In Vivo reflectance confocal microscopy of cutaneous acute graft-versus-host disease: concordance with histopathology and interobserver reproducibility of a glossary with representative images.

BACKGROUND: The reliability to non-invasively identify features of inflammatory dermatoses by reflectance confocal microscopy (RCM) remains unknown. Lack of formal training among RCM readers can result in inconsistent assessments, limiting clinical utility. Specific consensus terminology with representative images is necessary to ensure consistent feature-level interpretation among RCM readers. OBJECTIVES: (1) Develop a glossary with representative images of RCM features of cutaneous acute graft-versus-host disease (aGVHD) for consistent interpretation among observers, (2) assess the interobserver reproducibility among RCM readers using the glossary, and (3) determine the concordance between RCM and histopathology for aGVHD features. METHODS: Through an iterative process of refinement and discussion among five international RCM experts, we developed a glossary with representative images of RCM features of aGVHD. From April to November 2018, patients suspected of aGVHD were imaged with RCM and subsequently biopsied. 17 lesions from 12 patients had clinically and pathologically confirmed cutaneous aGVHD. For each of these lesions, four dermatopathologists and four RCM readers independently evaluated the presence of aGVHD features in scanned histopathology slides and 1.5 × 1.5 mm RCM submosaics at 4 depths (blockstacks) respectively. RCM cases were adjudicated by a fifth RCM expert. Interobserver reproducibility was calculated by mean pairwise difference (U statistic). Concordance between modalities was determined by fraction of assignments with agreement. RESULTS: We present a glossary with representative images of 18 aGVHD features by RCM. The average interobserver reproducibility among RCM readers (75%, confidence interval, CI: 71-79%) did not differ significantly from dermatopathologists (80%, 76-85%). The concordance between RCM and histopathology was 59%. CONCLUSIONS: By using the glossary, the interobserver reproducibility among RCM readers was similar to the interobserver reproducibility among dermatopathologists. There was reasonable concordance between RCM and histopathology to visualize aGVHD features. The implementation of RCM can now be advanced in a variety of inflammatory conditions with a validated glossary and representative image set.

Comparison of single-spot technique and RGB imaging for erythema index estimation.

A commercially available point measurement device, the Mexameter(®), and an experimental RGB imaging prototype device were used for erythema index estimation of 50 rosacea patients by analysing the level of skin redness on the forehead, both cheeks and both sides of a nose. Results are compared with Clinician's Erythema Assessment (CEA) values given by two dermatologists. The Mexameter uses 568 nm and 660 nm LEDs and a photodetector for estimation of erythema index, while the used prototype device acquired RGB images at 460 nm, 530 nm and 665 nm LED illumination. Several erythema index estimation algorithms were compared to determine which one gives the best contrast between increased erythema and normal skin. The erythema index estimations and CEA values correlated much better for the RGB imaging data than for those obtained by the conventional Mexameter technique that is widely used by dermatologists and in clinical trials. In result, we propose an erythema index estimation approach that represents increased erythema with higher accuracy than other available methods.