AB1079 CORRELATION OF OPTICAL SPECTRAL TRANSMISSION IMAGING WITH ULTRASOUND AND DISEASE ACTIVITY IN RHEUMATOID ARTHRITIS PATIENTS

Abstract

Background:Optical spectral transmission imaging (OST) is a new imaging method that measures inflammation in the hands of rheumatoid arthritis (RA) patients. OST might be used to assess disease activity instead of disease activity score 28 (DAS28) or ultrasonography (US), with the advantage of OST that it is fast and not operator dependent. Detection of joint inflammation with OST and with US as reference, has provided varying outcomes with ROC AUCs ranging from 0.69-0.88 [1-3]. Further evaluation of the currently available OST device (HandScan) is needed in other RA cohorts.Objectives:To assess the correlation of OST measurement with US and disease activity, and to compare OST measurements of RA patients with healthy controls.Methods:OST was done in 24 consecutive RA patients with active disease and 37 age and sex matched healthy controls using the HandScan device from Hemics, the Netherlands. The HandScan calculates OST values for each bilateral wrist, MCP and PIP joint, ranging from 0 to 3. OST total score is then composed of the sum of the 22 OST joint scores and therefore ranges from 0 to 66. US was performed in the same joints as OST and semi-quantitatively scored on a scale of 0 to 3 for grey-scale (GS) synovitis and power Doppler (PD) signal individually. A separate total score for GS synovitis and PD was calculated by summation of the individual joint US scores. Joint scores (at joint level) and total scores (at patient level) were used in separate analyses. Additionally, we measured swollen joint count 28 (SJC28), tender joint count 28 (TJC28), DAS28, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). For all statistical analyses, the non-parametric variant was used.Results:Patient levelMedian OST total score of RA patients was 16.88 (IQR 12.68-19.72). This was significantly higher than healthy controls (OST total score 12.06, IQR 10.32-14.93; p=0.0002).OST total score of RA patients (patient level) did not significantly correlate with both US total scores (GS synovitis 0.37, p=0.08; PD 0.21, p=0.33), nor with disease activity parameters (DAS28 0.22, p=0.31; SJC28 0.32, p=0.12; TJC28 0.28, p=0.19; ESR -0.02, p=0.93; CRP 0.05, p=0.81).Joint levelAt joint level, there was a significant correlation for almost all joints with GS synovitis on US (table 2). For PD too few joints scored above 0 to allow for statistical comparisons, however for all joints median OST values were higher in PD positive joints than PD negative joints (differences in median OST values ranging from 0.2-0.5).Table 2.Correlation of individual joint OST values and GS synovitisGS synovitisSpearman rp-valueWrist0.360.02MCP10.270.06MCP20.440.002MCP30.400.005MCP40.270.07MCP50.390.006IP10.350.01PIP20.300.04PIP30.130.37PIP40.290.04PIP50.370.01Conclusion:OST total score was higher for RA than healthy controls. At patient level, OST total score did not correlate with other disease activity measures. At joint level, GS synovitis scores correlated with OST joint values for almost all joints. In addition, higher OST values were found in PD positive joints but frequency of PD positivity was too low to allow statistical comparisons. The results of this small cohort of new RA patients do not yet demonstrate additional value as compared to US and clinical examination to detection of joint inflammation at cross-sectional assessment, although fast and non-operator dependent OST assessment may also be weighed in further evaluation for clinical use.