Discussion
DIP joints, inflammation, arthritis, tenosynovitis, GSUS, RA, EULAR-OMERACT
INFLAMMATION, DISEASE, ARTHRITIS, TENOSYNOVITIS
Our data suggest that OST is a promising diagnostic tool with a possible utility in the follow-up of patients with RA. Moreover, we found an excellent diagnostic performance in the comparison between controls and patients and moderate-strong significant correlations between OST and several clinical and joint US activity markers.To our knowledge, this is the first study to examine the diagnostic value of OST in the follow-up of patients with active arthritis, taking as a reference the gold standard assessment method of joint US, which also allows the detection of subclinical disease activity.In the past, several studies, including those of our working group have shown that OST could be a promising diagnostic modality for the screening of arthritis patients, particularly when certain limiting parameters, such as OST confounding factors, are taken into account [In our study, we have followed a more targeted approach and have used joint-US as a diagnostic reference for OST. This gave us the possibility to assess inflammatory changes by OST of the exact same joints examined by US and thus obtain a more tailored evaluation of OST. Moreover, joint US gave us the opportunity to assess subclinical disease activity, which can predict relapse after premature withdrawal of anti-inflammatory therapy and is thus of higher diagnostic value compared to clinical examination [This finding is important, given the fact that valid tools of arthritis follow-up assessments are greatly needed in the field of Rheumatology. As well-known, a tight clinical control strategy associates with a longer activity suppression and an improved overall prognosis [On the other hand, US can be time-costly, is often performed only by physicians, and is additionally examiner-dependent. By having a tool with similar diagnostic value to US without the aforementioned disadvantages, everyday rheumatology practice could be eased.Interestingly enough, the distribution of ΔOST was similar to the distribution of ΔGSUS of only the MCP and PIP joints and not the wristsROC analyses showed an excellent performance of OST in distinguishing arthritis patients from controls at both examination time-points. In fact, AUC, sensitivity, and specificity values were higher compared to our previous study [This study has some limitations. OST measures inflammation only in the wrist, MCP, and PIP joints. Thus, the inflammatory activity of the DIP could not be assessed by OST. For that reason, we have not included any US values of the DIP joints in our assessed PDUS and GSUS scores. Despite this limitation, we could show positive proof of principle regarding the validity of follow-up assessments. Furthermore, even though the presence of tenosynovitis was examined via GSUS in all patients, we have decided to focus on synovial inflammation and compare joint OST scores with their respective US joint scores. The reason for that was the fact that OST is not validated in the assessment of tenosynovitis and that no tendon-specific scores are provided by the HandScan device. Interestingly, no association between tenosynovitis and OST was found in this cohort. Nevertheless, further examinations of the role of tendon inflammation are needed also in order to rule out an interference of tendon inflammation with OST assessment.Another possible limitation arises from the fact that a 4–13-MHz US probe was used and this could have led to reduced sensitivity, in particular in the area of small joints. However, our probe was operating at a frequency of 13 MHz and is thus comparable with the one used by the EULAR-OMERACT task force [