Diagnostic and prognostic potential of joint imaging in patients with anti-citrullinated protein antibodies

Sammanfattning: The introduction of novel therapeutic strategies set new goals for the patients’ outcome, which aims to achieve remission. This goal requires early diagnosis of RA and prompt efficient pharmacotherapy. The introduction of anti-citrullinated protein antibodies (ACPA) two decades ago allowed an earlier RA diagnosis. However, there are indications that ACPA positivity is still associated with higher rates of radiographic damage. As the small joints in hands and feet commonly are the first involved sites of inflammation, the role of different imaging modalities were studied regarding their diagnostic and prognostic impact for assessment of arthritis in RA. Further, ultrasound (US) and radiography were used to study the association between RA-specific antibodies and the occurrence of arthritis and joint damage in systemic lupus erythematosus (SLE).The use of US allows assessment of soft tissue like joint capsules, tendons and bursae. Used for a live scanning, it is easy to detect effusions and edema. Doppler indicates vasoproliferation were inflammation is present. Also, US seems to be more sensitive than radiography to detect minimal structural changes located at bone surfaces. We wanted to investigate whether US findings in a pre-RA stage can predict development of arthritis.Digital X-ray radiogrammetry (DXR) is a technique based on computerized analyses of standard hand radiographs to calculate peripheral bone mineral density (BMD) of the three middle metacarpal bones (DXR-BMD). In order for early treatment decisions, we aimed to study whether changes in DXR-BMD loss after 3 months can predict radiographic damage in early RA.In conclusion, the studies showed that ACPA-positivity is still associated with a higher risk of radiographic damage regardless of early treatment decisions. Therefore, close radiographic monitoring and readiness to intensive treatment is warranted in ACPA-positive patients. This thesis also shows that erosions detected by US in ACPA-positive patients with arthralgia predict development of clinical arthritis. Also, the magnitude of DXR-BMD loss helps identify patients at higher risk for future radiographic damage, and may therefore help to improve early treatment decisions. Finally, US and radiography confirm a higher rate of arthritis and erosions also in SLE patients who are positive for RA-specific antibodies.