Biomarkers For Rheumatoid Arthritis Research Articles

Development of a multiplex assay based on chimeric citrullinated peptides as proof of concept for diagnosis of rheumatoid arthritis.

Anti-citrullinated peptide/protein antibodies (ACPAs) are the most specific serological biomarkers for rheumatoid arthritis (RA). They have both diagnostic and prognostic value, and are related to more aggressive joint disease in RA. However, a single biomarker cannot differentiate RA subtypes. So, simultaneous analysis of target citrullinated peptides, using a multiplex array based on chimeric peptides composed of several domains of human proteins, could be useful. In this work, eight chimeric peptides and the corresponding native arginine-containing control peptides were obtained by solid-phase peptide synthesis. The study included RA and psoriatic arthritis (PsA) patients attending the Rheumatology Unit of the Hospital Clinic in Barcelona, as well as healthy blood donors (BD) at the same hospital. Our main aim was to explore the diagnostic value of the novel multiplex array compared to a commercial ELISA-based ACPA assay in a serum-saving way. Using the combination of the eight chimeric peptide antigens in the multiplex array, 61.4% of the RA cohort were positive for 3 or more peptides; while, the healthy BD and PsA cohorts did not show any reactivity with the tested peptides. These results indicate that we have developed a highly specific multiplex assay based of chimeric citrullinated peptides derived from filaggrin, fibrin, vimentin and human enolase proteins for the detection of ACPAs in a serum-saving way.

Novel PET Radioligands as Inflammatory Biomarkers in Rheumatoid Arthritis and Myositis

Novel PET Radioligands as Inflammatory Biomarkers in Rheumatoid Arthritis and Myositis

E023 The use of CXCl13 as a biomarker in rheumatoid arthritis: a systematic review

E023 The use of CXCl13 as a biomarker in rheumatoid arthritis: a systematic review

LncRNA: An All-rounder in Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease and is supposed to have both genetic and environmental backgrounds. Plenty of studies have demonstrated the roles of long non-coding RNAs (lncRNAs) in the initiation and development of RA. Numerous lncRNAs have been found to be dysregulated in RA and to be correlated with disease activity of RA, which indicates potential diagnostic roles of lncRNAs. In addition to working as biomarkers for RA, lncRNAs participate in many specific pathological processes including inflammation, aberrant proliferation, migration, invasion and apoptosis. Further screenings and researches are required to validate the clinical potentials of lncRNAs as diagnostic and therapeutic targets in RA.

Elevated expression of interleukin-37 in patients with rheumatoid arthritis.

This study aims to discuss plasma and messenger RNA (mRNA) levels of interleukin (IL)-37 in rheumatoid arthritis (RA) patients and evaluate the potential of plasma IL-37 as a biomarker for RA. Plasma IL-37 levels and IL-37 mRNA relative concentrations were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). We discussed the association of IL-37 levels and clinical, laboratory parameters in RA patients in a training cohort. Plasma IL-37 levels were tested for discriminatory capacity by receiver operating characteristic (ROC) curve analysis. We then validated plasma IL-37 expression in a cohort of 598 patients (230 RA, 107 systemic lupus erythematosus [SLE], 100 osteoarthritis [OA], 62 gout, 51 primary Sjögren's syndrome [pSS], 48 ankylosing spondylitis [AS]). Both plasma levels of IL-37 and mRNA levels of IL-37 were elevated in RA patients compared to those in healthy controls in the training cohort, and there was a good diagnostic ability to predict RA (area under the curve [AUC]=0.97). Plasma IL-37 levels were significantly related to Disease Activity Score of 28 joints - erythrocyte sedimentation rate (DAS28-ESR) (rs =0.459, P<0.001). The levels of IL-37 mRNA were related to plasma IL-37 levels (rs =0.642, P<0.001), DAS28-ESR (r=0.641, P<0.001) and C-reactive protein (rs =0.603, P<0.001). In the validation cohort, when plasma IL-37 in RA patients compared with that in SLE, OA, gout, pSS and AS patients, the AUC was 0.86, 0.87, 0.91, 0.87, 0.92, respectively. IL-37 expression was increased in RA patients, and correlated with disease activity. IL-37 may be a biomarker for the diagnosis of RA.

A Study on Association Between Protein Carbonyl and Anti-cyclic Citrullinated Peptide Antibody in Rheumatoid Arthritis: Introducing a New Supplementary Biomarker.

Redox state and immune mechanisms are two major factors implicated in rheumatoid arthritis (RA). Regarding some limitations of anti-cyclic citrullinated peptide (anti-CCP) antibody in RA diagnosis, recruiting another strong marker of oxidative stress could lead to more definitive diagnosis. To evaluate the potential of protein carbonyl content as a supplementary biomarker for RA. Eighty patients with RA attending the Research Center from 2015 to 2016 were recruited in this study. Smoker and alcoholic subjects, or those with any other systemic illness were excluded from the study. Demographic information and clinical data were collected. Numbers of swollen and tender joints were determined and RA disease activity was assessed. Serum samples were used for assessing protein carbonyl level, platelet count, and anti-CCP antibody values. Statistical analyses for significant differences were performed according to parametric (Student t test) and nonparametric (Mann-Whitney test) tests. The correlation was determined by Pearson coefficient. There was a significant correlation between protein carbonyl levels and anti-CCP antibodies in active RA (p value = 0.01), but not in remission phase (p value = 0.28). A significant positive correlation was observed between protein carbonyl levels and platelets count in active RA (p value = 0.001), but not in remission phase (p value = 0.85). Protein carbonyl could be considered as a future cost-effective supplementary biomarker, alongside anti-CCP antibody, in active RA diagnosis as it showed a significant positive correlation with anti-CCP antibody and platelet, two major mediators in the disease pathogenesis.

Analysis of differentially expressed genes in rheumatoid arthritis and osteoarthritis by integrated microarray analysis.

Rheumatoid arthritis (RA) and osteoarthritis (OA) were two major types of joint diseases. This study aimed to explore the mechanism underlying OA and RA and analyze their difference by integrated analysis of multiple gene expression data sets. Gene expression data sets of RA and OA were downloaded from The Gene Expression Omnibus. Shared and specific differentially expressed genes (DEGs) in RA and OA were identified by integrated analysis of multiple gene expression data sets. Functional annotation and protein-protein interaction (PPI) network construction of OA- and RA-specific DEGs were performed to further explore the molecular mechanisms underlying RA and OA and analyze the mechanism differences between them. Compared with normal controls, 3757 and 2598 DEGs were identified in RA and OA, respectively. Among them, 2176 DEGs were RA-specific DEGs and 1017 DEGs were OA-specific DEGs. Moreover, the expression of 17 DEGs played opposite pattern in RA and OA compared with normal controls. Chemokine signaling pathway and oxidative phosphorylation were significantly enriched pathways for RA- and OA-specific DEGs, respectively. BIRC2 and CSNK1E were respective hub genes of RA- and OA-specific PPI network. Our findings provided clues for the specific mechanism and developing specific biomarkers for RA and OA.

Oral administration of alpha-lipoic acid did not affect lipid peroxidation and antioxidant biomarkers in rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is a chronic inflammatory disease in which oxidative stress could play a substantial pathological role. Alpha-lipoic acid (ALA) has been known as a "universal" and "ideal" antioxidant. The purpose of this study was to investigate the effects of oral administration of Alpha-lipoic acid (ALA) on lipid peroxidation and antioxidant biomarkers in Rheumatoid arthritis (RA) patients. The study was a randomized, double-blinded, placebo-controlled clinical trial. 70 RA patients were randomized 1:1 to two groups using blocked randomization method and received 1200mg/day ALA or placebo for 8 weeks. Fasting blood samples were obtained before and after the intervention to analyze total antioxidant capacity (TAC), antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and arylesterase (ARE) activities] and malondialdehyde (MDA). We observed significant increase in serum TAC (0.11 mmol/L; p=0.033) and ARE (13.76 U/mL; p=0.046) and significant decline in MDA (-0.36 nmol/L; p=0.002), in ALA group. However, these changes in ALA-treated group were not statistically significant when compared with placebo-treated group (p > 0.05). Also, within- and between-group differences of whole blood SOD and GSH-Px were not statistically significant (p > 0.05). In conclusion, unexpectedly, ALA therapy did not affect the oxidative status of RA patients in the present clinical trial. It seems that more comprehensive clinical trials in RA patients are still warranted to clarify the effectiveness of ALA which has been known as a potent antioxidant.

Pathogenic effects of anti-citrullinated protein antibodies in rheumatoid arthritis - role for glycosylation.

The identification in 1998 of the main antigenic substrate recognized by autoantibodies was a dramatic turning point in our understanding of rheumatoid arthritis (RA) biology. Now, two decades later, antibodies to citrullinated proteins are viewed no longer as mere biomarkers for RA, but also as major pathophysiological factors involved in the development of bone loss and joint pain. These pathogenic effects are ascribable to abnormal autoantibody glycosylation via a pathway involving the Th17T cells. In the future, abnormal autoantibody glycosylation may serve as a disease activity biomarker and suggest novel treatment strategies.

The oncoprotein TBX3 is controlling severity in experimental arthritis

BackgroundDevelopment of autoimmune diseases is the result of a complex interplay between hereditary and environmental factors, with multiple genes contributing to the pathogenesis in human disease and in experimental models for disease. The T-box protein 3 is a transcriptional repressor essential during early embryonic development, in the formation of bone and additional organ systems, and in tumorigenesis.MethodsWith the aim to find novel genes important for autoimmune inflammation, we have performed genetic studies of collagen-induced arthritis (CIA), a mouse experimental model for rheumatoid arthritis.ResultsWe showed that a small genetic fragment on mouse chromosome 5, including Tbx3 and three additional protein-coding genes, is linked to severe arthritis and high titers of anti-collagen antibodies. Gene expression studies have revealed differential expression of Tbx3 in B cells, where low expression was accompanied by a higher B cell response upon B cell receptor stimulation in vitro. Furthermore, we showed that serum TBX3 levels rise concomitantly with increasing severity of CIA.ConclusionsFrom these results, we suggest that TBX3 is a novel factor important for the regulation of gene transcription in the immune system and that genetic polymorphisms, resulting in lower expression of Tbx3, are contributing to a more severe form of CIA and high titers of autoantibodies. We also propose TBX3 as a putative diagnostic biomarker for rheumatoid arthritis.

The importance of red cell distribution width and neutrophil-lymphocyte ratio as a new biomarker in rheumatoid arthritis

Objectives: Rheumatoid arthritis (RA) is a long-lasting autoimmune disorder that primarily affects the joints. Various biomarkers have been used for the prognosis and clinical follow-up. There are few studies that have investigated whether or not neutrophil-lymphocyte ratio (NLR) and red cell distribution width (RDW) are good indicators of systemic inflammation. The present study aims to explore the prognostic value of RDW and NLR in rheumatoid arthritis (RA) as a new inflammatory marker. Methods: RA patients (n = 124) who presented to the Rheumatology outpatient clinic in our hospital between March 2015 and May 2015 were included in this study retrospectively. As a first group, 47 clinically active RA patients who had high acute phase proteins were included. In the second group, 73 clinically in-remission RA patients who had normal acute phase proteins were included. Fifty-five healthy volunteers constituted the control group. Results: The mean RDW was found to be 15.2 ± 2.9 in the active group; 14.6 ± 2 in the inactive group and 13.4 ± 1.4 in the control group (p &amp;lt; 0.01). The mean NLR was found to be 3.7 ± 2.2 in the active group; 3.7 ± 1.6 in the inactive group and 3.2 ± 0.9 in the control group (p = 0.190). There were statistically significant differences between the RDW values of the active-period RA patients with the control group (p &amp;lt; 0.01). There was statistically significant difference between RDW values of active RA and inactive RA patients (p &amp;lt; 0.01). The NLR results between the RA group and the control group (p = 0.700); the active RA group, and the inactive RA group (p = 0.169) were similar. There was not statistically difference between the NLR values of active RA patients with the control group (p = 0.360). There was statistically difference between the NLR values of inactive RA patients with the control group (p = 0.047). Conclusion: RDW was found higher in all RA group than control, additionally was also higher in active RA group than remission group. NLR values of remission group was higher than control.

Proteomic Analysis of Cerebrospinal Fluid: A Search for Biomarkers of Neuropsychiatric Systemic Lupus Erythematosus

Background: Neuropsychiatric systemic lupus erythematosus or NPSLE, as its name suggests, refers to the neurological and psychiatric manifestations of Systemic Lupus Erythematosus (SLE). In clinical practice, it is often difficult to reach an accurate diagnosis, as this disease presents differently in different patients, and the available diagnostic tests are often not specific enough. Objectives: The aim of this study was to search for proteomic biomarkers in cerebrospinal fluid that could be proposed as diagnostic aids for this disease. Methods: The proteomic profile of cerebrospinal fluid samples of 19 patients with NPSLE, 12 patients with SLE and no neuropsychiatric manifestation (SLEnoNP), 6 patients with neuropsychiatric symptoms but no SLE (NPnoSLE), 5 with Other Autoimmune Disorders without neuropsychiatric manifestations (OADs), and 4 Healthy Controls (HC), were obtained by two-dimensional gel electrophoresis and compared using ImageMaster Platinum 7.0 software. Results: The comparative analysis of the different study groups revealed three proteins of interest that were consistently over-expressed in NPSLE patients. These were identified by mass spectrometry as albumin (spot 16), haptoglobin (spot 160), and beta-2 microglobulin (spot 161). Conclusion: This work is one of the few proteomic studies of NPSLE that uses cerebrospinal fluid as the biological sample. Albumin has previously been proposed as a potential biomarker of rheumatoid arthritis and SLE, which is coherent with these results; but this is the first report of haptoglobin and beta-2 microglobulin in NPSLE, although haptoglobin has been associated with increased antibody production and beta-2 microglobulin with lupus nephritis.

Comparative study for haplotype block partitioning methods - Evidence from chromosome 6 of the North American Rheumatoid Arthritis Consortium (NARAC) dataset.

Haplotype-based methods compete with “one-SNP-at-a-time” approaches on being preferred for association studies. Chromosome 6 contains most of the known genetic biomarkers for rheumatoid arthritis (RA) disease. Therefore, chromosome 6 serves as a benchmark for the haplotype methods testing. The aim of this study is to test the North American Rheumatoid Arthritis Consortium (NARAC) dataset to find out if haplotype block methods or single-locus approaches alone can sufficiently provide the significant single nucleotide polymorphisms (SNPs) associated with RA. In addition, could we be satisfied with only one method of the haplotype block methods for partitioning chromosome 6 of the NARAC dataset? In the NARAC dataset, chromosome 6 comprises 35,574 SNPs for 2,062 individuals (868 cases, 1,194 controls). Individual SNP approach and three haplotype block methods were applied to the NARAC dataset to identify the RA biomarkers. We employed three haplotype partitioning methods which are confidence interval test (CIT), four gamete test (FGT), and solid spine of linkage disequilibrium (SSLD). P-values after stringent Bonferroni correction for multiple testing were measured to assess the strength of association between the genetic variants and RA susceptibility. Moreover, the block size (in base pairs (bp) and number of SNPs included), number of blocks, percentage of uncovered SNPs by the block method, percentage of significant blocks from the total number of blocks, number of significant haplotypes and SNPs were used to compare among the three haplotype block methods. Individual SNP, CIT, FGT, and SSLD methods detected 432, 1,086, 1,099, and 1,322 associated SNPs, respectively. Each method identified significant SNPs that were not detected by any other method (Individual SNP: 12, FGT: 37, CIT: 55, and SSLD: 189 SNPs). 916 SNPs were discovered by all the three haplotype block methods. 367 SNPs were discovered by the haplotype block methods and the individual SNP approach. The P-values of these 367 SNPs were lower than those of the SNPs uniquely detected by only one method. The 367 SNPs detected by all the methods represent promising candidates for RA susceptibility. They should be further investigated for the European population. A hybrid technique including the four methods should be applied to detect the significant SNPs associated with RA for chromosome 6 of the NARAC dataset. Moreover, SSLD method may be preferred for its favored benefits in case of selecting only one method.

A smart nanosensor for the detection of human immunodeficiency virus and associated cardiovascular and arthritis diseases using functionalized graphene-based transistors

Human immunodeficiency virus (HIV), which isa worldwide public health issue, is commonly associated with cardiovascular disorders (CVDs) and rheumatoid arthritis (RA). A smart nanosensor was developed for the detection of HIV and its related diseases (CVDs and RA) using graphene-based field-effect transistors (FETs). In this study, amine-functionalized graphene (afG) was conjugated with antibodies [anti-p24 for HIV, anti-cardiac troponin 1 (anti-cTn1) for CVDs, and anti-cyclic citrullinated peptide (anti-CCP) for RA] to detect various biomarkers. The antibodies were covalently conjugated to afG via carbodiimide activation. The bioconjugate (graphene-antibody) was characterized by various biophysical techniques such as UV–Vis, Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The electrochemical performance of the sensor was evaluated with respect to changes in the resistance of the electrode surface due to the interaction of the antigen with its specific antibody. The developed sensor was highly sensitive and showed a linear response to p24, cTn1, and, CCP from 1 fg/mL to 1 μg/mL. The limit of detection (LOD) was 100 fg/mL for p24 and 10 fg/mL for cTn1 and CCP under standard optimized conditions. The graphene-based smart nanodevice demonstrated excellent performance; thus, it could be used for the on-site detection of HIV, CVD, and RA biomarkers in real samples.

Development of a Novel Diagnostic Biomarker Set for Rheumatoid Arthritis Using a Proteomics Approach.

Background Rheumatoid arthritis (RA) is an autoimmune disease that starts with inflammation of the synovial membrane. Studies have been conducted to develop methods for efficient diagnosis of RA and to identify the mechanisms underlying RA development. Blood samples can be useful for detecting disturbance of homeostasis in patients with RA. Nanoliquid chromatography-tandem mass spectrometry (LC-MS/MS) is an efficient proteomics approach to analyze blood sample and quantify serum proteins. Methods Serum samples of 18 healthy controls and 18 patients with RA were analyzed by LC-MS/MS. Selected candidate biomarkers were validated by enzyme-linked immunosorbent assay (ELISA) using sera from 43 healthy controls and 44 patients with RA. Results Thirty-eight proteins were significantly differentially expressed by more than 2-fold in healthy controls and patients with RA. Based on a literature survey, we selected six candidate RA biomarkers. ELISA was used to evaluate whether these proteins effectively allow distinguishing patients with RA from healthy controls and monitoring drug efficacy. SAA4, gelsolin, and vitamin D-binding protein were validated as potential biomarkers of RA for screening and drug efficacy monitoring of RA. Conclusions We identified a panel of three biomarkers for RA which has potential for application in RA diagnosis and drug efficacy monitoring. Further, our findings will aid in understanding the pathogenesis of RA.

Serological Electrodetection of Rheumatoid Arthritis Using Mimetic Peptide

Rheumatoid arthritis is the most common inflammatory autoimmune disease in the world. Recently new targets for its detection were developed as alternatives to classic biomarkers, including the M-12 peptide, that mimics carbonic anhydrase III. Thus, the application of this peptide for the development of new detection devices is attractive. Our goal was to construct a modified electrode for immobilization of M-12 peptide and detection of a rheumatoid arthritis biomarker in serum of patients. 3-Hydroxybenzoic acid was electropolymerized onto graphite electrodes, and M-12 peptide was immobilized by adsorption. Negative and positive serum samples for rheumatoid arthritis were diluted and applied onto the electrode. Detection was carried in potassium ferrocyanide/ ferricyanide solution by differential pulse voltammetry. Atomic force microscopy and scanning electron microscopy were used to evaluate electrode surfaces. Cyclic voltammograms indicated the poly(3-hydroxybenzoic acid) formation and increase of electroactive area. Immobilization of M-12 probe increased current by 1.2 times, and negative serum addition caused no suitable difference. However, positive serum showed expressive decrease in the current signal of about 2.2 times, possibly due to steric hindrance when the anti-CA3 antibody interacts with the M-12 peptide, decreasing the electron transfer. Microscopies images corroborated with the electrochemical detection, showing evident changes in the morphology of the electrode surfaces. The bioelectrode was able to discriminate positive and negative serum samples of rheumatoid arthritis by a considerable decrease in the current signal value. Morphological analyses supported the electrochemical results. Thus, the constructed bioelectrode offers a new platform for detection of rheumatoid arthritis.

Decrease in 14-3-3η protein levels is correlated with improvement in disease activity in patients with rheumatoid arthritis treated with Tofacitinib

14-3-3η protein is a proinflammatory mediator that may represent a novel diagnostic and prognostic biomarker for rheumatoid arthritis (RA). We assessed the correlation between changes in serum 14-3-3η levels and changes in clinical disease activity measures in RA patients treated with Tofacitinib (TOF). Paired serum samples from 35 patients with RA were obtained at baseline and 5 months after the initiation of treatment with TOF. The levels of 14-3-3η were measured by JOINT stat 14-3-3η ELISA test kits (Augurex Life Sciences Corp.). The cut-off was defined as 0.19 ng/ml. 14-3-3η positivity was found in 57% of the patients at baseline and in 37% of the patients after 5 months of treatment. Mean ± SD baseline 14-3-3η levels [4.92 ± 8.86 ng/ml] were significantly higher (p < 0.005) than 14-3-3η levels following treatment [1.97 ± 4.59 ng/ml]. A statistically significant improvement (p < 0.001) of CDAI, SDAI, DAS4ESR and DAS4CRP was achieved after 5 month of treatment. Decrease in 14-3-3η protein levels was highly correlated with improvement in DAS4ESR (r = 0.50, p < 0.01), DAS4CRP (r = 0.46, p < 0.01) and ESR (r = 0.36, p = 0.03) and moderately correlated with improvement in CDAI (r = 0.32, p = 0.065) and SDAI (r = 0.33, p = 0.051). The correlation between decrease in 14-3-3η levels and improvement in DAS4ESR remained significant in a partial correlation analysis controlling for ESR (r = 0.39, p = 0.02). This study demonstrates that in RA patients who were treated with TOF, decrease in 14-3-3η levels is correlated with improvement in clinical disease activity parameters. The 14-3-3η protein may serve as an objective biomarker for monitoring of TOF therapy response.

Pathogenic Citrulline-Multispecific B Cell Receptor Clades in Rheumatoid Arthritis.

Anti-citrullinated protein antibodies (ACPAs) have proven highly useful as biomarkers for rheumatoid arthritis (RA). However, composition and functionality of the associated autoreactive B cell repertoire have not been directly assessed. We aimed to selectively investigate citrullinated autoantigen-specific B cell receptors (BCRs) involved in RA and initiate studies on their pathogenicity. Blood samples were obtained from patients in a University of Minnesota cohort with ACPA-positive RA (n = 89). Tetramer sets bearing citrullinated filaggrin peptide cfc1 or citrullinated α-enolase peptide were constructed to specifically capture autoreactive B cells from the unaltered, polyclonal repertoire in RA patients. Citrullinated peptide tetramer-bound B cells were subjected to flow cytometric cell sorting and single-cell IGH, IGK, and IGL gene sequencing for B cell lineage determinations. BCR gene sequences were also expressed as recombinant monoclonal antibodies (mAb) for direct evaluation of citrullinated autoantigen binding and effector functionality. Using citrullinated peptide tetramer enrichment to investigate single autoreactive blood B cells, we identified biased V-region gene usage and conserved junction arrangements in BCRs from RA patients. Parsimonious clustering of related immunoglobulin gene nucleotide sequences revealed clonal expansions of rare individual B cell clades, in parallel with divergent sequence mutations. Correspondingly, recombinant mAb generated from such BCR lineages demonstrated citrulline-dependent cross-reactivity extending beyond the citrullinated peptides used for B cell capture. A pair of citrullinated autoantigen-specific mAb with cross-reactive binding profiles also promoted arthritis in mice. Our findings suggest that broad ACPA specificities in RA arise from a restricted repertoire of evolving citrulline-multispecific B cell clades with pathogenic potential.

Proteomics Analysis for Verification of Rheumatoid Arthritis Biomarker Candidates Using Multiple Reaction Monitoring.

Rheumatoid arthritis (RA) is an autoimmune disease in which autoantibodies attack the synovial membrane, causing joint inflammation. Blood tests would offer a powerful, minimally invasive method for early diagnosis of RA. However, no reliable biomarkers for RA are presently available. The aim is to develop biomarkers for RA by multiple reaction monitoring (MRM)-based quantification of candidate biomarkers. Proteomics approaches are commonly used to identify and verify disease biomarkers. For discovery of biomarkers for RA, SWATH acquisition is performed and selected candidate biomarkers are validated by MRM. Target serum proteins are compared between patients with RA and healthy controls divided into three groups based on rheumatoid factor level. A total of 45 differentially expressed proteins are identified, as determined by SWATH acquisition. Of these, 13 proteins are selected as novel candidate biomarkers. A total of five proteins (transthyretin, gelsolin, angiotensinogen, lipopolysaccharide-binding protein, and protein S100-A9) are shown to have the potential to distinguish patients with RA from healthy controls. These five proteins may improve the efficiency of diagnosis of RA. MRM can be used to easily diagnose RA by detecting five proteins simultaneously in a single sample with high sensitivity.

Plasma interleukin-38 in patients with rheumatoid arthritis

Previous studies have indicated that interleukin-38 (IL-38) is involved in rheumatoid arthritis (RA). The present study aims to assess plasma levels of IL-38 in RA and discuss the potential of IL-38 as a biomarker for RA. Protein concentrations of IL-38 were examined by enzyme-linked immunosorbent assay, and the mRNA level of IL-38 was tested by quantitative real-time polymerase chain reaction. Plasma IL-38 was first compared in a training cohort, including 130 RA patients and 53 healthy controls, given the optimal cutoff. Then, we validated the levels of IL-38 in a further cohort of 519 patients, including 250 with RA, 63 systemic lupus erythematosus, 62 primary Sjogren's syndrome, 51 gout, 63 osteoarthritis, and 30 psoriatic arthritis, as well as 60 healthy controls. To further discuss the changes in IL-38 after treatment and the relationship with disease activity, we tested IL-38 expression in RA patients from the training cohort under follow-up. In the training cohort, plasma levels of IL-38 were higher in RA patients compared with healthy controls (681.00 [234.45–826.47] versus 152.04 [70.06–246.80] pg/mL, P < 0.001). The IL-38 mRNA level was elevated in RA patients as compared with healthy controls (P < 0.001). Expression of IL-38 was significantly higher in RA patients compared with that in non-RA patients in the validation cohort (all P < 0.001). Treatment significantly reduced IL-38 expression. IL-38 expression was related to parameters of inflammation both at baseline and in the follow-up studies. The area under the curve (AUC) of the receiver-operating characteristic curve showed that IL-38 may be a potential biomarker for RA. At the optimal cutoff value of 341.90 pg/mL, the sensitivity, specificity, and AUC were 72.30%, 90.60%, and 0.840, respectively, in the training cohort. Similar results were noted in the validation cohort. In conclusion, IL-38 expression correlated with RA disease activity, and plasma IL-38 might be a promising diagnostic biomarker for RA.