Serum amyloid a level and musculoskeletal ultrasound in assessment of disease activity in rheumatoid arthritis patients

Aim of the work

To assess serum amyloid A (SAA) level and study its relation to musculoskeletal ultrasound (MSUS) findings and to clinical disease activity indices in rheumatoid arthritis (RA) patients.

Patients and methods

60 RA patients and 60 matched controls were enrolled. Disease activity score-C-reactive protein (DAS-28-CRP) and simplified disease activity index (SDAI) and clinical disease activity Index (CDAI) were determined. MSUS evaluation was done using 12 -joint power Doppler ultrasound (PDUS) score. SAA was analyzed using an enzyme-linked immunosorbent assay.

Results

SAA levels were highly significant in patients (35.1 ± 3.6 mg/l) than in controls (1.6 ± 0.12 mg/l)(p < 0.001). There was significantly higher SAA level among steroid users (56.7 %)(p = 0.001) and a lower level among leflunomide users (30 %)(p = 0.04). SAA and PDUS significantly increased in patients with low disease activity (n = 13) compared to those in remission (n = 10)(p < 0.001). SAA significantly correlated with disease duration (p = 0.004), morning stiffness duration, swollen joint count, tender joint count, rheumatoid factor, anti-cyclic citrullinated peptide, DAS-28-CRP, SDAI, CDAI, erythrocyte sedimentation rate, CRP and total 12-joint PDUS score (p < 0.001). The highest discriminatory ability of active RA and remission was attributed to the combination of SAA, PDUS and CRP (accuracy = 96.7 %, AUC = 0.99; sensitivity 96 % and specificity 100 %).

Conclusion

RA patients have a significantly increased level of SAA which indicates a key pathogenic role in the disease. SAA level is a potentially effective biomarker in the assessment of disease activity in RAand allied to PDUS. Combining SAA, PDUS and CRP provide the highest sensitivity and specificity in discrimination of active RA from remission.