Validity of additional use of optical immunofluorescence imaging technique (Xiralite®) in detection of active psoriatic arthritis and measurement of disease activity in patients with psoriasis and psoriatic arthritis

Psoriatic arthritis (PsA) is a common chronic inflammatory joint disorder that is closely associated with psoriatic skin disease. Mostly, musculoskeletal involvement occurs after skin manifestations [1]. In early manifestations of PsA, changes in synovial vascularisation combined with increased expression of pro-angiotic factors appear [2]. Therefore, imaging principles for detection of changes in vascularisation can be used for early detection of joint disease and monitoring of disease activity. Xiralite® is a new fluorescence optical imaging device licensed for the detection of changes in microvascularisation of the hands. The method is tailored to the contrast agent ICG (indocyanine green; e.g. ICG-Pulsion®), which is approved in Europe as an agent for imaging diagnostics of microcirculation. After intravenous contrast administration, altered microcirculation of joints, tendons, bones and ligaments will be displayed due to an increased signal of the contrast agent [3]. Validity and sensitivity of Xiralite® will be examined in two differ¬ent scenarios: Validity and sensitivity of Xiralite® in early detection of musculoskeletal involvement will be observed in patients with psoriasis having risk for development of musculoskeletal disease (XCITING study). Therefore, Xiralite® imaging will be compared to clinical examination and ultrasound. In a second project, changes in disease activity will be measured by Xiralite and correlated to clinical examination/ultrasound in a homogeneous patient-group with a standardized treatment regimen with Etanercept (XPLORE study). Both projects will be conducted at 12 centres in Germany. The enrolment period has recently started.