Association of adiponectin, adenosine deaminase (ADA), and foot bone mineral density with disease activity and foot disability in rheumatoid arthritis

Rheumatoid arthritis (RA) often leads to foot disability, joint deterioration, and functional limitations. This study examined cross-sectional associations of adiponectin, adenosine deaminase (ADA), and foot bone mineral density (f-BMD), with high-sensitivity C-reactive protein (hs-CRP) as an additional inflammatory marker, in relation to disease activity and foot disability. This cross-sectional study involved 80 patients with RA and 80 age- and gender-matched healthy controls assessed between October 2014 and April 2015. The RA sample comprised 30 patients designated as early RA and 50 as established RA. Foot BMD, disease activity, foot function index (FFI), pain, radiographic analysis, and serum levels of adiponectin, ADA, and high sensitivity C- reactive protein (hs-CRP) were measured. Assessments were conducted using DEXA scans for BMD, validated questionnaires for FFI, and immunoassay techniques for inflammatory marker analysis. Foot pain/disability was reported by 59/80 patients (73.8%): 24/30 (80.0%) with early RA and 35/50 (70.0%) with established RA. Adiponectin, ADA, hs-CRP, DAS28-ESR, FFI, and radiographic values were numerically higher in established RA. The reported left/right foot BMD means were 0.69/0.71 g/cm 2 in early RA and 0.89/0.68 g/cm 2 in established RA. Biomarker coefficients with DAS28-ESR, FFI, and pain were positive, but varied in magnitude. Exploratory ROC estimates described comparisons of each RA subgroup with controls, not prediction of disease progression or a combined biomarker model. The reported descriptive patterns and correlation coefficients generate hypotheses about biomarker and foot-related measures in RA. They do not establish independent associations, causality, progression, monitoring performance, or diagnostic utility. Verification of the statistical outputs and confirmation in contemporary, prospectively followed cohorts are required before clinical interpretation of the biomarker thresholds. Trial registration ClinicalTrials.gov ID: NCT04036669 dated 30/07/2019.