Validity and sensitivity to change of laser Doppler imaging as a novel objective outcome measure for cutaneous lupus erythematosus

Abstract

ObjectivesThe objectives of this study were to assess the reliability of a novel objective outcome measure, laser Doppler imaging (LDI), its validity against skin biopsy histology and other clinical instruments, including localized cutaneous lupus disease area and severity index (L-CLASI) and visual analogue scale (VAS) score of photographs, and its responsiveness to clinical change with therapy.MethodsA prospective observational cohort study was conducted in 30 patients with active cutaneous lupus erythematosus (CLE). At baseline and 3 months, disease activity was assessed using L-CLASI and a high resolution LDI system by two assessors. Skin biopsy was scored as 0 = non-active, 1 = mild activity and 2 = active. Photographs were assessed by two clinicians using 100 mm VAS. Inter-rater reliability was analyzed using Bland–Altman limits of agreement. Correlation between histology and LDI, L-CLASI and VAS and sensitivity to change of LDI with physician subjective assessment of change (PSAC) at 3 months were analyzed using Kendall’s tau-a.ResultsOf 30 patients with CLE, 28 (93%) were female, mean (SD) age 48.4 (11.5) y, 25 (83%) were Caucasians, 25 (83%) had concurrent systemic lupus erythematosus and 16 (53%) were smokers. CLE subtypes were acute = 9, subacute = 8 and chronic = 13. Inter-rater agreement for LDI was fair but for VAS score of photographs was poor. In 20 patients with biopsy, correlation with histology was better for LDI (tau-a = 0.53) than L-CLASI (tau-a = 0.26) (difference = 0.27; 90% CI 0.05–0.49) or VAS score of photographs (tau-a = 0.17) (difference = 0.36; 90% CI 0.04–0.68). There was a moderate correlation between PSAC score and change in LDI (tau-a = 0.56; 90% CI 0.38–0.74; p < 0.001, n = 15).ConclusionLDI provides a reliable, valid and responsive quantitative measure of inflammation in CLE. It has a better correlation with histology compared to clinical instruments. LDI provides an objective outcome measure for clinical trials.