Immunohistological analysis of synovial tissue for differential diagnosis in early arthritis

Objective. An early diagnosis in patients presenting with arthritis is impo rtant to provide information about prognosis and to initiate treatment. The objective of this study was to determine which markers applied in immunohi stological analysis of synovial tissue (ST) specimens could be used to diff erentiate rheumatoid arthritis (RA) from other forms of arthritis. Methods. Synovial biopsies were obtained by blind needle techniques from 95 patients with early arthritis. After follow-up of at least 2 yr to verify the diagnosis, the patients could be classified as follows: RA (n = 36), un differentiated arthritis (UA: n = 21), osteoarthritis (OA; n = 17), reactiv e arthritis (ReA: n = 10), ankylosing spondylitis (AS; n = 3), psoriatic ar thritis (PsA; n = 2) and crystal-induced arthritis (CA; n = 6). ST sections were analysed by immunohistochemistry using monoclonal antibodies against CD3, CD4, CD8, CD22 (B cells), CD38 (plasma cells), CD68 (macrophages) and CD55 (fibroblast-like synoviocytes). Results. Logistic regression analysis revealed that the higher scores for t he numbers of CD38+ plasma cells and CD22+ B cells in RA were the best disc riminating markers comparing RA to non-RA patients (CD38: P = 0.0001; CD22: P < 0.05). Polychotomous regression analysis comparing three diagnostic ca tegories(1: RA; 2: UA, ReA, AS and PsA; 3: OA and CA) also identified the s core for the number of CD38+ plasma cells (P < 0.0001) as well as the numbe rs of CD68+ macrophages in the synovial sublining (P = 0.05) as discriminat ing markers. Conclusion. The results suggest that immunohistochemical analysis of ST spe cimens from early arthritis patients can be used to differentiate RA from n on-RA patients. The numbers of plasma cells, B cells and macrophages are es pecially increased in ST of patients with RA. Future studies in early arthr itis patients with clinical Features which do not allow an immediate confid ent diagnosis may clarify the role of this test system in differential diag nosis.