The Utility and Limitations of CRP, ESR and DAS28-CRP in Appraising Disease Activity in Rheumatoid Arthritis

Introduction Rheumatoid arthritis (RA) is a complex and clinically heterogeneous autoimmune disease. Currently, the relationship between pathogenic molecular drivers of disease in RA and therapeutic response is poorly understood. Methods We analyzed synovial tissue samples from two RA cohorts of 49 and 20 patients using a combination of global gene expression, histologic and cellular analyses, and analysis of gene expression data from two further publicly available RA cohorts. To identify candidate serum biomarkers that correspond to differential synovial biology and clinical response to targeted therapies, we performed pre-treatment biomarker analysis compared with therapeutic outcome at week 24 in serum samples from 198 patients from the ADACTA (ADalimumab ACTemrA) phase 4 trial of tocilizumab (anti-IL-6R) monotherapy versus adalimumab (anti-TNFα) monotherapy. Results We documented evidence for four major phenotypes of RA synovium – lymphoid, myeloid, low inflammatory, and fibroid - each with distinct underlying gene expression signatures. We observed that baseline synovial myeloid, but not lymphoid, gene signature expression was higher in patients with good compared with poor European league against rheumatism (EULAR) clinical response to anti-TNFα therapy at week 16 (P =0.011). We observed that high baseline serum soluble intercellular adhesion molecule 1 (sICAM1), associated with the myeloid phenotype, and high serum C-X-C motif chemokine 13 (CXCL13), associated with the lymphoid phenotype, had differential relationships with clinical response to anti-TNFα compared with anti-IL6R treatment. sICAM1-high/CXCL13-low patients showed the highest week 24 American College of Rheumatology (ACR) 50 response rate to anti-TNFα treatment as compared with sICAM1-low/CXCL13-high patients (42% versus 13%, respectively, P =0.05) while anti-IL-6R patients showed the opposite relationship with these biomarker subgroups (ACR50 20% versus 69%, P =0.004). Conclusions These data demonstrate that underlying molecular and cellular heterogeneity in RA impacts clinical outcome to therapies targeting different biological pathways, with patients with the myeloid phenotype exhibiting the most robust response to anti-TNFα. These data suggest a path to identify and validate serum biomarkers that predict response to targeted therapies in rheumatoid arthritis and possibly other autoimmune diseases. Trial registration ClinicalTrials.gov NCT01119859

Treatment with a chimeric mAb to TNF-alpha has been shown to suppress inflammation and improve patient well-being in rheumatoid arthritis (RA), but the mechanisms of action of such treatment have not been fully explored. Here we show that in vivo administration of anti-TNF-alpha Ab, using a longitudinal analysis, results in the rapid down-regulation of a spectrum of cytokines, cytokine inhibitors, and acute-phase proteins. Marked diurnal variation in the serum levels of some of these were detected. These results were consistent with the concept of a cytokine-dependent cytokine cascade, and the degree of clinical benefit noted after anti-TNF-alpha therapy is probably due to the reduction in many proinflammatory mediators apart from TNF-alpha, such as IL-6, which reached normal levels within 24 h. Serum levels of cytokine inhibitors such as soluble p75 and p55 TNFR were reduced as was IL-1 receptor antagonist. Reductions in acute-phase proteins occurred after serum IL-6 fell and included serum amyloid A, haptoglobin, and fibrinogen. The latter reduction could be of importance, as it is a risk factor for atherosclerosis, which is augmented in RA patients.

To assess whether radiologic progression occurs during clinical remission in patients with rheumatoid arthritis (RA). One hundred eighty-seven patients with RA in clinical remission were followed up clinically and radiologically for 2 years. Clinical remission was defined according to a modification of the American College of Rheumatology criteria (i.e., the criterion of fatigue was omitted, and patients had to fulfill 4 of the 5 remaining criteria). Radiologic joint damage was assessed by the Sharp/van der Heijde method. After 2 years of followup, remission persisted in 52% of patients. The median radiologic score for the total group of patients increased from 21 (interquartile range [IQR] 5, 65) at the time of entry to 25 (IQR 7, 72) after 2 years (P < 0.001). The median score for radiologic progression between baseline and 2 years was 0.5 (IQR 0, 2.5). Among patients with an exacerbation of RA (n = 86), the median score for progression over 2 years was 1.0 (IQR 0, 4.5) (P < 0.001), and in patients with a persistent remission (n = 93) it was 0 (IQR -0.5, 2.0) (P < 0.001). Clinically relevant progression of damage was more frequent in patients with exacerbation (23%) than in those with persistent remission (7%) (P = 0.001). However, in 15% of patients with persistent remission, an erosion developed in a previously unaffected joint. In the logistic regression analysis, the area under the curve of the Disease Activity Score, a continuous measure, was related to the chance of radiologic progression, regardless of the absolute disease activity level. Results were similar when other definitions of remission were used. Although rare, clinically relevant progression of joint damage does occur in patients with RA in prolonged remission. This suggests the need for markers that predict progression during periods of low disease activity and for drugs that prevent damage that is independent of disease activity.