Background In rheumatoid arthritis (RA), treat-to-target strategies require instruments for valid detection of joint inflammation. With the use of imaging modalities such as ultrasonography (US) and magnetic resonance imaging (MRI), it has been shown that signs of joint inflammation are present in many patients in clinical remission. Consequently, these imaging modalities are used increasingly in clinical practice. In contrast to MRI and US, optical spectral transmission measurements (OST) are non-invasive and operator independent. Findings of OST of single joints have been shown to correlate with clinical examination.¹ Recently, a multi-joint device (Full Hand Proto (FHP)) has been developed.

Objectives In this study, an algorithm for prediction of the level of joint inflammation from OST measurements was developed and internally validated. Further, it was tested whether the FHP is able to diagnose subclinical joint inflammation as detected by US and MRI in patients with DAS₂₈ remission.

Methods In 59 patients with RA (20 with DAS₂₈ < 2.6, 26 with 2.6 ≥ DAS₂₈ ≤5.1 and 13 with DAS₂₈> 5.1) and 10 patients with arthralgia, OST, clinical examination, Disease Activity Score 28 (DAS₂₈), and US were performed. Additionally, MRI was performed in patients with DAS₂₈<2.6 in order to detect subclinical inflammation. The FHP measures OST at two wavelengths of joints of the hands and wrists before, during and after inflation of a pressure cuff positioned at the forearm of a test subject. Sixteen parameters describe the response curve at a single joint. Using regression analyses with bootstrapping, an algorithm was created to translate inflammation-dependent intersubject variance of the response curve into an absolute number per joint. US was used as reference for the detection of synovitis, which was defined as gray-scale score > 1 and/or power Doppler score > 0.

Results At the joint level, there was a good agreement of the FHP with US in PIP-joints (Area under the receiver-operating curve (AUC) of 0.83) and MCP-joints (AUC 0.78) and moderate agreement on wrist-level (AUC 0.61). At the patient level, the FHP correlated with clinical examination (DAS₂₈ r=0.41), and US (r=0.63). In patients with RA, median FHP was different between patients with and without ACR/EULAR remission (4.3 (2.6-4.4) vs 5.3 (4.1-7.4) (median (IQR), p=0.02) and also with respect to DAS₂₈ remission or not (4.5 (3.5-5.5) vs 6.3 (4.2-9.0), p=0.01). FHP predicted the absence of inflammation on US (AUC 0.79) and MRI (AUC 0.79). There was also correlation between subclincal inflammation detected on MRI and OST (RAMRIS synovitis r=0.53).

Conclusions The measurement of optical spectral transmission by the Full Hand Proto is a new and useful imaging modality in RA. There was a good agreement with US, and the Full Hand Proto was also able to detect subclinical joint inflammation on US and MRI.

References

1. Meier AJL et al. Potential of optical spectral transmission measurements for joint inflammation measurements in rheumatoid arthritis patients. J Biomed Opt 2012, 17 081420-1 - 081420-6

References

Disclosure of Interest M. van Onna: None Declared, D. F. Ten Cate: None Declared, K. L. Tsoi: None Declared, A. J. L. Meier: None Declared, J. W. G. Jacobs: None Declared, A. A. A. Westgeest: None Declared, P. B. L. Meijer Shareholder of: Hemics, Employee of: Hemics, M. C. van Beek Shareholder of: Hemics, Employee of: Hemics, W. H. J. Rensen Shareholder of: Hemics, Employee of: Hemics, J. W. J. Bijlsma: None Declared