A total of 126 patients were recruited for the study. Fourteen patients were excluded from analysis due to inadequate data regarding laboratory testing needed to calculate the 2010 RA criteria (no RF, ACPA, ESR and/or CRP; ) Patients who did not have complete laboratory data but still met the criteria based on a score of 6 or more were included. Therefore, 112 participants were included in the report. They had a mean age of 48.2 years (SD=15), with 77.7% (n=87) women, an average duration of disease of 5.3 years (SD=6.3) and 25% (n=28) were new patients diagnosed within the last 6 months. Patients were followed for an average of 6.3 months (SD=2.6). Twenty-eight patients (25.0%) were on non-steroidal anti-inflammatory drugs (NSAIDS) during the study, the majority of patients (n=96, 85.7%) were on additional medications, with 51 (45.5%) on corticosteroids, 82 (73.2%) on disease-modifying antirheumatic drugs (DMARD), 41 (36.6%) on biological and 6 (5.4%) on cytotoxic agents ().
Demographic and clinical features of 112 patients by 2010 ACR/EULAR RA criteria classification
Thirty (26.8%) patients had a primary diagnosis of RA made by their rheumatologist. The remainder had diagnoses of SLE (n=24, 21.4%), PsA (n=24, 21.4%), OA (n=12, 10.7%) and other rheumatic conditions (n=22, 19.6%)—spondyloarthritis (SpA) (n=8, 7.1%), undifferentiated autoimmune syndrome (UAS) (n=4, 3.6%), Sjogren's syndrome (SS) (n=3, 2.7%), gout (n=2, 1.8%), polymyalgia rheumatic (PMR) (n=1, 0.9%), undifferentiated inflammatory arthritis (n=1, 0.9%), mixed connective tissue disease (MCTD) (n=1, 0.9%), vasculitis (n=1, 0.9%) and Behcet's syndrome (n=1, 0.9%).
When the 2010 criteria were applied blindly to the patients, despite manifestations of other diseases that may have ruled out a diagnosis of RA, 66 (58.9%) did meet the ACR/EULAR 2010 RA criteria (score >=6) and 46 (41.1%) did not. In those with a known diagnosis of RA, 29 (96.7%) met the 2010 criteria. In the combined population of those without a rheumatologist diagnosis of RA (n=82), 37 (45.1%) fulfilled the new criteria. Among patients with other rheumatic diseases, 16 (66.7%) SLE patients, 8 (37.5%) PsA, 6 (50%) OA and 6 (27.2%) additional patients (two SS, two SpA, one gout and one MCTD) fulfilled the new criteria. Of the 28 subjects who newly presented to the office (within less than 6 months of study participation), 11 (39.3%) fulfilled the new criteria (2 with RA and 9 with other diseases—3 SLE, 3 PsA and 3 OA) and 17 did not.
The features of patients who fulfilled the 2010 criteria versus those who did not are shown in . Most of the patients who did not fulfil the criteria had a negative rheumatoid factor or ACPA and a joint count including larger joints or few small joints. However, of those that did fulfil the criteria, only about 49% were positive for high or low titre RF or ACPA while 82% had more than 10 small joints with synovitis or tenderness.
Comparison of sensitivity and specificity of 2010 vs 1987 rheumatoid arthritis criteria
We examined the same patients with application of the 1987 criteria in order to compare the two classification systems. Twenty-eight (93.3%) patients with RA fulfilled the 1987 criteria, as well as 18 (24.3%) without RA, 7 (38.9) with SLE, 7 (30.4) with PsA, none with OA and 4 (18.2%) with additional diagnoses.
The sensitivity and specificity of the 2010 criteria in classifying RA were 97% and 55%, respectively, compared with the 1987 RA criteria which were 93% and 76%, respectively. The 2010 criteria as applied to this group of patients had a poorer positive predictive (44% vs 61%) and a similar negative predictive value (98% vs 97%) versus the 1987 criteria ().
The ROC was calculated (). The sensitivity and specificity of the criteria in new patients, with less than 6 months of symptoms or two or less visits, were 100% and 65%, respectively. However, the number of new patients was limited, which restricts the use of this analysis.
Receiver–operator characteristic curves of ACR/EULAR RA criteria predicting MD diagnosis of ‘rheumatoid arthritis’.
We also applied criteria for SLE, PsA and OA to the subjects to test the accuracy of the diagnostic methods. Of those subjects who were diagnosed by their physician with SLE, 22 fulfilled the ACR SLE criteria along with four who did not have SLE and two with SLE did not fulfil the criteria, leading to a sensitivity and specificity of 92% and 95%, respectively. For those with PsA, 23 fulfilled the CASPAR criteria, one did not, and one person without PsA fulfilled the criteria, giving a sensitivity of 96% and specificity of 99%. For OA of the knee, 27 patients had a primary or secondary diagnosis of OA and 24 fulfilled the ACR knee OA criteria (either clinical, radiographic or laboratory), along with 29 who did not carry a diagnosis of OA. This had a sensitivity of 92% and specificity of 65%. These are all similar to previous publications for SLE, PsA and OA.10–12