Background The performance of the 2010 ACR/EULAR classification criteria for rheumatoid arthritis (RA) using ultrasonography (US) as an alternative instrument to detect synovitis has recently been tested (1).

Objectives To evaluate the impact of the addition of US on the performance of the 2010 criteria in early arthritis patients, considering the use of disease modifying antirheumatic drugs (DMARDs) 12 months after the first evaluation as reference standard for diagnosis.

Methods Patients attending for the first time an early arthritis clinic before the 2010 criteria were published, presenting with at least one swollen joint and no alternative diagnosis, were included. US of bilateral wrists and metacarpophlangeal joints (1-5) was performed at baseline; Grey-scale (GS) and power-Doppler (PD) synovitis were semi-quantitatively scored(0-3). Overall GS and PD scores were obtained as the sum of the score of each joint. RA patients (1987 criteria) were given methotrexate (MTX) or, if contraindicated, other DMARDs (sulphasalazine, leflunomide, cyclosporine), undifferentiated polyarthritis patients received hydroxichloroquine(HCQ). Patients were seen every two months in the first semester and then every three. HCQ was substituted by MTX, MTX escalated up to the maximum tolerated dose and biologics added if Disease Activity Score was ≥2.4 at subsequent visits. The 2010 classification criteria were applied at baseline, the use of synthetic or biologic DMARDs (except HCQ) after 12 months was considered as reference standard. Logistic regression was applied to evaluate the predictive value of GS and PD scores. The additional value of GS score and PD scores on the performance of the criteria was tested using the likelihood ratio test. The performance of the criteria and of the addition of US was evaluated examining the area under the curve (AUC). Only patients with complete clinical and US data were included.

Results 188 patients with complete data, from a larger cohort, were included, 74% were female, mean age (sd) was 57.6 (±15.0), median (IQR) disease duration 3.07 (1.2,7.1) months, 32% were rheumatoid factor positive, 69.1% had RA according to the 1987 criteria, 80.8% according to the 2010 criteria. After 12 months 157/188 (83.5%) patients were taking DMARDs. Using 12 month DMARDs as reference standard, the AUC for the 2010 classification criteria was 0.82. GS score predicted DMARD use with an odds ratio (OR) (95% CI) of 1.14 (1.04,1.25). The addition of GS scores ≥5 but <10 led to an OR of 1.25 (0.51,3.02), while scores ≥10 had an OR of 5.13 (1.62,16.18). The addition of the GS score to the criteria increased the AUC to 0.85 (p=0.05). PD score predicted DMARD use as well (OR 1.15 (1.02,1.29)). PD scores ≥2 led to an OR of 2.74 (1.0,7.52), and the addition of PD score (cut-off of 2) to the criteria significantly improved their performance (AUC 0.85, p<0.05).

Conclusions The addition of single US features (GS and PD scores) significantly improves the performance of the 2010 RA classification criteria. The integration of different US features might give further information for classification.

References

1. Nakagomi D, Arthritis Rheum 2013: doi: 10.1002/art.37848

Disclosure of Interest None Declared