Maxime Verhoeven

210 Chapter 11 measurement is widely applied in the Netherlands at out-patient-clinic visits. This could have favoured our study results regarding DAS28, but not regarding DAS-OST. The results of the OST-score only apply utilisation of the HandScan in the setting of this study, e.g., categorizing disease as inactive or active. Strength of our study is the relative large sample size of 1505 unique RA patients, with limited uninterpretable data. Conclusion Compared to DAS28, DAS-OST classified RA statistically significantly less well as active versus inactive, when using the clinical classification as reference standard, but it could be used in a strategy to limit outpatients’ visits to the rheumatologist. The discriminative ability of OST-score alone was negligible in this setting. REFERENCES 1. Smolen, J. S. et al. EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs: 2019 update. Ann. Rheum. Dis. 79 , 685–699 (2020). 2. Felson, D. T. et al. American College of Rheumatology/European League Against Rheumatism provisional definition of remission in rheumatoid arthritis for clinical trials. Arthritis Rheum. 63 , 573–586 (2011). 3. Jacobs, J. W. G., ten Cate, D. F. & van Laar, J. M. Monitoring of rheumatoid arthritis disease activity in individual patients: still a hurdle when implementing the treat-to-target principle in daily clinical practice. Rheumatology 54 , 959–961 (2015). 4. Grunke, M. et al. Standardization of joint examination technique leads to a significant decrease in variability among different examiners. J. Rheumatol. 37 , 860–864 (2010). 5. Scott, D. L. &Houssien, D. A. Joint assessment in rheumatoid arthritis. Br. J. Rheumatol. 35 , 14–18 (1996). 6. Porter, D. et al. DAS28 and rheumatoid arthritis: the need for standardization. Musculoskeletal Care 9 , 222–227 (2011). 7. Besselink, N. J. et al. Novel optical spectral transmission (OST)-guided versus conventionally disease activity-guided treatment: study protocol of a randomized clinical trial on guidance of a treat-to-target strategy for early rheumatoid arthritis. Trials 20 , 226 (2019). 8. Verhoeven, M. M. A. et al. Development and validation of rheumatoid arthritis disease activity indices including HandScan (optical spectral transmission) scores. Revision submitted to Arthritis Car Res. 9. Burmester, G. R. & Pope, J. E. Novel treatment strategies in rheumatoid arthritis. Lancet 389 , 2338–2348 (2017). 10. Wongpakaran, N., Wongpakaran, T., Wedding, D. & Gwet, K. L. A comparison of Cohen’s Kappa and Gwet’s AC1 when calculating inter-rater reliability coefficients: a study conducted with personality disorder samples. BMC Med. Res. Methodol. 13 , 61 (2013). 11. Verhoeven, M. M. A. et al. Utility of the HandScan in monitoring disease activity and prediction of clinical response in rheumatoid arthritis patients. In press, Rheumatology Advances in Practice January 2021. 12. Triantafyllias, K., Heller, C., de Blasi, M., Galle, P. & Schwarting, A. Diagnostic value of optical spectral transmission in rheumatoid arthritis: associations with clinical characteristics and comparison with joint ultrasonography. J. Rheumatol. 47 , 1314–1322 (2020).