Validity of clinical psoriatic arthritis diagnoses made by rheumatologists in the Swedish National Patient Register.

OBJECTIVES: : Knowledge of the correspondence between clinical ICD diagnoses and classification criteria fulfilment is crucial to interpret studies identifying cases via ICD codes. We assessed the degree to which patients registered with ICD-10 diagnoses of psoriatic arthritis (PsA) in the Swedish National Patient Register (NPR) fulfil established PsA classification criteria. METHOD: Four hundred patients with at least one outpatient visit to one of five rheumatology or internal medicine departments (three university/two county departments across Sweden) in 2013-2015, with a main ICD-10 diagnosis of PsA (L40.5, M07.0-M07.3), were randomly selected (80 cases/site). Through a structured medical record review, positive predictive values (PPVs) for fulfilment of the following classification criteria were assessed: CASPAR, Moll and Wright, Vasey and Espinoza, and modified ESSG criteria for PsA. A subset analysis regarding CASPAR fulfilment was also performed among cases with available rheumatoid factor and peripheral X-ray status (central CASPAR items; n = 227). RESULTS: Of the 400 patients with a main ICD-10 diagnosis of PsA, 343 (86%) fulfilled at least one of the four PsA classification criteria. PPVs for the different criteria were: CASPAR 69% (82% in the subset analysis), Moll and Wright 51%, Vasey and Espinoza 76%, and modified ESSG 64%. Overall, only 6.5% of the 400 PsA diagnoses were judged as clearly incorrect by the medical record reviewers. CONCLUSION: The validity of rheumatologist-made, clinical ICD-10 diagnoses for PsA in the Swedish NPR is good, with PPVs of 69-82% for CASPAR fulfilment and 86% for meeting any established PsA classification criteria.

Validation and characterization of venous thromboembolism diagnoses in the Swedish National Patient Register among patients with rheumatoid arthritis.

OBJECTIVE: To assess the validity of venous thromboembolism (VTE) diagnoses registered in the Swedish National Patient Register (NPR) in patients with rheumatoid arthritis (RA). METHOD: We performed a validation study using manual chart reviews to validate ICD-10 codes for VTE from the NPR. We took a random sample of 269 VTE events registered at hospitals in Region Stockholm from 2009 to 2018 in patients with RA. RESULTS: Medical records for all 269 VTE events were available for review. Overall, the positive predictive value (PPV) for a VTE diagnosis was 95%. For incident VTE events, the PPV was 87% and ranged from 80% to 98% across six more or less restricted alternative definitions of incident VTE event. Out of 235 confirmed incident VTE events, the vast majority were diagnosed independently of the RA disease (three cases occurred as a result of clinical work-up for a presumed RA-related sign or symptom, and in 17 cases did the work-up involve a rheumatologist). CONCLUSIONS: This study demonstrates high validity for VTE diagnoses recorded in the NPR for patients with RA, thus confirming that the NPR may be used to identify prevalent VTE as well as incident VTE events in patients with RA. Our results further demonstrate that in patients with RA, diagnoses of VTE are only marginally influenced by work-up related to the rheumatic disease, suggesting a modest impact of surveillance or diagnostic bias.

Social stressors and risk of rheumatoid arthritis and their relationship to known modifiable risk factors: results from the Swedish EIRA study.

Objectives: To investigate whether low social support or low decision latitude at work correlate with risk of rheumatoid arthritis (RA), and whether and how those factors are associated with known modifiable risk factors for RA.Method: The Swedish population-based EIRA study included, from 1996 to 2015, 3724 incident RA cases and 5935 controls, matched for age, gender, and residential area. Participants filled in detailed questionnaires at diagnosis. Using logistic regression, we investigated whether low social support and low decision latitude at work were associated with RA risk, and whether and how these exposures are associated with known modifiable risk factors for RA.Results: Low decision latitude at work was associated with RA risk in unadjusted analyses [odd ratio (OR) = 1.52, 95% confidence interval (CI) = 1.20-1.94], but this association was weakened after adjustment for known RA risk factors (adjusted OR = 1.24, 95% CI = 0.93-1.63). Low social support was not associated with RA risk (unadjusted OR = 1.05, 95% CI = 0.95-1.15). Cases reporting low decision latitude were more often smokers (OR = 2.05, 95% CI = 1.33-3.16), without university degrees (OR = 8.23, 95% CI = 5.13-13.22), and more often female (OR = 2.52, 95% CI = 1.66-3.81), with a similar pattern among controls. Cases reporting low social support were more often men (OR = 1.60, 95% CI = 1.40-1.83), smokers (OR = 1.46, 95% CI = 1.26-1.70), obese (OR = 1.29, 95% CI = 1.09-1.54), physically inactive (OR = 2.78, 95% CI = 1.98-3.90), and without university degrees (OR = 2.04, 95% CI = 1.77-2.36), with a similar pattern among controls.Conclusion: Low decision latitude coexisted with several known environmental/social risk factors for RA, together defining groups of individuals at increased risk of RA. These risk factors should be viewed in context when testing actions to diminish RA risk in prospective studies.

Population-based study of patients with primary Sjögren's syndrome and lymphoma: lymphoma subtypes, clinical characteristics, and gender differences.

Objective: To examine lymphoma subtypes, clinical characteristics, and gender differences in patients with primary Sjögren's syndrome (pSS) and lymphoma in a population-based setting.Method: Patients with Sjögren's syndrome and lymphoma diagnoses were identified by linkage of the Swedish Patient Register 1964-2007 with the Cancer Register 1990-2007. Clinical data were collected from medical records and lymphoma tissues were re-examined. The lymphoma subtype distribution was compared with the Swedish Lymphoma Register.Results: We identified 105 pSS patients with lymphoma. Diffuse large B-cell lymphoma (DLBCL) (32%) and marginal zone lymphoma [MZL including mucosa-associated lymphoid tissue (MALT) lymphoma] (31%) were the most common lymphoma subtypes. The proportion of DLBCL was not increased compared to the general population reference (32%, p = 1), in contrast to MZL (general population 5%, p < 0.0001). Compared to DLBCL, MALT lymphoma was diagnosed at a younger age (55 vs 67 years, p = 0.0001), and earlier after patient-reported sicca onset (7 vs 18 years, p = 0.0001) and pSS diagnosis (2 vs 9 years, p = 0.0005). Sixteen of the pSS-lymphoma cases were men (15%), twice the proportion in general pSS populations. Compared to women, men had a shorter median time from pSS diagnosis to lymphoma diagnosis (1 vs 8 years, p = 0.0003) and more often had lymphoma in the salivary glands (56% vs 29%, p = 0.04).Conclusion: DLBCL and MZL are common in pSS patients, but only MZL/MALT lymphoma occurs at an increased relative frequency in pSS compared to the general population. The study supports increased awareness of signs of lymphoma in men in the first years after pSS diagnosis.

Comparison of patients with and without pre-existing lymphoma at diagnosis of primary Sjögren's syndrome.

OBJECTIVE: In the 2016 American College of Rheumatology/European League Against Rheumatism classification criteria for primary Sjögren's syndrome (pSS), pre-existing lymphoma is not an exclusion criterion for pSS diagnosis, as in earlier criteria. We aimed to explore whether there are differences between pSS patients with and without pre-existing lymphoma at pSS diagnosis. METHOD: Patients with ICD-7-10 codes for Sjögren's syndrome (SS) and a diagnosis of malignant lymphoma before or after SS diagnosis were identified by linking the Swedish Patient Register 1964-2007 with the Cancer Register 1990-2007 (n = 224). Clinical data were collected from medical records. Lymphoma diagnoses were evaluated by tissue review. Characteristics of pSS patients with and without pre-existing lymphoma were compared. RESULTS: We identified 107 patients with pSS as the reason for an SS diagnosis code and a verified lymphoma. Of these, 18 (17%) had a pre-existing lymphoma at pSS diagnosis, defined as lymphoma diagnosed before or within 6 months of pSS diagnosis. Male gender (39% vs 10%, p = 0.006), enlarged lymph nodes during the pSS disease (61% vs 27%, p = 0.01), mucosa-associated lymphoid tissue (MALT) lymphoma (50% vs 22%, p = 0.02), and salivary gland lymphoma (61% vs 26%, p = 0.006) were more common in patients with a pre-existing lymphoma at pSS diagnosis. Other pSS characteristics were similar. CONCLUSION: In a substantial proportion of patients, particularly in men, pSS remains undiagnosed until after lymphoma diagnosis. The study highlights the importance of pSS investigation in patients with lymphoma, especially MALT lymphoma, in the salivary glands.

Biological treatment in ankylosing spondylitis in the Nordic countries during 2010-2016: a collaboration between five biological registries.

OBJECTIVES: Large-scale observational cohorts may be used to study the effectiveness and rare side effects of biological disease-modifying anti-rheumatic drugs (bDMARDs) in ankylosing spondylitis (AS), but may be hampered by differences in baseline characteristics and disease activity across countries. We aimed to explore the research infrastructure in the five Nordic countries regarding bDMARD treatment in AS. METHOD: This observational cohort study was based on data from biological registries in Denmark (DANBIO), Sweden (SRQ/ARTIS), Finland (ROB-FIN), Norway (NOR-DMARD), and Iceland (ICEBIO). Data were collected for the years 2010-2016. Registry coverage, registry inventory (patient characteristics, disease activity measures), and national guidelines for bDMARD prescription in AS were described per country. Incident (first line) and prevalent bDMARD use per capita, country, and year were calculated. In AS patients who started first line bDMARDs during 2010-2016 (n = 4392), baseline characteristics and disease activity measures were retrieved. RESULTS: Registry coverage of bDMARD-treated patients ranged from 60% to 95%. All registries included extensive prospectively collected data at patient level. Guidelines regarding choice of first line drug and prescription patterns varied across countries. During the period 2010-2016 prevalent bDMARD use increased (p < 0.001), whereas incident use tended to decrease (p for trend < 0.004), with large national variations (e.g. 2016 incidence: Iceland 10.7/100 000, Finland 1.7/100 000). Baseline characteristics were similar regarding C-reactive protein, but differed for other variables, including the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) (range 3.5-6.3) and Ankylosing Spondylitis Disease Activity Score (ASDAS) (2.7-3.8) (both p < 0.0001). CONCLUSION: Collaboration across the five Nordic biological registries regarding bDMARD use in AS is feasible but national differences in coverage, prescription patterns, and patient characteristics must be taken into account depending on the scientific question.

Anti-cyclic citrullinated peptide antibodies, other common autoantibodies, and smoking as risk factors for lymphoma in patients with rheumatoid arthritis.

OBJECTIVES: Patients with rheumatoid arthritis (RA) are at increased risk of lymphoma. There is no biomarker to indicate future lymphoma risk in RA and it is not known whether factors associated with an increased risk of RA also confer an increased risk of lymphoma. We investigated whether anti-cyclic citrullinated peptide (CCP) antibodies, other autoantibodies, and smoking, are associated with lymphoma development in RA. METHOD: From two population-based case-control studies, the Scandinavian Lymphoma Etiology (SCALE) study and the Epidemiological Investigation of Rheumatoid Arthritis (EIRA) I study, we identified lymphoma cases with a validated RA diagnosis (n = 50), to whom we matched study participants with RA but no lymphoma (n = 261), lymphoma but no RA (n = 257), and neither RA nor lymphoma (n = 233). Lymphomas were classified according to the WHO classification. Blood samples were analysed for immunoglobulin G (IgG), IgM, and IgA isotypes and IgG1-4 subclasses of anti-CCP antibodies and for 15 antinuclear antibody (ANA)-associated specific autoantibodies. Relative risks were estimated as crude and adjusted odds ratios (adjOR) with 95% confidence intervals (CIs) using logistic regression. RESULTS: We found no association between anti-CCP IgG ≥ 25 units/mL (adjOR 1.4, 95% CI 0.7-2.7), anti-CCP IgG ≥ 500 units/mL (adjOR 1.4, 95% CI 0.7-3.0), anti-CCP Ig of other isotypes, other autoantibodies (adjOR any vs none 0.6, 95% CI 0.3-1.2), or cigarette smoking (adjOR ever vs never 1.1, 95% CI 0.5-2.2) and lymphoma risk among patients with RA. CONCLUSION: In this study, neither anti-CCP antibodies (IgG, IgG1-4, IgM, or IgA), nor other common autoantibodies, nor smoking predicted lymphoma risk in RA.

Childhood onset inflammatory bowel disease and risk of cancer: a Swedish nationwide cohort study 1964-2014.

Objective To assess risk of cancer in patients with childhood onset inflammatory bowel disease in childhood and adulthood.Design Cohort study with matched general population reference individuals using multivariable Cox regression to estimate hazard ratios.Setting Swedish national patient register (both inpatient and non-primary outpatient care) 1964-2014.Participants Incident cases of childhood onset (<18 years) inflammatory bowel disease (n=9405: ulcerative colitis, n=4648; Crohn's disease, n=3768; unclassified, n=989) compared with 92 870 comparators from the general population matched for sex, age, birth year, and county.Main outcome measures Any cancer and cancer types according to the Swedish Cancer Register.Results During follow-up through adulthood (median age at end of follow-up 27 years), 497 (3.3 per 1000 person years) people with childhood onset inflammatory bowel disease had first cancers, compared with 2256 (1.5 per 1000 person years) in the general population comparators (hazard ratio 2.2, 95% confidence interval 2.0 to 2.5). Hazard ratios for any cancer were 2.6 in ulcerative colitis (2.3 to 3.0) and 1.7 in Crohn's disease (1.5 to 2.1). Patients also had an increased risk of cancer before their 18th birthday (2.7, 1.6 to 4.4; 20 cancers in 9405 patients, 0.6 per1000 person years). Gastrointestinal cancers had the highest relative risks, with a hazard ratio of 18.0 (14.4 to 22.7) corresponding to 202 cancers in patients with inflammatory bowel disease. The increased risk of cancer (before 25th birthday) was similar over time (1964-1989: 1.6, 1.0 to 2.4; 1990-2001: 2.3, 1.5 to 3.3); 2002-06: 2.9, 1.9 to 4.2; 2007-14: 2.2, 1.1 to 4.2).Conclusion Childhood onset inflammatory bowel disease is associated with an increased risk of any cancer, especially gastrointestinal cancers, both in childhood and later in life. The higher risk of cancer has not fallen over time.

Anti-TNF treatment in Crohn's disease and risk of bowel resection-a population based cohort study.

BACKGROUND: TNF inhibitors (TNFi) have been shown to reduce the need for surgery in Crohn's disease, but few studies have examined their effect beyond the first year of treatment. AIM: To conduct a register-based observational cohort study in Sweden 2006-2014 to investigate the risk of bowel resection in bowel surgery naïve TNFi-treated Crohn's disease patients and whether patients on TNFi ≥12 months are less likely to undergo bowel resection than patients discontinuing treatment before 12 months. METHODS: We identified all individuals in Sweden with Crohn's disease through the Swedish National Patient Register 1987-2014 and evaluated the incidence of bowel resection after first ever dispensation of adalimumab or infliximab from 2006 and up to 7 years follow-up. RESULTS: We identified 1856 Crohn's disease patients who had received TNFi. Among these patients, 90% treatment retention was observed at 6 months after start of TNFi and 65% remained on the drug after 12 months. The cumulative rates of surgery in Crohn's disease patients exposed to TNFi years 1-7 were 7%, 13%, 17%, 20%, 23%, 25% and 28%. Rates of bowel resection were similar between patients with TNFi survival <12 months and ≥12 months respectively (P=.27). No predictors (eg, sex, age, extension or duration of disease) for bowel resection were identified. CONCLUSIONS: The risk of bowel resection after start of anti-TNF treatment is higher in regular health care than in published RCTs. Patients on sustained TNFi treatment beyond 12 months have bowel resection rates similar to those who discontinue TNFi treatment earlier.

Prevalence of paediatric inflammatory bowel disease in Sweden: a nationwide population-based register study.

BACKGROUND: We evaluated the impact of different case definition algorithms on the prevalence of paediatric inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis (UC) and to compare the occurrence of certain diseases compared to matched controls. METHODS: Paediatric patients (<18 years) were identified via ICD codes for UC and CD in Swedish registers between 1993 and 2010 (n = 1432). Prevalence was defined as ≥2 IBD-related visits. Prevalence of treated children in 2010 was defined as ≥2 IBD-related visits with one visit and ≥1 dispensed IBD-related drug prescription in 2010. To test the robustness of the estimates, prevalence was also calculated according to alternative case definitions. The presence of rheumatic, hepatobiliary, pancreatic, and dermatologic diseases were compared with age-/sex-/county-of-residence-matched general population controls. RESULTS: The IBD prevalence was 75/100,000 (CD: 29/100,000; UC: 30/100,000; patients with IBD-U: 16/100,000). Prevalence of treated disease in 2010 was 62/100,000 (CD: 23/100,000; UC: 25/100,000; patients with IBD-U: 13/100,000). When age restrictions were employed, the prevalence estimate decreased (<17y: 61/100,000, <16y: 49/100,000 and <15y: 38/100,000). Compared to general population controls (n = 8583), children with IBD had a higher prevalence of dermatologic (4.7% vs. 0.6%), hepatobiliary (including primary sclerosing cholangitis) (5.5% vs. 0.1%), pancreatic (1.7% vs. 0%) and rheumatic diseases (7.2% vs. 1.2%; all P < 0.01). CONCLUSIONS: The overall prevalence of paediatric IBD in Sweden was similar to that in earlier regional cohorts. IBD patients had a higher prevalence of comorbid conditions than matched general population controls.

Predictors of work disability after start of anti-TNF therapy in a national cohort of Swedish patients with rheumatoid arthritis: does early anti-TNF therapy bring patients back to work?

OBJECTIVES: To examine predictors of work ability gain and loss after anti-tumour necrosis factor (TNF) start, respectively, in working-age patients with rheumatoid arthritis (RA) with a special focus on disease duration. METHODS: Patients with RA, aged 19-62 years, starting their first TNF inhibitor 2006-2009 with full work ability (0 sick leave/disability pension days during 3 months before bio-start; n=1048) or no work ability (90 days; n=753) were identified in the Swedish biologics register (Anti-Rheumatic Treatment In Sweden, ARTIS) and sick leave/disability pension days retrieved from the Social Insurance Agency. Outcome was defined as work ability gain ≥50% for patients without work ability at bio-start and work ability loss ≥50% for patients with full work ability, and survival analyses conducted. Baseline predictors including disease duration, age, sex, education level, employment, Health Assessment Questionnaire, Disease Activity Score 28 and relevant comorbidities were estimated using Cox regression. RESULTS: During 3 years after anti-TNF start, the probability of regaining work ability for totally work-disabled patients was 35% for those with disease duration <5 years and 14% for disease duration ≥5 years (adjusted HR 2.1 (95% CI 1.4 to 3.2)). For patients with full work ability at bio-start, disease duration did not predict work ability loss. Baseline disability pension was also a strong predictor of work ability gain after treatment start. CONCLUSIONS: A substantial proportion of work-disabled patients with RA who start anti-TNF therapy regain work ability. Those initiating treatment within 5 years of symptom onset have a more than doubled 3-year probability of regaining work ability compared with later treatment starts. This effect seems largely due to the impact of disease duration on disability pension status.

Rheumatoid Arthritis and Risk of Malignant Lymphoma: Is the Risk Still Increased?

OBJECTIVE: Patients with rheumatoid arthritis (RA) are at increased risk of malignant lymphomas with a strong correlation with RA disease severity. Given the changes in RA therapy over recent decades, this study was undertaken to assess whether lymphoma risk remains increased, and if so, to explore risk predictors and lymphoma subtypes. METHODS: We identified 12,656 cases of incident RA in the Swedish Rheumatology Quality Register 1997-2012 and obtained information on therapy and inflammatory activity during the first year after diagnosis. Each patient was matched to 10 population comparator subjects. Through linkage to the Swedish Cancer Register, lymphomas, including subtypes, were identified. We assessed hazard ratios (HRs) using Cox regression. RESULTS: Overall, the HR for lymphoma was increased in RA, to 1.6 (95% confidence interval [95% CI] 1.2-2.1). Taking RA duration into account, risks did not appear to have declined over successive calendar years of RA diagnosis. Neither use of methotrexate the first year after RA diagnosis nor ever use of tumor necrosis factor inhibitors (TNFi) increased lymphoma risk (HR 0.9 [95% CI 0.4-1.9]). Use of oral corticosteroids the first year after RA diagnosis was associated with a reduced risk (HR 0.5 [95% CI 0.3-0.9]). Inflammatory activity during the first year after RA diagnosis did not predict future lymphoma risk. Chronic lymphocytic leukemia occurred less frequently, and Hodgkin's lymphoma occurred more frequently, in RA patients than in the general population. CONCLUSION: The average lymphoma risk in recently diagnosed RA is similar in magnitude to that reported in historical cohorts. Standard antirheumatic treatment including TNFi did not predict future lymphoma risk. Distribution of lymphoma subtypes warrants further investigation.

Comparative analysis of first-year fingolimod and natalizumab drug discontinuation among Swedish patients with multiple sclerosis.

BACKGROUND: Natalizumab (NTZ) and fingolimod (FGL) are mainly used second line in relapsing-remitting multiple sclerosis (MS), although pivotal trials included mainly treatment-naïve patients. OBJECTIVE: This study aims to provide real-world data on safety and discontinuation rates. METHODS: Using IMSE, a drug monitoring registry for all newer MS drugs in Sweden, we analysed differences in baseline characteristics and 1-year drug survival for patients registered 2011-2013, initiating treatment with NTZ (n=640) or FGL (n=876). Among FGL initiators, n=383 (44%) had previously used NTZ (FGL(afterNTZ)). RESULTS: Compared with NTZ, the FGL cohort was older and more often male (36/38 years, 24%/33% males). Baseline Expanded Disability Status Scale was similar across groups, but MS Severity Score was higher in NTZ patients, and Symbol Digit Modalities Test and MS Impact Scale (MSIS-29) was higher in FGL(afterNTZ) versus FGL(NTZ-naïve) patients. Proportion on drug after 1 year was high, NTZ=87%, FGL(NTZ-naïve)=83% and FGL(afterNTZ)=76%. Adverse events was the most frequent reason for discontinuing FGL (FGL(NTZ-naïve)=9%, FGL(afterNTZ)=12%), and was significantly higher than on NTZ (3%). In contrast, the proportion of patients stopping treatment due to lack of effect was more similar: NTZ=4%, FGL(NTZ-naïve)=3%, FGL(afterNTZ)=8%. CONCLUSION: FGL and NTZ were both well tolerated, but FGL less so than NTZ, especially in patients switching to FGL from NTZ. Group differences were not explained by differences in recorded baseline characteristics.

What is the impact of chronic systemic inflammation such as rheumatoid arthritis on mortality following cancer?

BACKGROUND: Emerging evidence links inflammation and immune competence to cancer progression and outcome. Few studies addressing cancer survival in the context of rheumatoid arthritis (RA) have reported reduced survival without accounting for the underlying mortality risk in RA. Whether this increased mortality is a cancer-specific phenomenon, an effect of the decreased lifespan in RA or a combination of both remains unknown. METHODS: Using Swedish register data (2001-2009), we performed a cohort study of individuals with RA (N=34 930), matched to general population comparators (N=169 740), incident cancers (N=12 676) and deaths (N=14 291). Using stratified Cox models, we estimated HRs of death associated with RA in the presence and absence of cancer, by stage and time since cancer diagnosis, for all cancers and specific sites. RESULTS: In the absence of cancer, RA was associated with a doubled mortality rate (HR=2.1, 95% CI 2.0 to 2.2). In the presence of cancer, the relative effect of RA on mortality was varied by stage. For cancer (tumour, node, metastases) stages I and II at diagnosis, the relative effect of RA on mortality was the same as in the absence of cancer. For cancers diagnosed at advanced stages with absolute higher mortality, the effect decreased (HR=1.2, 95% CI 1.1 to 1.3). These associations remained across time since cancer diagnosis and were reasonably similar across cancer sites. CONCLUSIONS: Much of the increase in mortality in patients with RA diagnosed with cancer seems to reside with effects of RA independently of the cancer.

Surgical interventions for nephrolithiasis in ankylosing spondylitis and the general population.

OBJECTIVE: The aim of this study was to estimate rates and type of definitive surgical interventions for nephrolithiasis in Swedish patients with ankylosing spondylitis (AS) compared to the general population. MATERIALS AND METHODS: This national prospective cohort study linked data from Swedish population and healthcare registries. Incidence rates and interventions for nephrolithiasis during follow-up in patients with AS were compared to general population comparator (GPC) subjects. RESULTS: In total, 8572 AS patients were followed for 49,959 person-years and 39,639 matched GPCs were followed for 225,221 person-years. Mean age at study entry was 46 years [interquartile range (IQR) 36-56 years] and 65% were male. In AS patients with a diagnosis of nephrolithiasis during the study period, 29% (72/250) underwent similar intervention for nephrolithiasis compared to 24% (114/466) GPCs (p = 0.21). The incidence rate ratio (RR) in overall AS patients was 2.9 [95% confidence interval (CI) 2.1-3.8] during a median follow-up of 6.2 years (IQR 3.2-8.6 years). With prior diagnosis of nephrolithiasis, the RR for AS patients compared to GPCs was 3.7 (95% CI 1.8-7.7); without prior nephrolithiasis the RR was 2.1 (95% CI 1.5-3.0). Increasing age [odds ratio (OR) 1.02, 95% CI 1.01-1.03], prior nephrolithiasis diagnosis (OR 3.3, 95% CI 1.97-5.62) and atherosclerotic cardiac disease (OR 2.0, 95% CI 1.03-3.91) were identified as predictors of intervention for nephrolithiasis. CONCLUSIONS: Patients with AS have an almost three-fold increased risk of surgical intervention for kidney stones, with similar management, compared to the general population.

Effectiveness and survival-on-drug of certolizumab pegol in rheumatoid arthritis in clinical practice: results from the national Swedish register.

OBJECTIVES: Evidence regarding the efficacy and effectiveness of certolizumab pegol (CZP) in rheumatoid arthritis (RA) patients who have failed to respond to treatment with a tumour necrosis factor inhibitor (TNFi) is limited. The aim of this study was to describe the effectiveness and survival-on-drug of CZP in a real-life setting, both in TNFi-naïve patients and in patients who had previously failed TNFis, and in relation to disease activity at baseline. METHOD: The national Swedish Rheumatology Quality Register (SRQ) was used to identify patients with RA starting treatment with CZP between 2009 and 2013. The effectiveness of treatment was assessed using the 28-joint Disease Activity Score (DAS28), the Health Assessment Questionnaire (HAQ), measures of remission, the European League Against Rheumatism (EULAR) response during 0-6 months from start of treatment, and survival-on-drug during the first 30 months. RESULTS: A total of 945 RA patients started treatment with CZP. Of these, 540 (57.1%) received CZP as the first biological treatment, 215 (23%) had failed one previous TNFi, and 190 (20%) had failed at least two TNFis. Overall, 71% achieved at least a EULAR moderate response and 38% had a EULAR good response at 6 months from baseline. TNFi-naïve patients achieved significantly better results and had better survival-on-drug compared to patients who had failed previous TNFis. Around 20% of patients who had not responded to two or more prior TNFis achieved EULAR good response to therapy and a similar percentage achieved remission. Patients who had high baseline disease activity had a higher risk of discontinuing treatment compared to those without high disease activity. CONCLUSIONS: In this real-life RA cohort, CZP was associated with significant clinical improvement. The effectiveness and survival-on-drug vary markedly depending on the line of treatment.

Validity of ankylosing spondylitis and undifferentiated spondyloarthritis diagnoses in the Swedish National Patient Register.

OBJECTIVES: Epidemiological studies of spondyloarthritis (SpA), using ICD codes from the Swedish National Patient Register (NPR), offer unique possibilities but hinge upon an understanding of the validity of the codes. The aim of this study was to validate the ICD codes for ankylosing spondylitis (AS) and undifferentiated SpA (uSpA) in the NPR against the established classification criteria [modified New York (mNY), Assessment of SpondyloArthritis international Society (ASAS), Amor, and European Spondyloarthropathy Study Group (ESSG) criteria]. METHOD: All patients with an ICD-8/9/10 code of AS or uSpA in the NPR 1966-2009 at a visit to a specialist in rheumatology or internal medicine or corresponding hospitalization, alive and living in Sweden 2009, were identified (n=20,089). Following a structured procedure to achieve geographical representativeness, 500 random patients with a diagnosis of AS or uSpA in 2007-2009 were selected. Based on a structured review of clinical records, positive predictive values (PPVs) for fulfilling the criteria sets were calculated. RESULTS: For those having received an ICD code for AS, the PPVs for fulfilling the mNY criteria or any set of SpA criteria were 70% and 89%, respectively. For those with an uSpA diagnosis (and never an AS diagnosis), the corresponding PPVs were 20% and 79%. The subset with both AS and uSpA diagnoses (overlap=12%) were as likely to fulfil the mNY criteria as the group that had been coded as AS only. CONCLUSIONS: The diagnosis codes for AS or uSpA had high PPVs, suggesting that our case identification in the Swedish NPR can be used for nationwide, population-based, epidemiological studies of these diseases.

Safety of Etoricoxib, Celecoxib, and Nonselective Nonsteroidal Antiinflammatory Drugs in Ankylosing Spondylitis and Other Spondyloarthritis Patients: A Swedish National Population-Based Cohort Study.

OBJECTIVE: Safety data regarding the use of etoricoxib and other nonsteroidal antiinflammatory drugs (NSAIDs) in ankylosing spondylitis (AS) and other spondyloarthritis (SpA) patients are rather limited. Our objective was to estimate and compare rates of gastrointestinal, renovascular, and cardiovascular adverse events in patients exposed to etoricoxib, celecoxib, or nonselective NSAIDs or totally unexposed to NSAIDs. METHODS: We performed a national register-based cohort study on patients with AS or SpA (n = 21,872) identified in the Swedish national patient register from 1987-2009. Treatment exposure was assessed time dependently based on the prescription drug register from 2006-2009, adjusting for sociodemographics and comorbidities derived from national population-based registers. RESULTS: Exposure to etoricoxib, celecoxib, and nonselective NSAIDs was 7.6%, 3.9%, and 71.2%, respectively. No major risk differences for serious cardiovascular, gastrointestinal, or renal adverse events were seen among the 3 exposure groups. Patients unexposed to NSAIDs had more baseline comorbidities and an increased relative risk for congestive heart failure events during the study period (2.0, 95% confidence interval [95% CI] 1.3-3.2). The relative risk for atherosclerotic events was nonsignificant when compared to the nonselective NSAID group (1.0, 95% CI 0.7-1.5), while the relative risk for gastrointestinal events was lower for unexposed patients (0.5, 95% CI 0.4-0.7). CONCLUSION: Overall, serious adverse events related to nonselective NSAIDs, etoricoxib, and celecoxib were similar and in the range of what would be expected in a group of SpA patients. Patients unexposed to NSAIDs had considerably more baseline comorbidities and increased risk for congestive heart failure, reflecting a selection of patients being prescribed NSAIDs in clinical practice.

The autoimmune spectrum of myasthenia gravis: a Swedish population-based study.

OBJECTIVES: To determine the prevalence of myasthenia gravis (MG) and the rate of concurrent autoimmune diseases in patients with MG. DESIGN AND SETTING: Using the Swedish health and population registers, during the period 2005-2010, we conducted a nested case-control study of patients with MG (n = 2045) with five age- and sex-matched population-based controls per case. Register-based MG diagnosis was validated against the Stockholm MG Cohort. Similar nested case-control studies were conducted in patients with multiple sclerosis (MS), as a neuroinflammatory disease control, and siblings of patients with MG. MAIN OUTCOME MEASURE: Odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated as a measure of the association between MG and other autoimmune diseases. RESULTS: The prevalence of MG was 24.8/100,000, and patients with MG had an increased risk of another autoimmune disease compared to controls (22.0% vs. 8.9%; OR: 2.82, 95% CI: 2.49-3.20); this risk was stronger amongst younger persons and women. Polymyositis/dermatomyositis, systemic lupus erythematosus and Addison's disease, three conditions regulated by the HLA-B8-DR3 haplotype, were most strongly associated with MG, especially early-onset disease. HLA typing in the Stockholm MG Cohort showed that early-onset MG was indeed dominated by HLA-B8-DR3. The risk of another autoimmune disease was increased in both patients with MS and siblings of patients with MG, compared to their respective controls, but to a lesser extent than in patients with MG. CONCLUSIONS: Our results suggest that MG shares risk factors with other autoimmune diseases, to a greater degree than MS, with a particular role of the HLA-B8-DR3 haplotype, especially amongst younger and female patients.