Abstract
Background:Valid assessment of disease activity leads to improvement of long-term outcomes in patients with inflammatory arthritis (1). Optical spectral transmission (OST) is a modern diagnostic tool able to assess the blood-specific absorption of light transmitted through a tissue, promising quantification of inflammation in the finger and wrist joints of patients with rheumatoid arthritis (RA) (commercial device: HandScan – Demcon/Hemics, The Netherlands) (2). Even though an increasing number of studies have evaluated diagnostic value of this new technology in RA patients (2,3), no data exist regarding psoriatic arthritis (PsA).Objectives:To examine for the first time the diagnostic value of OST in detecting inflammation in patients with PsA and to evaluate its relationship with disease activity markers and various epidemiological and anthropometric patient characteristics.Methods:OST-Measurements were performed in a group of PsA patients and a group of healthy controls. The difference between OST in the two groups was statistically examined and relationships of OST with clinical (tender / swollen joint counts, disease activity on a visual analogue scale) and serological disease activity markers were evaluated. Moreover, joint ultrasound (US) examinations were performed in a subgroup of PsA patients and OST associations with a Power Doppler- and a Grey Scale-US score were examined. Finally, relationships of OST with various anthropometric and epidemiologic parameters (BMI, hand-size, gender, age) were assessed.Results:We recruited 49 PsA patients [65.3% female; mean age 53.3 years (± 11.8 SD)] and 114 control subjects [77.2% female; mean age 46 years (± 12.8 SD)]. OST was statistically significantly higher in the patient group, compared to the control group [14.95 (12.04 - 17.18, IQR) vs. 10.31 (7.84 – 13.79, IQR); p<0.001]. OST correlated moderately-strongly with both examined US scores (Power Doppler-score: r = 0.5; p = 0.026 and Grey Scale-score: r = 0.52; p = 0.028). Moreover, OST showed a moderate, statistically significant association with C-reactive protein (CRP) (r = 0,298; p = 0,037). Finally, males had significantly higher OST values than females and OST associated moderately-weakly with body mass index (BMI) in the control group (rho = 0.24; p< 0.001).Conclusion:This is the first report of a possible diagnostic value of OST in patients with PsA. OST correlated with ultrasound and serological activity markers and may thus prove to be a useful tool of disease activity assessment, next to well established diagnostic modalities, such as the joint US. Correlations of OST with patient characteristics implicate the need to take also anthropometric and epidemiological patient characteristics into account when interprenting OST results in order to avoid confounding.
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