Wouter Harry Jacinth Rensen

Assessment of disease activity in patients with rheumatoid arthritis using optical spectral transmission measurements, a non-invasive imaging technique

Objectives In rheumatoid arthritis (RA), treat-to-target strategies require instruments for valid detection of joint inflammation. Therefore, imaging modalities are increasingly used in clinical practice. Optical spectral transmission (OST) measurements are non-invasive and fast and may therefore have benefits over existing imaging modalities. We tested whether OST could measure disease activity validly in patients with RA. Methods In 59 patients with RA and 10 patients with arthralgia, OST, joint counts, Disease Activity Score (DAS) 28 and ultrasonography (US) were performed. Additionally, MRI was performed in patients with DAS28<2.6. We developed and validated within the same cohort an algorithm for detection of joint inflammation by OST with US as reference. Results At the joint level, OST and US performed similarly inproximal interphalangeal-joints (area under the receiver-operating curve (AUC) of 0.79, p<0.0001) andmetacarpophalangeal joints (AUC 0.78, p<0.0001). Performance was less similar in wrists (AUC 0.62, p=0.006). On the patient level, OST correlated moderately with clinical examination (DAS28 r=0.42, p=0.001), and US scores (r=0.64, p<0.0001). Furthermore, in patients with subclinical and low disease activity, there was a correlation between OST and MRI synovitis score (RAMRIS (Rheumatoid Arthritis MRI Scoring) synovitis), r=0.52, p=0.005. Conclusions In this pilot study, OST performed moderately in the detection of joint inflammation in patients with RA. Further studies are needed to determine the diagnostic performance in a new cohort of patients with RA.

Potential of optical spectral transmission measurements for joint inflammation measurements in rheumatoid arthritis patients

Frequent monitoring of rheumatoid arthritis (RA) patients enables timely treatment adjustments and improved outcomes. Currently this is not feasible due to a shortage of rheumatologists. An optical spectral transmission device is presented for objective assessment of joint inflammation in RA patients, while improving diagnostic accuracy and clinical workflow. A cross-sectional, nonrandomized observational study was performed with this device. In the study, 77 proximal interphalangeal (PIP) joints in 67 patients have been analyzed. Inflammation of these PIP joints was also assessed by a rheumatologist with a score varying from 1 (not inflamed) to 5 (severely inflamed). Out of 77 measurements, 27 were performed in moderate to strongly inflamed PIP joints. Comparison between the clinical assessment and an optical measurement showed a correlation coefficient r=0.63, p<0.001, 95% CI [0.47, 0.75], and a ROC curve (AUC=0.88) that shows a relative good specificity and sensitivity. Optical spectral transmission measurements in a single joint correlate with clinical assessment of joint inflammation, and therefore might be useful in monitoring joint inflammation in RA patients.

Non-Invasive Blood Analysis Using Raman Spectroscopy

We have developed a non-invasive blood analysis method based on combined imaging and confocal Raman spectroscopy. With this technology, in-vivo Raman spectra can be obtained that resemble in-vitro spectra with respect to shape and intensity.