SAT0713 Incidence of erosive interphalangeal oa is strongly associated with age, female gender, white race, and pre-existing hand oa: data from the osteoarthritis initiative

Background Symptomatic erosive interphalangeal OA (SEIPOA) is differentiated from hand OA by the presence of central joint erosions and is more strongly associated with hand pain, disability and finger deformity. There are no specific treatments for SEIPOA and relatively little is known about its incidence and natural history. Methods We evaluated participants in the Osteoarthritis Initiative (OAI), a multicenter cohort study of 4796 adults with or at risk for symptomatic knee OA recruited at 4 clinical sites between February 2004 and May 2006, which included postero-anterior radiographs of one or both hands at baseline and at 48 months, as well as questions about joint pain including the hand (based on a homunculus where patients indicated left or right hand pain) and self-reported physician-diagnosed hand OA. Trained readers scored the severity of OA in 16 joints of the dominant hand using the Kellgren Lawrence scale and classified presence of central erosions according to the OARSI Atlas of radiographic features: 2nd-5th distal interphalangeal (DIP) joints, 2nd-5th proximal interphalangeal (PIP) joints, 1st-5th metacarpophalangeal (MCP) joints, thumb interphalangeal (IP) joint, thumb-base joints (i.e., first carpometacarpal (CMC-1) joint and the scaphotrapezial (ST) joint). We classified erosive interphalangeal OA (EIPOA) based on presence of OA (KL ≥2) in at least one IP joint on two different fingers (excluding thumb base joints) with at least one with a central erosion and symptomatic erosive interphalangeal OA (SEIPOA) if there was also a report of hand pain. Baseline characteristics were examined by incident SEIPOA and EIPOA using ANOVA for continuous variables and chi-square analysis for categorical variables. Odds ratios were calculated to estimate the strength of association with incident SEIPOA. A p-value≤0.05 was considered significant. All analyses were conducted with SAS 9.4. Results 3604 participants had hand radiographs at baseline and 48 months; 18 radiographs were not readable and 121 had prevalent SEIPOA at baseline, leaving 3465 individuals eligible for analysis. The average age was 60.8 years (sd=9.1), 56.1% were female, and 81.3% were white. 133 individuals (3.8%) developed incident SEIPOA over the 4 year observation period. They had greater burden of IP OA at baseline (1.9 vs. 6.2 joints, p<0.001) and were more likely to report a diagnosis of hand OA (13.0% vs. 42.9%, p<0.001) than those who did not develop SEIPOA. 97.7% of the incident SEIPOA occurred in hands with radiographic hand OA, vs. 2.3% in hands without radiographic OA. SEIPOA incidence was strongly associated with older age, female gender, white race, smoking, lower BMI and lower level of physical activity (Image 1). Results were similar for radiographic EIPOA with the exception of the association with hypertension.Figure 1 Comparison of baseline characteristics by incident SEIPOA group Conclusions Incidence of SEIPOA in older people is substantial and approximates that of rheumatoid arthritis. SEIPOA is strongly related to age, female gender, and white race, develops in the setting of pre-existing hand OA, and is somewhat associated with reduced BMI and lower level of physical activity. Disclosure of Interest None declared