The specificity of anti-carbamylated protein antibodies for rheumatoid arthritis in a setting of early arthritis.

INTRODUCTION: Anti-carbamylated protein (anti-CarP) antibodies have been described in rheumatoid arthritis (RA) and arthralgia patients at risk of developing RA. To what extent these autoantibodies are specific for RA is unknown. Therefore, we investigated the diagnostic performance of the presence of anti-CarP antibodies for RA in a setting of early arthritis. METHODS: Anti-CarP antibodies were detected using carbamylated fetal calf serum as substrate. Anti-CCP2 antibodies were measured using enzyme-linked immunosorbent assay and immunoglobulin M (IgM) rheumatoid factor (RF) as part of routine care. Sera were derived from patients in the Leiden Early Arthritis Clinic cohort obtained at inclusion. Test characteristics were determined using the fulfillment of the 2010 RA criteria after 1 year as outcome. RESULTS: In total 2086 early arthritis patients were studied regarding the presence of anti-CarP antibodies. We observed that the sensitivity and specificity of the presence of anti-CarP antibodies for RA were 44 % and 89 %, respectively. As a reference, sensitivity and specificity of the presence of anti-CCP2 antibodies were 54 % and 96 %, respectively, and of IgM-RF 59 % and 91 %. Patients harboring anti-CarP antibodies not classified as RA were mainly diagnosed with undifferentiated arthritis and less frequently reactive arthritis and psoriatic arthritis. CONCLUSION: Anti-CarP antibodies are predominantly present in RA but can also be detected in other forms of arthritis.

Reappraisal of the diagnostic and prognostic value of morning stiffness in arthralgia and early arthritis: results from the Groningen EARC, Leiden EARC, ESPOIR, Leiden EAC and REACH.

INTRODUCTION: Morning stiffness is assessed daily in the diagnostic process of arthralgia and arthritis, but large-scale studies on the discriminative ability are absent. This study explored the diagnostic value of morning stiffness in 5,202 arthralgia and arthritis patients and the prognostic value in early rheumatoid arthritis (RA). METHODS: In arthralgia patients referred to the Early Arthritis Recognition Clinics (EARC) of Leiden (n = 807) and Groningen (n = 481) or included in the Rotterdam Early Arthritis Cohort (REACH) study (n = 353), the associations (cross-sectional analyses) between morning stiffness and presence of arthritis at physical examination were studied. In early arthritis patients, included in the Leiden Early Arthritis Clinic (EAC) (n = 2,748) and Evaluation et Suivi de POlyarthrites Indifférenciées Récentes (ESPOIR) (n = 813), associations with fulfilling the 2010-RA criteria after one year were assessed. In 2010-RA patients included in the EAC (n = 1,140) and ESPOIR (n = 677), association with the long-term outcomes of disease-modifying antirheumatic drug (DMARD)-free sustained remission and radiological progression were determined. Morning stiffness was defined as a duration ≥60 minutes; sensitivity analyses were performed for other definitions. RESULTS: In arthralgia, morning stiffness (≥60 minutes) associated with the presence of arthritis; Leiden EARC odds ratio (OR) 1.49 (95% CI 1.001 to 2.20), Groningen EARC OR 2.21 (1.33 to 3.69) and REACH OR 1.55 (0.97 to 2.47) but the areas under the receiver operating characteristic curve (AUCs) were low (0.52, 0.57, 0.54). In early arthritis, morning stiffness was associated with 2010-RA independent of other predictors (Leiden EAC OR 1.72 (95% CI 1.31 to 2.25, AUC 0.68), ESPOIR OR 1.68 (1.03 to 2.74, AUC 0.64)). Duration of ≥30 minutes provided optimal discrimination for RA in early arthritis. Morning stiffness was not associated with radiological progression or DMARD-free sustained remission. CONCLUSIONS: Morning stiffness in arthralgia and early arthritis is associated with arthritis and RA respectively. This supports the incorporation of morning stiffness in the diagnostic process.

Evaluating processes underlying the predictive value of baseline erosions for future radiological damage in early rheumatoid arthritis.

OBJECTIVES: Baseline erosions are characteristic for rheumatoid arthritis (RA) and predictive for a severe disease course. The mechanisms leading to baseline erosions being a strong predictor for radiological progression are unknown. We aimed to increase this understanding by mediation analyses in an observational cohort and a cross-sectional MRI study. METHODS: 3256 hands and feet radiographs of 653 early RA patients assessed during 7 years of disease were scored using the Sharp-van der Heijde method. Mediation models and multivariate regression analyses were used to explore the association between baseline erosions, other predictors and radiological damage over time. 603 joints (MCP2-5 and MTP1-5) of 67 RA patients underwent 1.5 T MRI at baseline. Data on MRI inflammation were compared with clinical inflammation and baseline radiological erosions. RESULTS: Patients with baseline erosions had, at any point in time during 7 years, 3.45 times more joint damage than patients without erosions (p<0.001, 95% CI 3.00 to 3.98). Baseline erosions were an independent predictor and not a mediator between symptom duration, systemic or local clinical inflammation (erythrocyte sedimentation rate (ESR), swollen joint count (SJC)) or autoantibodies (anti-citrullinated-peptide antibodies, rheumatoid factor) and radiological damage. Subclinical MRI inflammation was studied in relation to erosions, revealing that 83% of the non-swollen joints with baseline erosions had subclinical MRI inflammation compared with 25% of the non-swollen joints without baseline erosions (OR 15.2 95% CI 3.1 to 102.1). The association between MRI inflammation and baseline erosions was independent of symptom duration, ESR, SJC and autoantibodies. CONCLUSIONS: Baseline erosions are a predictor for future joint damage, independent of known predictors as time, autoantibodies or clinical measurable inflammation. Subclinical inflammation is suggested as an underlying mechanism.

Characterising arthralgia in the preclinical phase of rheumatoid arthritis using MRI.

BACKGROUND: The phase of arthralgia is the earliest moment to clinically recognize patients who may develop Rheumatoid Arthritis (RA). Previous imaging studies in the arthralgia phase have shown that inflammation precedes RA development. It is unknown which symptoms/characteristics relate to subclinical joint inflammation as measured by MRI. Among all patients with arthralgia, those with clinically suspect arthralgia (CSA) are suspected to progress to arthritis according to the clinical judgement of their rheumatologists. We determined the symptoms/characteristics of patients with CSA who had inflammation on MRI. METHODS: 102 patients with CSA and without clinical arthritis were included. They completed questionnaires, underwent joint counts and unilateral 1.5 T MRI of MCP joints 2-4, wrist and MTP joints 1-5. Synovitis, bone marrow oedema (BME) and tenosynovitis were scored according to the OMERACT rheumatoid arthritis MRI scoring system. Symptoms and signs were related to MRI inflammation (based on MRI scores in symptom-free controls; a sum of synovitis, BME and tenosynovitis scores ≥3 was considered positive). Whether certain clinical characteristics frequently occurred together with MRI inflammation was studied by partial least squares analysis. RESULTS: MRI was performed in 93 patients with CSA, 44% of whom had subclinical MRI inflammation. Synovitis was the most prevalent inflammatory feature on MRI (20%). Patients with MRI inflammation were older and were more frequently positive for anti-citrullinated peptide antibodies than patients without MRI inflammation (p<0.001 and 0.049). In PLS analysis, including 16 clinical and serological characteristics as independent variables and MRI inflammation as dependent variable, no clear clusters of patients with and without MRI inflammation were identified. CONCLUSIONS: Subclinical inflammation as measured by MRI is present in 44% of patients with CSA. A combination of symptoms/characteristics incompletely differentiated patients with and without MRI inflammation.

Rheumatoid factor and anti-citrullinated protein antibody positivity, but not level, are associated with increased mortality in patients with rheumatoid arthritis: results from two large independent cohorts.

INTRODUCTION: This study aimed to investigate rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA) status and levels as predictors of mortality in two large cohorts of patients with early inflammatory arthritis (EIA). METHODS: Data from the Norfolk Arthritis Register (NOAR) and Leiden Early Arthritis Clinic (EAC) cohorts were used. At baseline, patients had demographic data and smoking status recorded; RF, ACPA and inflammatory markers were measured in the local laboratories. Patients were flagged with national death registers until death or censor date. Antibody status was stratified as negative, low or high positive by RF and ACPA levels individually. In addition, patients were grouped as seronegative, RF positive, ACPA positive or double antibody (RF and ACPA) positive. Cox regression models explored associations between antibody status and mortality adjusting for age, sex, smoking status, inflammatory markers and year of enrolment. RESULTS: A total of 4962 patients were included, 64% were female. Median age at onset was 56 (NOAR) and 54 (EAC) years. In NOAR and EAC respectively, 35% and 42% of patients were ACPA/RF positive. When antibody status was stratified as negative, low or high positive, there were no consistent findings between the two cohorts. Double antibody positivity was associated with excess mortality in both cohorts compared to seronegative patients: NOAR and EAC respective adjusted HR (95% confidence interval) 1.35 (1.09 to 1.68) and 1.58 (1.16 to 2.15). CONCLUSIONS: Patients with EIA who are seropositive for both RF and ACPA have increased mortality compared to those who are single positive or seronegative. Antibody level in seropositive patients was not consistently associated with excess mortality.

Subclinical inflammation on MRI of hand and foot of anticitrullinated peptide antibody-negative arthralgia patients at risk for rheumatoid arthritis.

INTRODUCTION: It is known that anticitrullinated peptide antibody (ACPA)-positive rheumatoid arthritis (RA) has a preclinical phase. Whether this phase is also present in ACPA-negative RA is unknown. To determine this, we studied ACPA-negative arthralgia patients who were considered prone to progress to RA for local subclinical inflammation observed on hand and foot magnetic resonance imaging (MRI) scans. METHODS: We studied a total of 64 ACPA-negative patients without clinically detectable arthritis and with arthralgia of the small joints within the previous 1 year. Because of the character of the patients' symptoms, the rheumatologists considered these patients to be prone to progress to RA. For comparisons, we evaluated 19 healthy, symptom-free controls and 20 ACPA-negative RA patients, who were identified according to the 1987 American Rheumatism Association criteria. All participants underwent MRI of unilateral wrist, metacarpophalangeal and metatarsophalangeal joints. Synovitis and bone marrow oedema (BME) were scored according to the OMERACT rheumatoid arthritis magnetic resonance imaging scoring system, and the scores were summed to yield the 'MRI inflammation score'. Scores were compared between groups. Among the ACPA-negative arthralgia patients, MRI inflammation scores were related to C-reactive protein (CRP) levels and the tenderness of scanned joints. RESULTS: MRI inflammation scores increased progressively among the groups of controls and ACPA-negative arthralgia and RA patients (median scores = 0, 1 and 10, respectively; P < 0.001). The MRI inflammation scores of ACPA-negative arthralgia patients were significantly higher than those of controls (P = 0.018). In particular, the synovitis scores were higher in ACPA-negative arthralgia patients (P = 0.046). Among the ACPA-negative arthralgia patients, inflammation was observed predominantly in the wrist (53%). The synovitis scores were associated with CRP levels (P = 0.007) and joint tenderness (P = 0.026). Despite the limited follow-up duration, five patients developed clinically detectable arthritis. These five patients had higher scores for MRI inflammation (P = 0.001), synovitis (P = 0.002) and BME (P = 0.003) compared to the other patients. CONCLUSION: Subclinical synovitis was observed in the small joints of ACPA-negative arthralgia patients, and especially in patients whose conditions progressed to clinically detectable arthritis. This finding suggests the presence of a preclinical phase in ACPA-negative RA. Further longitudinal studies of these lesions and patients are required to confirm this hypothesis.

Identification of a genetic variant for joint damage progression in autoantibody-positive rheumatoid arthritis.

BACKGROUND: Joint destruction is a hallmark of autoantibody-positive rheumatoid arthritis (RA), though the severity is highly variable between patients. The processes underlying these interindividual differences are incompletely understood. METHODS: We performed a genome-wide association study on the radiological progression rate in 384 autoantibody-positive patients with RA. In stage-II 1557 X-rays of 301 Dutch autoantibody-positive patients with RA were studied and in stage-III 861 X-rays of 742 North American autoantibody-positive patients with RA. Sperm-Associated Antigen 16 (SPAG16) expression in RA synovium and fibroblast-like synoviocytes (FLS) was examined using Real-Time Quantitative Polymerase Chain Reaction (RT-qPCR) and immunohistochemistry. FLS secrete metalloproteinases that degrade cartilage and bone. SPAG16 genotypes were related to matrix metalloproteinase (MMP)-3 and MMP-1 expression by FLS in vitro and MMP-3 production ex vivo. RESULTS: A cluster of single nucleotide polymorphisms (SNPs) at 2q34, located at SPAG16, associated with the radiological progression rate; rs7607479 reached genome-wide significance. A protective role of rs7607479 was replicated in European and North American patients with RA. Per minor allele, patients had a 0.78-fold (95% CI 0.67 to 0.91) progression rate over 7 years. mRNA and protein expression of SPAG16 in RA synovium and FLS was verified. FLS carrying the minor allele secreted less MMP-3 (p=1.60×10(-2)). Furthermore, patients with RA carrying the minor allele had lower serum levels of MMP-3 (p=4.28×10(-2)). In a multivariate analysis on rs7607479 and MMP-3, only MMP-3 associated with progression (p=2.77×10(-4)), suggesting that the association between SPAG16-rs7607479 and joint damage is mediated via an effect on MMP-3 secretion. CONCLUSIONS: Genetic and functional analyses indicate that SPAG16 influences MMP-3 regulation and protects against joint destruction in autoantibody-positive RA. These findings could enhance risk stratification in autoantibody-positive RA.

MRI of hand and foot joints of patients with anticitrullinated peptide antibody positive arthralgia without clinical arthritis.

BACKGROUND: Anticitrullinated peptide antibodies (ACPA) and acute phase reactants may be increased before arthritis becomes clinically detectable, suggesting that the processes underlying rheumatoid arthritis (RA) start preclinically. Whether local inflammation occurs in the preclinical phase is unknown. Therefore, we studied the small joints of ACPA positive arthralgia patients for local subclinical inflammation. METHODS: Imaging was performed using 1.5 T extremity MRI. Painful hand or foot joints of 21 ACPA positive arthralgia patients without clinical arthritis were imaged. For comparison, hand and foot joints of 22 ACPA positive RA patients and 19 symptom free controls were studied. Within ACPA positive arthralgia patients, painful and symptom free joint regions were imaged. Scoring was performed according to the Outcome Measures in Rheumatology Clinical Trials (OMERACT) Rheumatoid Arthritis Magnetic Resonance Imaging Scoring (RAMRIS) method. Analyses were performed on joint region level and focused on inflammation (synovitis plus bone marrow oedema). RESULTS: The mean combined inflammation scores of the metacarpophalangeal/proximal interphalangeal joints of controls, painful joints of ACPA positive arthralgia patients and ACPA positive RA patients were 0.1, 0.7 and 3.7, respectively (p<0.001). Likewise, the mean combined inflammation scores of the wrist were 0.9, 2.3 and 10.3, respectively (p<0.001) and that of the metatarsophalangeal joints 0.5, 0.9 and 3.8, respectively (p=0.10). At the MCP joints, the combined inflammation score was significantly correlated with C reactive protein and erythrocyte sedimentation rate levels (rs=0.83 and rs=0.78, respectively) CONCLUSIONS: The present data suggest that local subclinical inflammation occurs in ACPA positive arthralgia patients.

Improved early identification of arthritis: evaluating the efficacy of Early Arthritis Recognition Clinics.

OBJECTIVE: Only 31% of Dutch rheumatoid arthritis (RA)-patients visit a rheumatologist within 12 weeks after symptom onset; this is mainly due to delay at the level of the general practitioner (GP). In order to reduce delay of GPs in identifying early arthritis, we initiated an Early Arthritis Recognition Clinic (EARC). METHODS: EARCs were initiated at the Leiden and Groningen University Medical Centers. At this EARC, patients filled in a questionnaire about their symptoms, followed by a short visit with only a full joint examination by an experienced rheumatologist. If arthritis was present the patient got an appointment the same week at the regular outpatient clinic. The main outcome parameter was the GP-delay; the secondary outcome parameter was the total delay. In both centres, patients included in early arthritis clinics that had arrived via regular referrals served as control group. RESULTS: Four hundred patients visited the Leiden EARC and 212 patients the Groningen EARC. Arthritis was detected in 42% and 49% respectively. The median GP-delay for these arthritis patients was 2.0 (0.4-7.3) and 2.0 (0.4-10.0) weeks and the median total delay 8.6 (3.6-22.3) and 10.6 (3.1-30.8) weeks respectively. At these two clinics 59% and 51% of all arthritis patients and 65% and 53% of the patients that were subsequently diagnosed with undifferentiated arthritis or RA were seen within 12 weeks after symptom onset. In the Leiden and Groningen control groups that arrived via regular referrals, only 32% and 38% were seen within 12 weeks time. CONCLUSIONS: The EARC increased the early identification of arthritis and RA.

Reasons for medical help-seeking behaviour of patients with recent-onset arthralgia.

OBJECTIVE: Patient delay in seeking medical help may cause suboptimal use of the therapeutic window in rheumatoid arthritis. We aimed to assess the motivations and the urgency with which patients with arthralgia seek medical help. METHODS: 612 patients with arthralgia-visiting two Dutch Early Arthritis Recognition Clinics-were studied. Patients filled out a questionnaire with questions on their symptoms and their reasons for seeking medical help. Comparisons were made for patients with short or prolonged patient delay, patients with and without arthritis, age and gender. RESULTS: The median symptom duration was 4 weeks. A prolonged delay in seeking help was associated with a gradual onset of symptoms (78%) and the perception that symptoms would not be serious or would go away (16% and 48%, respectively). Arthralgia patients who promptly sought medical help more often had an acute onset of symptoms and more frequently reported impairments at work or in daily functioning than patients who postponed seeking help (all p<0.005). Patients with and without arthritis generally had similar reasons for seeking help. The proportion of patients who had a prolonged patient delay was comparable between male and female subjects and between age categories. Particularly younger patients postponed seeking help because they thought their symptoms would disappear spontaneously. CONCLUSIONS: This large-scale study observed several reasons and symptom characteristics influencing the help-seeking behaviour of persons with arthralgia. These data can be helpful to define strategies aiming at early identification of arthritis.

Interactive seminars or small group tutorials in preclinical medical education: results of a randomized controlled trial.

BACKGROUND: Learning in small group tutorials is appreciated by students and effective in the acquisition of clinical problem-solving skills but poses financial and resource challenges. Interactive seminars, which accommodate large groups, might be an alternative. This study examines the educational effectiveness of small group tutorials and interactive seminars and students' preferences for and satisfaction with these formats. METHODS: Students in year three of the Leiden undergraduate medical curriculum, who agreed to participate in a randomized controlled trial (RCT, n = 107), were randomly allocated to small group tutorials (n = 53) or interactive seminars (n = 54). Students who did not agree were free to choose either format (n = 105). Educational effectiveness was measured by comparing the participants' results on the end-of-block test. Data on students' reasons and satisfaction were collected by means of questionnaires. Data was analyzed using student unpaired t test or chi-square test where appropriate. RESULTS: There were no significant differences between the two educational formats in students' test grades. Retention of knowledge through active participation was the most frequently cited reason for preferring small group tutorials, while a dislike of compulsory course components was mentioned more frequently by students preferring interactive seminars. Small group tutorials led to greater satisfaction. CONCLUSIONS: We found that small group tutorials leads to greater satisfaction but not to better learning results. Interactive learning in large groups might be might be an effective alternative to small group tutorials in some cases and be offered as an option.

Improved treatment strategies reduce the increased mortality risk in early RA patients.

OBJECTIVE: A higher mortality rate in patients with RA than in the general population has been reported in most series. Treatment strategies for RA have improved dramatically over the last decades, resulting in less inflammation and joint damage. We investigated whether this change in treatment corresponds to reversal of excess mortality by studying a large inception cohort of early RA patients exposed to different treatment strategies. METHODS: Six hundred and eighty-four RA patients included in the Leiden Early Arthritis Clinic between 1993 and 2008 were studied. Treatment was different for three inclusion periods. From 1993 to 1995 patients were treated with NSAIDs and only late in their disease with DMARDs. From 1996 to 1998 patients were promptly treated with HCQ or SSZ. From 1999 to 2008 patients were immediately treated with MTX monotherapy or in combination with other disease-modifying drugs. Life/death status was tracked nationally using the civic registries. Mortality rates were compared with the general Dutch population. RESULTS: In Periods 1 and 2, increased standardized mortality rates were found, 1.35 (95% CI 0.94, 1.93) and 1.23 (95% CI 0.91, 1.67), respectively, while a decreased standardized mortality rate was found for patients included in 1999-2006 [0.49 (95% CI 0.31, 0.77)]. Age of onset [hazard ratio (HR) 1.10 (95% CI 1.07, 1.13)], erosive disease [HR 2.03 (95% CI 1.22, 3.37)], high CRP level [HR 1.09 (95% CI 1.01, 1.18)], smoking [HR 2.39 (95% CI 1.31, 4.38)] and higher baseline HAQ score [HR 1.53 (95% CI 1.06, 2.20)] associated with mortality. CONCLUSION: Current treatment strategies for early RA, such as that given in inclusion Period 3, might contribute to the reversal of excess mortality in RA.

TRAF1/C5 polymorphism is not associated with increased mortality in rheumatoid arthritis: two large longitudinal studies.

INTRODUCTION: Recently an association between a genetic variation in TRAF1/C5 and mortality from sepsis or cancer was found in rheumatoid arthritis (RA). The most prevalent cause of death, cardiovascular disease, may have been missed in that study, since patients were enrolled at an advanced disease stage. Therefore, we used an inception cohort of RA patients to investigate the association between TRAF1/C5 and cardiovascular mortality, and replicate the findings on all-cause mortality. As TRAF1/C5 associated mortality may not be restricted to RA, we also studied a large cohort of non-RA patients. METHODS: 615 RA patients from the Leiden Early Arthritis Clinic (EAC) (mean follow-up 7.6 years) were genotyped for rs10818488. In addition 5634 persons enrolled in the PROspective Study of Pravastatin in the Elderly at Risk (mean follow-up 3.2 years) were genotyped for rs2416808 (R(2) >0.99 with rs10818488). The life/death status was determined and for the deceased persons the cause of death was ascertained. Cox proportional hazards and regression models were used to assess hazard ratios (HR) and 95% confidence intervals (CI). RESULTS: Seventy-seven RA patients died. The main death causes in RA patients were cardiovascular diseases (37.7%), cancer (28.6%) and death due to infections (9.1%). No association was observed between the rs10818488 susceptible genotype AA and cardiovascular mortality (HR 1.08 95%CI 0.54 to 2.15) and all-cause mortality (HR 0.81 95%CI 0.27 to 2.43). Similar findings were observed for rs2416808 susceptible genotype GG in the non-RA cohort (HR 0.99; 95%CI 0.79 to 1.25 and HR 0.89; 95%CI 0.64 to 1.25, respectively). CONCLUSIONS: The TRAF1/C5 region is not associated with an increased mortality risk.

Association of a single-nucleotide polymorphism in CD40 with the rate of joint destruction in rheumatoid arthritis.

OBJECTIVE: The severity of joint destruction in rheumatoid arthritis (RA) is highly variable from patient to patient and is influenced by genetic factors. Genome-wide association studies have enormously boosted the field of the genetics of RA susceptibility, but risk loci for RA severity remain poorly defined. A recent meta-analysis of genome-wide association studies identified 6 genetic regions for susceptibility to autoantibody-positive RA: CD40, KIF5A/PIP4K2C, CDK6, CCL21, PRKCQ, and MMEL1/TNFRSF14. The purpose of this study was to investigate whether these newly described genetic regions are associated with the rate of joint destruction. METHODS: RA patients enrolled in the Leiden Early Arthritis Clinic were studied (n=563). Yearly radiographs were scored using the Sharp/van der Heijde method (median followup 5 years; maximum followup 9 years). The rate of joint destruction between genotype groups was compared using a linear mixed model, correcting for age, sex, and treatment strategies. A total of 393 anti-citrullinated protein antibody (ACPA)-positive RA patients from the North American Rheumatoid Arthritis Consortium (NARAC) who had radiographic data available were used for the replication study. RESULTS: The TT and CC/CG genotypes of 2 single-nucleotide polymorphisms, rs4810485 (CD40) and rs42041 (CDK6), respectively, were associated with a higher rate of joint destruction in ACPA-positive RA patients (P=0.003 and P=0.012, respectively), with rs4810485 being significant after Bonferroni correction for multiple testing. The association of the CD40 minor allele with the rate of radiographic progression was replicated in the NARAC cohort (P=0.021). CONCLUSION: A polymorphism in the CD40 locus is associated with the rate of joint destruction in patients with ACPA-positive RA. Our findings provide one of the first non-HLA-related genetic severity factors that has been replicated.