Lack of a difference in increased capillary blood cell velocity in the skin over proximal interphalangeal joints between rheumatoid arthritis and osteoarthritis

Early detection of synovitis in rheumatoid arthritis (RA) and distinction from osteoarthritis (OA) are important to establish the most appropriate treatment. Increased perfusion over affected joints observed by laser Doppler perfusion imaging was supposed to arise from the underlying joint, because it was detected only by a near-infrared laser and not by a less penetrating red laser source. Using laser Doppler anemometry, this study addressed two questions: (1) whether capillary blood cell velocity (CBV) is increased in the skin over finger joints affected by RA or OA; (2) whether there is a difference between RA and OA in CBV above affected proximal interphalangeal (PIP) joints. Levels of soluble adhesion molecules were measured, because they indicate rheumatoid vasculitis raising flow resistance. Thirty-one patients with RA and 20 with OA were investigated. Compared to 18 controls, CBV (mean ± SEM) was elevated above PIP joints clinically affected by RA (0.35 ± 0.06 mm/s vs. 0.21 ± 0.02 mm/s; P < 0.05) and over PIP (0.27 ± 0.02 mm/s vs. 0.21 ± 0.02 mm/s; P < 0.05) and distal interphalangeal joints (0.27 ± 0.02 mm/s vs. 0.17 ± 0.01 mm/s; P < 0.001) affected by OA. Levels of soluble adhesion molecules were not correlated with CBV over PIP joints in RA. These observations demonstrated that elevated blood cell velocity is detectable by laser Doppler anemometry in skin capillaries over interphalangeal joints affected by RA or OA and contradict the previous assumption that there is hyperemia only in the affected joint. The lack of a significant difference in CBV over PIP joints between RA and OA patients might be due to some inflammation also occurring in OA rather than to vasculitic processes in RA associated with elevated levels of soluble adhesion molecules.