Peter Docherty

Immunochip Analysis Identifies Multiple Susceptibility Loci for Systemic Sclerosis

In this study, 1,833 systemic sclerosis (SSc) cases and 3,466 controls were genotyped with the Immunochip array. Classical alleles, amino acid residues, and SNPs across the human leukocyte antigen (HLA) region were imputed and tested. These analyses resulted in a model composed of six polymorphic amino acid positions and seven SNPs that explained the observed significant associations in the region. In addition, a replication step comprising 4,017 SSc cases and 5,935 controls was carried out for several selected non-HLA variants, reaching a total of 5,850 cases and 9,401 controls of European ancestry. Following this strategy, we identified and validated three SSc risk loci, including DNASE1L3 at 3p14, the SCHIP1-IL12A locus at 3q25, and ATG5 at 6q21, as well as a suggested association of the TREH-DDX6 locus at 11q23. The associations of several previously reported SSc risk loci were validated and further refined, and the observed peak of association in PXK was related to DNASE1L3. Our study has increased the number of known genetic associations with SSc, provided further insight into the pleiotropic effects of shared autoimmune risk factors, and highlighted the power of dense mapping for detecting previously overlooked susceptibility loci.

A comparison of the frequency of antibodies to cyclic citrullinated peptides using a third generation anti-CCP assay (CCP3) in systemic sclerosis, primary biliary cirrhosis and rheumatoid arthritis

The objective was to investigate the frequency of anti-cyclic citrullinated peptides (CCP) antibodies in systemic sclerosis (SSc) and primary biliary cirrhosis (PBC), utilizing a new “third generation” anti-CCP ELISA (anti-CCP3) kit and a conventional anti-CCP2 assay. Patients with PBC, SSc, RA, and normal controls were included in the study. Serum samples were screened for autoantibodies by indirect immunofluorescence (IIF), antibodies to CCP by a second- and third-generation ELISA, antibodies to “scleroderma” antigens (CENP B, Scl-70, PM/Scl and fibrillarin—Scl-34) by a line immunoassay (LIA), and IgM RF by ELISA. The frequency of anti-CCP2 antibodies in SSc and PBC samples was 14.8% (11/74) and 6.2% (5/80), respectively, and the frequency of anti-CCP3 antibodies in SSc was 13.5% (10/74) and in PBC was 3.7% (3/80). By comparison, in the RA group the frequency of anti-CCP3 and anti-CCP2 antibodies was 79.1% (38/48) and 77% (37/48), respectively. Anti-CCP3 ELISA had a sensitivity, specificity, and positive and negative likelihood ratios (LR) of 79% (95% confidence interval [CI] = 64–89%), 93% (95% CI = 88–96%), 11.8 (95% CI = 6.8–20.3), and 0.22 (95% CI = 0.12–0.38), respectively. By comparison, the anti-CCP2 assay had a sensitivity, specificity, and positive and negative LRs of 77% (95% CI = 62–87), 90% (95% CI = 85–94), 8.3 (95% CI = 5.2–13.2), and 0.25 (95% CI = 0.15–0.42), respectively. In patients with SSc, there was an association of anti-CCP2 antibodies with the presence of arthritis, but there was no association of anti-CCP2 or anti-CCP3 with anti-CENP B, anti-Scl 70, or RF. This study confirmed the high specificity and sensitivity of both anti-CCP assays for the diagnosis of RA. The presence of anti-CCP antibodies in SSc was only correlated with the presence of arthritis.

2013 American College of Rheumatology/European League Against Rheumatism Classification Criteria for Systemic Sclerosis Outperform the 1980 Criteria: Data From the Canadian Scleroderma Research Group

The goal of this study was to determine the sensitivity of the new 2013 classification criteria for systemic sclerosis (SSc; scleroderma) in an independent cohort of SSc subjects and to assess the contribution of individual items of the criteria to the overall sensitivity.

Anti-Fibrillarin Antibody in African American Patients with Systemic Sclerosis: Immunogenetics, Clinical Features, and Survival Analysis

Objective. Anti-U3-RNP, or anti-fibrillarin antibodies (AFA), are detected more frequently among African American (AA) patients with systemic sclerosis (SSc) compared to other ethnic groups and are associated with distinct clinical features. We examined the immunogenetic, clinical, and survival correlates of AFA in a large group of AA patients with SSc. Methods. Overall, 278 AA patients with SSc and 328 unaffected AA controls were enrolled from 3 North American cohorts. Clinical features, autoantibody profile, and HLA class II genotyping were determined. To compare clinical manifestations, relevant clinical features were adjusted for disease duration. Cox proportional hazards regression was used to determine the effect of AFA on survival. Results. Fifty (18.5%) AA patients had AFA. After Bonferroni correction, HLA-DRB1*08:04 was associated with AFA, compared to unaffected AA controls (OR 11.5, p < 0.0001) and AFA-negative SSc patients (OR 5.2, p = 0.0002). AFA-positive AA patients had younger age of disease onset, higher frequency of digital ulcers, diarrhea, pericarditis, higher Medsger perivascular and lower Medsger lung severity indices (p = 0.004, p = 0.014, p = 0.019, p = 0.092, p = 0.006, and p = 0.016, respectively). After adjustment for age at enrollment, AFA-positive patients did not have different survival compared to patients without AFA (p = 0.493). Conclusion. Our findings demonstrate strong association between AFA and HLA-DRB1*08:04 allele in AA patients with SSc. AA SSc patients with AFA had younger age of onset, higher frequency of digital ulcers, pericarditis and severe lower gastrointestinal involvement, but less severe lung involvement compared to AA patients without AFA. Presence of AFA did not change survival.

The relationship of dyspnoea to function and quality of life in systemic sclerosis

Aim: Up to 50% of patients with systemic sclerosis (SSc) have complaints of dyspnoea. We evaluated the independent contributions of dyspnoea to function and health related quality of life (HRQoL) in SSc and also assessed the contributions of pulmonary hypertension, measured by the pulmonary artery systolic pressure (PASP), and interstitial lung disease, measured by the forced vital capacity (FVC), to dyspnoea. Methods: We assessed dyspnoea, PASP, FVC, function and HRQoL in a cohort of unselected patients with SSc. Multiple linear regression was used to assess the independent contributions of dyspnoea, PASP and FVC to function and HRQoL, after controlling for possible confounding variables. Results: A total of 194 patients with mean disease duration of 11.6 years were studied. Dyspnoea was a significant independent predictor of function and HRQoL. A model including age, gender, disease duration, disease severity and dyspnoea explained 33.3%, 10.6%, 39.2% and 29.4% of the variance of the Stanford Health Assessment Questionnaire, the Short-Form 36 (SF-36) mental component summary score, the SF-36 physical component summary score and the World Health Organization Disability Assessment Schedule II. PASP and FVC were significant independent predictors of dyspnoea but only 21.9% of the variance in dyspnoea was explained by age, gender, disease duration, FVC and PASP. The FVC was a significant independent predictor of function and HRQoL. Conclusion: In an unselected population of SSc patients, dyspnoea is a very important contributor to function and HRQoL. Interstitial lung disease, as measured by the FVC, contributes significantly to the sense of dyspnoea, function and HRQoL in SSc. Pulmonary hypertension, assessed echocardiographically by the PASP, predicts the degree of dyspnoea but not function and HRQoL in SSc.

Antinuclear antibody-negative systemic sclerosis.

OBJECTIVE To examine the demographic and clinical characteristics of systemic sclerosis (SSc) patients without antinuclear antibodies (ANA) compared to ANA-positive patients. METHODS SSc patients enrolled in the Scleroderma Family Registry and DNA Repository were included. Relevant demographic and clinical data were entered by participating sites or obtained by chart review. ANA and SSc-related antibodies were determined in all investigated patients using commercially available kits at our laboratories. RESULTS This study included 3249 patients, of whom 208 (6.4%) were ANA negative. The proportion of male patients was higher in the ANA-negative group (OR = 1.65; p = 0.008). ANA-negative patients experienced less vasculopathic manifestations of SSc. The percent predicted diffusing capacity of carbon monoxide (DLCO) was higher in ANA-negative patients (p = 0.03). Pulmonary arterial hypertension (PAH) per right heart catheterization was less common in the ANA-negative group (OR = 0.28; p = 0.03). Furthermore, patients with negative ANA had a lower prevalence of telangiectasias and digital ulcers/pits (OR = 0.59, p = 0.03 and OR = 0.38, p = 0.01, respectively). Although diffuse cutaneous involvement was more common, the modified Rodnan Skin Score (mRSS) was lower in the ANA-negative group (2.4 points lower, p = 0.05). Furthermore, they experienced more malabsorption (p = 0.05). There was no difference in the frequency of pulmonary fibrosis or scleroderma renal crisis. All-cause mortality was not different between the 2 groups (p = 0.28). CONCLUSIONS In conclusion, the results of this study suggest that SSc patients who are ANA negative constitute a distinct subset of SSc with less vasculopathy (less PAH, digital ulcers, and fewer telangiectasias), a greater proportion of males, and possibly, more frequent lower gastrointestinal involvement.

Reports of abnormal cervical cancer screening tests in systemic sclerosis

OBJECTIVE To assess the prevalence of abnormal cervical cancer screening (Pap tests) reported by women with SSc onset before the age of 50 yrs. METHODS Female members of a Canadian multi-centre SSc cohort completed standardized assessments and were questioned regarding a history of an abnormal Pap test. Potential correlates examined included demographics, reproductive history, smoking, diffuse vs limited SSc type, immunosuppressant exposure and SSc duration. RESULTS In the 320 women with SSc onset before the age of 50 yrs, the life-time prevalence of an abnormal Pap test (according to self-report) was 25.4% (95% CI CI 20.9, 30.4%). By comparison, self-reported prevalence of abnormal Pap tests among general population Canadian females was recently reported at 13.8% (95% CI 11.6, 16.4%). Women with diffuse SSc (n = 142), tended to have a higher prevalence of self-reported cervical dysplasia (31.7%) compared with those with limited disease (20.7%), but the CIs overlapped. A multivariate logistic regression found a significant positive association between self-reported abnormal Pap test and diffuse disease [odds ratio (OR) 1.87; 95% CI 1.01, 3.47]. An independent association of an abnormal Pap test with smoking (OR 2.43; 95% CI 1.23, 4.78) and with younger age at disease onset was also noted. CONCLUSIONS We noted a high prevalence of abnormal Pap tests self-reported in our sample. Increased risk was seen among those with diffuse SSc, and also among smokers and those with a younger age at disease onset. Thus, it seems prudent to ensure that adequate attention is paid to cervical cancer screening for women with SSc.

Assessment of Reproductive History in Systemic Sclerosis

OBJECTIVE To assess the number of live births in women whose systemic sclerosis (SSc) onset occurred during their reproductive years, and to compare this with general population rates. METHODS Within the Canadian Scleroderma Research Group cohort, we identified 320 women whose SSc symptoms began prior to age 50 years. We determined the number of children born in the years following first onset of symptoms. We summed the years of followup from the time of first symptoms in subjects up to age 50 years (or oldest age attained, if the subject was age <49 years). We applied age-specific birth rates for Canadian women to these years of followup in order to determine the expected number of live births for the period. We then calculated the standardized incidence ratio (SIR) of observed to expected live births. RESULTS In the 320 women studied, the number of live births over the interval since symptom onset was below the expected number (111 live births observed versus 140 expected; SIR 0.79, 95% confidence interval [95% CI] 0.65-0.95). This finding was more prominent in women with diffuse cutaneous disease versus limited cutaneous disease. The mean and median numbers of live births were similar across SSc subgroups based on organ involvement or cyclophosphamide exposure. In repeat analyses, including the reproductive period before SSc symptom onset, the ratio of observed to expected births was 1.23 (95% CI 1.13-1.33). CONCLUSION Compared with the general population, fewer live births were noted in women with SSc, but this phenomenon was only apparent in the period after symptom onset.

Genetic susceptibility loci of idiopathic interstitial pneumonia do not represent risk for systemic sclerosis: a case control study in Caucasian patients.

BackgroundSystemic sclerosis (SSc)-related interstitial lung disease (ILD) has phenotypic similarities to lung involvement in idiopathic interstitial pneumonia (IIP). We aimed to assess whether genetic susceptibility loci recently identified in the large IIP genome-wide association studies (GWASs) were also risk loci for SSc overall or severity of ILD in SSc.MethodsA total of 2571 SSc patients and 4500 healthy controls were investigated from the US discovery GWAS and additional US replication cohorts. Thirteen IIP-related selected single nucleotide polymorphisms (SNPs) were genotyped and analyzed for their association with SSc.ResultsWe found an association of SSc with the SNP rs6793295 in the LRRC34 gene (OR = 1.14, CI 95 % 1.03 to 1.25, p value = 0.009) and rs11191865 in the OBFC1 gene (OR = 1.09, CI 95 % 1.00 to 1.19, p value = 0.043) in the discovery cohort. Additionally, rs7934606 in MUC2 (OR = 1.24, CI 95 % 1.01 to 1.52, p value = 0.037) was associated with SSc-ILD defined by imaging. However, these associations failed to replicate in the validation cohort. Furthermore, SNPs rs2076295 in DSP (β = -2.29, CI 95 % -3.85 to -0.74, p value = 0.004) rs17690703 in SPPL2C (β = 2.04, CI 95 % 0.21 to 3.88, p value = 0.029) and rs1981997 in MAPT (β = 2.26, CI 95 % 0.35 to 4.17, p value = 0.02) were associated with percent predicted forced vital capacity (FVC%) even after adjusting for the anti-topoisomerase (ATA)-positive subset. However, these associations also did not replicate in the validation cohort.ConclusionsOur results add new evidence that SSc and SSc-related ILD are genetically distinct from IIP, although they share phenotypic similarities.

Demographic and Clinical Factors Associated with Physician Service Use in Systemic Sclerosis

Objective. To assess physician service use in a large sample of patients with systemic sclerosis (SSc), and to determine factors associated with physician use. Methods. Our sample was a national SSc registry maintaining data on demographics (age, sex, race/ethnicity, education, income) and clinical factors (disease onset, organ involvement, etc.). Registry cohort members completed detailed questionnaires, and rheumatologists provided clinical assessments. We examined cross-sectional data from 397 patients who provided information on physician visits in the past 12 months. Patients were classified as high physician-users if they reported more than the median number (6) of physician visits in the past year. In multivariate logistic regressions, we assessed the independent effects of race/ethnicity, education, degree of skin involvement, comorbidity, and SF-36 scores on physician use. Results. On average, subjects reported 3.8 visits per year to specialty physicians (SD 4.2) and 3.5 visits per year to family physicians (SD 4.3). Regression models suggested the following factors as independently associated with number of physician visits: high skin scores, greater comorbidity, and low physical component summary scores on the SF-36. Conclusion. There is evidence of independent relationships between clinical characteristics and physician use by patients with SSc.