ABSTRACT
Introduction: There are inherent difficulties in making an accurate diagnosis or RA in early stages. The Aim of This Study was to determine the value or the anti -RA33 antibodies alone or in combination with MRI for the diagnosis or early RA and for the differential diagnosis of unclassified arthritis. Also, a comparison of ultrasonography, magnetic resonance imaging and plain radiography in their sensitivities for detection of early joint pathology in early RA was revised
Patients: This study included 67 patients. The patients were further classified into 3 main groups. Group I [18 patients]: patients with unclassified arthritis of less than 6 months duration. This group was followed up for 24 months. Group II [12 patients]: patients with established rheumatoid arthritis. Group III [37 patients]: patients with non - RA peripheral poly- or oligo-arthritis
Methods: For all the patients full clinical examination as well as routine laboratory investigations were performed in addition to anti-RA33 antibodies. Plain radiographs of affected joints were taken and repeated at least once during follow-up as well as anti- RA33 antibodies for the patients of unclassified group who developed RA. For the unclassified group, in addition, joint US and MRI were done
Results: Group I [n = 18]: In patients with unclassified arthritis, eight [44.44%] patients were negative for anti - RA33 and 10 patients were positive. Sixteen patients were negative for RF and 2 patients were positive for RF. After follow up period, 8 patients were negative for anti - RA33 and 10 patients were positive. However, 12 patients were negative for RF and 6 patients were positive. After follow up, 10 patients developed RA. From the 10 patients who developed RA, 8 patients were anti - RA33 positive and 2 patients were positive for RF at start of the study. At the end of the study, the percentage of the positive patients, for the anti - RA33 remained the same [80%]. However, the percentage of patients having positive RF increased up to 60%. The sensitivity of anti -RA33 in detecting early RA in this group was 80%, while that of RF was 20%. As regard radiological findings in our study, US was highly sensitive in diagnosis and quantification of synovitis in all patients with RA in early stage. However, it was less sensitive than MRI in detection of erosions and tenosynovitis. MRI sensitivity and specificity in detection of early RA was 70% and 75%. Combination of MRI with anti - RA33 in detection of early RA increased the sensitivity of both of them into 100%. In the unclassified group, the patients who developed later on RA had significantly less disease duration, significantly higher clinical probability of the disease with higher RAI, higher total leucocytic count, higher ESR as well as significantly higher anti - RA33 antibody level at the start of the study. Also, these patients had higher prevalence of erosions in MRI. In Group II [n = 12]: Patients with established rheumatoid arthritis: 4 patients were negative for anti - RA33 antibodies and 8 patients were positive. Also, 4 patients were negative for RF and 8 patients were positive. At the end of this study, we had 22 patients with RA, 12 were positive for the anti - RA33 antibodies and 10 were negative. Fourteen of them were positive for RF and 8 patients were negative for RA. Group UI [n = 37] patients with non - RA peripheral poly- or oligo-arthritis, when excluding the patients with SLE, the anti n RA33 was found to be negative in all patients with other forms of arthritis. ln the meantime, RF was found to be positive in 6 patients. ln SLE patients [n = 9] the anti - RA33 was found to be positive in 6 patients and RF was positive in 4 cases. The anti - RA33 showed highly significant correlation with the presence of active nephritis and significant correlation with erosive arthropathy. At the end of this study, the sensitivity and the specificity diagnosis of RA by using anti - RA33 antibody was 72.73%, and 83.78% respectively and that of MRI in detection of early RA was 70% [7/10] and 75% [6/8]. The sensitivity raised up to 100%, when using both tools in the diagnosis
Conclusion: Anti-RA33 autoantibody is a marker for early RA. It can differentiate RA from other non-RA rheumatological arthritis. Also, it can define a subset of SLE patients with erosive arthritis and active nephritis. MRI is a sensitive method in detecting erosion in early RA. Anti-RA33 antibody assay together with MRI can be very useful as adjunctive criteria to the ACR classification criteria for diagnosis of early RA