Detection of systemic autoimmune diseases in an ongoing assessment program for hand arthralgias. A comparative analysis with inflammatory and non-inflammatory arthropathies.

INTRODUCTION: Arthralgias are prevalent in systemic autoimmune rheumatic diseases (SARD), emphasizing the need for early recognition. This study aimed to estimate SARD frequency and compare clinical, laboratory, and imaging findings among SARD, non-inflammatory arthralgia (NIA), and RA in patients with hand arthralgias.

METHODS: A prospective evaluation program included individuals aged ≥18 with hand arthralgias. Baseline assessments covered clinical, laboratory, ultrasound, and radiography. Follow-up diagnoses categorized patients into SARD, NIA, and RA groups. Comparison between groups was performed using parametric and non-parametric tests. Two multivariate logistic regression analyzes were performed using the final diagnosis of SARD as the dependent variable (NIA and RA). ROC curves were calculated in those variables that presented an independent association in the multivariate analysis.

RESULTS: Among 1053 patients, 9.6% were SARD (SLE 47%). Comparing SARD with NIA revealed higher CRP levels, power Doppler, less rhizarthrosis in ultrasound, and more ANA positivity in SARD patients. Distinct differences were observed between SARD and RA patients in terms of pain levels, swollen joints, metacarpophalangeal involvement and morning symptoms. Diagnostic markers demonstrated specific sensitivities and specificities: ANA for SARD versus NIA (82%, 34%), US not finding rhizarthrosis for SARD versus NIA (66%, 85%), CRP (cut-off >2.5 mg/L) sensitivity 52%, specificity 60%, AUC 0.62, RA antibodies (RF, 11 IU/mL) sensitivity 76%, specificity 74%, AUC 0.8, ACPA (1.25) sensitivity 50%, specificity 98%, AUC 0.7, ANA+ sensitivity 95%, specificity 32%, AUC 0.7, and US absence of synovitis sensitivity 82%, specificity 34%, AUC 0.75.

CONCLUSION: This study highlights distinct clinical, laboratory, and imaging features differentiating SARD-related hand arthralgia from non-SARD hand arthralgia and RA.