Value of high resolution MRI in the differential diagnosis ofpsoriatic arthritis, rheumatoid arthritis, erosive osteoarthritis and crystallinearthropathies

MRI is an effective imaging modality for the differential diagnosis and follow-up of inflammatory arthritis of the hand. In this study, we established a fine-tuned hand MRI protocol and aimed to demonstrate inflammatory findings at hand through the detailed assessment provided by the MRI. We investigated how effective MRI is in the differential diagnosis of inflammatory arthritis, particularly in the early stages. We conducted the study in a collaborative effort between the Departments of Radiology and Rheumatology at Hacettepe University with 57 patients, who presented to the rheumatology outpatient clinic between September 1, 2021, and June 1, 2024, and met the inclusion criteria. We gathered demographic, radiographic, and MRI findings and created a comprehensive data set. The mean age was 54±12 years and 73.6% of the patients were female. The distribution of the final diagnosis groups within the study group was as follows: 11 psoriatic arthritis (PsA), 14 rheumatoid arthritis (RA) (six seropositive (SpRA), eight seronegative (SnRA)), 11 erosive osteoarthritis and/or calcium pyrophosphate dihydrate crystal deposition disease (EOA±CPPD), 21 arthritis with distal interphalangeal joint involvement (ADIPI). In the first step, we analyzed the relationships between the final diagnosis groups and MRI findings and made pairwise comparisons between the groups. In the second step, we created a logistic regression model to identify risk factors for PsA. In the last step, we analyzed the correlation between the preliminary MRI and the patient's final diagnosis. When comparing the groups regarding MRI findings, we observed no difference between PsA and ADIPI except for nail bed enthesitis. Nail bed enthesitis was more common in the ADIPI group than PsA (p=0.048). There was no significant difference between SpRA and SnRA groups. Although not statistically significant, subcortical osteitis was more common in the SpRA group (83.3%) than SnRA group (%25) (p=0.103). In comparison between PsA and RA (SnRA+SpRA), there was a difference in enthesitis (p=0.033) and periarticular soft tissue edema (p=0.042); these findings were more frequent in PsA. In our further analysis after combining the ADIPI and PsA groups due to their similar MRI features, enthesitis (ligamentous enthesitis, extensor peritendinitis, nail bed enthesitis) and periarticular soft tissue edema were much more common in this combined group compared to the other groups (p<0.001). Although not statistically significant, it was noteworthy that 7 of the 9 diaphyseal osteitis seen in the entire study group were in the PsA+ADIPI group. In our analysis to determine the risk factors of PsA, we found that those with enthesitis were 24.27 times more likely to be in the PsA+ADIPI group than those without enthesitis (95% CI: 2.624 - 63.309). The accurate classification rate of the model was 83.7%, and the area under curve (AUC) value was 0.81. The coefficient of correlation between the radiologist's preliminary diagnosis and the rheumatologist's final diagnosis was 0.90 (95% CI: 0.812 - 0.961).