in vivo using contact dermatitis as an example. The parameters studied include skin thickness, echogenicity, attenuation coefficient slope and parameters related to echo statistics (signal-to-noise ratio and shape parameters of Weibull, K and generalized gamma distributions). Data were collected using a high-frequency ultrasound (US) system (center frequency = 33 MHz). To compensate for depth-dependent diffraction effects, correction curves as a function of the distance between the transducer and the tissue were first empirically obtained. Diffraction-corrected quantitative parameters were then compared between healthy and affected skin of volunteers, who underwent patch testing for allergic and irritant contact dermatitis. A significant increase in skin thickness, decrease in echogenicity of the upper dermis and decrease in attenuation coefficient slope were found at the affected sites compared to those of healthy skin. However, no differences in parameters related to the echo statistics of the mid-dermis were found. These results indicate that a combination of quantitative ultrasonic parameters have the potential for extracting information for characterizing skin conditions.

Parallel intraindividual evaluation of the vasoconstrictory action and the anti-allergic activity of topical corticosteroids.

The human skin blanching assay is a well established method for ranking the efficacy of corticosteroids after epicutaneous application. Vasoconstriction is a pharmacological activity, which correlates well with the clinical efficacy, the intensity of skin blanching after a single application under occlusion corresponding, generally, to the clinical efficacy after repeated application without occlusion. However, in studies dealing with the comparison between the vasoconstriction assay and the evaluation of the clinical effects on inflammatory skin diseases, some exceptions to this correlation have been reported. Therefore, in a pre-clinical phase, it would be useful to combine the blanching assay with at least one anti-inflammatory assay. In the present study the blanching assay and the allergic contact dermatitis inhibition test were performed in parallel, in order to compare the two testing procedures in the same group of subjects, utilizing standardized study designs supported by objective means of evaluation. Three commercial preparations of corticosteroids containing clobetasol propionate (CP), clobetasone butyrate (CB) and hydrocortisone acetate (HA), respectively, were employed both to treat nickel-induced positive patch test responses on the volar forearms, and to perform a vasoconstrictor assay on normal forearm skin in 16 nickel-sensitized healthy volunteers. For evaluating skin blanching, we employed colorimetric measurements, whereas for the quantitative determination of the inhibition of the intensity of allergic patch test reactions, 20 MHz B-scanning supported by image analysis was used. Both colorimetric and echogenicity values enabled us to distinguish between the three corticosteroids (at the 17 h evaluation and the 64 h assessment, respectively). A fair correlation was noted between colorimetric and echogenicity values. Both testing procedures ranked the three corticosteroids in the expected order. Corticosteroid preparations should be compared using methods which allow different effects to be simultaneously monitored, without involving a high number of patients. We are proposing this double procedure for the parallel intraindividual evaluation of the vasoconstrictory action and the anti-allergic activity of topical steroids.

Inhibition of elicitation of contact dermatitis in humans by mometasone furoate: evaluation by means of 20-MHz B scanning associated with image analysis.

BACKGROUND: Mometasone furoate (MF) is a new strongly lipophilic steroid which has an anti-inflammatory effect as evaluated by in vivo and in vitro studies. OBJECTIVE: The objective of the present study was to investigate the degree of inhibition of experimental allergic contact dermatitis induced by the treatment with MF. METHODS: The therapeutic effect was evaluated by an echographic method associated with image analysis. MF activity was compared to that of hydrocortisone acetate 0.5% (Cortaid Cream, Lachifarma), clobetasone butyrate 0.05% (Eumovate Cream, Glaxo) and clobetasol propionate 0.05% (Clobesol Cream, Glaxo), classified respectively as weak, moderately potent and very potent steroids. RESULTS: The different corticosteroid formulations employed for inhibiting experimentally induced contact dermatitis reflect the expected rank order of efficacy. CONCLUSION: MF behaves like clobetasol butyrate ranking as a moderately potent corticosteroid.

Two-dimensional blood flow determinations in allergic reactions using laser Doppler scanning.

The new technique of laser Doppler scanning (LDS) provides a 2-dimensional pattern of cutaneous microcirculation, which offers a visual image and can quantify the intensity and expansion of perfusion. With the help of this technique, we examined the microcirculatory pattern of Type IV reactions to recall antigens, which were applied using a test stamp (Multitest Merieux). The measurements were performed before application of the test stamp as well as 10 min, 24, 48 and 72 h afterwards. The inflammatory hyperemia was evaluated using LDS and unidimensional laser Doppler fluxmetry. The diameter of the inflammatory infiltrate was quantified by means of palpation, the thickness by means of high-resolution 20 MHz sonography. The clinically visible erythema was measured planimetrically. An unspecific hyperemia resulting from the trauma of the stamp revealed no evident infiltrate under sonography 10 min after the test application. Depending of the individual reaction, the mean flux and the expansion of the hyperemia were at their peak after 48 h. The flux values were at a maximum in the center of the inflammatory reaction and dropped continuously toward the periphery. The area of the hyperemia seen in the LDS image was significantly larger than the expansion of the erythema measured planimetrically, but there was a significant correlation. The perfusion correlated significantly with the infiltration diameter (24 h, 48 h, 72 h) and the infiltration thickness 48 h after testing. All in all, it was possible to measure directly and without touching the skin and to quantify a subclinical pattern of skin perfusion as a response to and inflammatory reaction on a 2-dimensional display.

Reactivity to nickel sulfate at sodium lauryl sulfate pretreated skin sites is higher in atopics: an echographic evaluation by means of image analysis performed on 20 MHz B-scan recordings.

The aim of this study was to establish an objectively assessable procedure simulating simultaneous exposure to irritants and allergens in domestic and occupational environments, in order to evaluate differences in the reactivity to the combination of these substances in atopic and non-atopic nickel-sensitized subjects. Thirty-four nickel-sensitive patients, 20 of whom were affected by atopic dermatitis, underwent four patch tests with NiSO4 0.05% aq. on two adjacent sites of both volar forearms, with a 24-h application time. Two of the test sites were treated with sodium lauryl sulfate (SLS) 5% for 30 min, before application of the nickel sulfate preparation. Echographic recordings were performed by a 20-MHz B-scanner and processed by an image analysis program, providing a numerical representation of the picture data, based on the attribution of fictional values to the amplitudes of the echoes. The dermal inflammatory reaction was quantified by an amplitude band, marking the hypo-reflecting part of the dermis, whereas epidermal damage was assessed by a band highlighting the entrance echo. Pre-treatment with SLS of the skin area where nickel sulfate was subsequently applied greatly enhanced the allergic response at 24 and 72 h, both in subjects with atopic dermatitis and in subjects with allergic contact dermatitis. However, in atopics, the increase in the allergic reactivity after irritation of the skin was more pronounced both by clinical and by echographic evaluation. These observations stress the importance of the concurrent action of irritants and allergens in maintaining the dermatitis in atopics.