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To comprehensively analyze the overall incidence of hospitalization for comorbidities in patients with rheumatoid arthritis (RA). We prospectively analyzed overall hospitalizations for comorbidities using the Institute of Rheumatology, Rheumatoid Arthritis (IORRA) cohort. The incidence of hospitalized comorbidity was calculated. Risk factors for the most frequent hospitalized comorbidities were determined by multivariate logistic regression analysis. Among 5519 RA patients contributing 5336.5 person-years of observation, 435 incidences of hospitalized comorbidity [8.15/100 person-years; 95% confidence interval (CI) 7.40-8.95] were confirmed. The most frequent cause of hospitalized comorbidity was infection (1.52/100 person-years), primarily respiratory system infection (0.77/100 person-years), followed by malignancy (1.03/100 person-years), extra-articular manifestations (0.78/100 person-years), bone fracture (0.77/100 person-years), and acute coronary syndrome (0.22/100 person-years). Death occurred in 0.34/100 person-years (95% CI 0.20-0.53), and in 94.4% of cases the cause of death was the same as that of admission. The risk factors for the most frequent cause of hospitalization, hospitalized infection, were age [odds ratio (OR) 1.03; 95% CI 1.00-1.05], serum albumin level (OR 0.30; 95% CI 0.13-0.69), and corticosteroid use (prednisone > 5 mg/day; OR 3.66; 95% CI 1.81-7.35), but not methotrexate or biological agent use. The present study determined the overall burden of hospitalized comorbidities in patients with RA. These comprehensive data on hospitalized comorbidities may provide a basis for future improvements in the treatment of RA.

To our knowledge, no prior report focused on the risk factors for proximal humerus fractures in patients with rheumatoid arthritis. The purpose of this study was to evaluate the association between potential risk factors and the occurrence of proximal humerus fractures in patients with rheumatoid arthritis. A total of 11,907 patients with rheumatoid arthritis were enrolled in our observational cohort rheumatoid arthritis study between 2000 and 2012. Self-reported proximal humerus fractures were verified using the patients' medical records. Cox proportional hazard models were used to analyze the independent contribution of risk factors to the occurrence of proximal humerus fractures. During follow-up (mean 5.6 years), 92 proximal humerus fractures were verified in 91 patients. Multivariate Cox regression analyses estimated that the hazard ratios of sustaining a proximal humerus fracture were 1.37 for every 10-year increase in age [95 % confidence interval (CI) 1.10-1.70; P < 0.01], 1.95 for increases in serum C-reactive protein levels (mg/100 mL; 95 % CI 1.15-3.34; P < 0.05), 2.13 for a history of fractures (95 % CI 1.34-3.40; P < 0.01), 1.07 for the daily prednisolone dose (per mg; 95 % CI 1.01-1.13; P < 0.05), and 1.97 for oral bisphosphonate use (95 % CI 1.20-3.23; P < 0.01). Better control of rheumatoid arthritis with a smaller daily prednisolone dose in elderly patients with a history of fractures may be important for preventing proximal humerus fractures.

We investigated the effect of long-term corticosteroid usage in suppressing the progression of functional disability in patients with early rheumatoid arthritis (RA). We studied 3,982 RA patients, who had continuous enrollment for at least 3 years, among 9,132 RA patients enrolled in an observational cohort study, IORRA, in Tokyo, Japan, from 2000 to 2007. The DAS28 and Japanese version of Health Assessment Questionnaire (J-HAQ) scores were collected at 6-month intervals (each phase). Among these patients, those with DAS28 values under 3.2 in all phases and RA disease duration under 2 years at study entry were selected as "early RA patients with well-controlled disease". These patients were further classified into 3 groups based on average months of steroid usage per year: Non-users, Medium-users, and Frequent-users. Multiple linear regression analysis was used to study the relationship between steroid usage and the final J-HAQ scores. Among the 3,982 patients, 109 had DAS28 values under 3.2 in all the phases and were selected as study cohort. The average Final J-HAQ in Non-user (N = 64), in Medium-user (N = 25), in Frequent-user group (N = 20) was 0.04, 0.06, and 0.33, respectively. Multiple linear regression analysis after adjusting for all potential covariates confirmed that frequent steroid usage was the most significant factor associated with higher final J-HAQ scores (P < 0.05). Frequent steroid usage was associated with significantly higher final J-HAQ scores in early RA patients, even though their disease was managed efficiently by maintaining the DAS28 values under 3.2 over a long-term period.

To clarify the clinical significance of anti-cyclic citrullinated peptide antibody (anti-CCP) in the long-term outcome of RA, we established a large observational cohort of RA patients (IORRA) in our institute beginning in 2000. Essentially all RA patients who consulted our institute were registered, and clinical parameters, including disease activity and drug use, were assessed biannually based on patient reports, physician examinations, and laboratory data. In the third phase (October 2001) of the IORRA survey, anti-CCP levels were measured in 1,226 RA patients. In a cross-sectional analysis, clinical variables were compared in anti-CCP-positive versus -negative patients and in RF-positive versus -negative patients. In a longitudinal analysis, subsequent progression of disability was analyzed in anti-CCP-positive versus -negative and in RF-positive versus -negative patients. A verified Japanese version of the Health Assessment Questionnaire (J-HAQ) was used to measure functional disability. In the cross-sectional analysis, anti-CCP-positive patients (84.2%) had a significantly longer disease duration and higher disease activity score and more frequently used corticosteroids and methotrexate compared to anti-CCP-negative patients statistically. Similar phenomena were noted between RF-positive and -negative patients. In contrast, the longitudinal analysis revealed that J-HAQ slopes-a measure of progression of functional disability-were strongly associated with anti-CCP positivity but not with RF positivity. In a linear regression model, J-HAQ scores significantly worsened in anti-CCP-positive patients compared to anti-CCP-negative patients at the third year (annual progression 0.0317, P = 0.001) and the fifth year (annual progression 0.0199, P = 0.0012); however, J-HAQ progression was not influenced by RF status. Anti-CCP is a better predictive and discriminative marker for progression of disability in the long-term outcome of RA patients compared to RF.

To determine the incidence of malignancy and site-specific malignancies in Japanese patients with rheumatoid arthritis (RA). In a prospective large observational cohort study named IORRA, 7,566 patients with RA were enrolled from April 2001 to April 2005 and were followed up to October 2005. Occurrence of malignancy was originally collected by patient reports of IORRA survey biannually from April 2001 to October 2005, and was confirmed by medical records. Standardized incidence rate (SIR) of the observed-to-expected cancer incidence and 95% confidence intervals (95% CI) were then calculated. Factors obtained at first enrollment in IORRA were assessed for association with risk of malignancy using the Cox proportional hazards model. A total of 177 malignancies in 173 patients (58 in men, 115 in women) were identified during the observation period of 25,567 person-years. The age- and sex-standardized incidence rate of malignancy was 437.1 (men, 706.8; women, 366.1) per 100,000 person-years. The SIR of malignancy was slightly excess (SIR 1.18, [95% CI 1.02-1.37]) in all patients, but 1.29 (95% CI 0.99-1.67) in men, and 1.13 (95% CI 0.94-1.36) in women. A significant excess of lymphoma (SIR 6.07, [95% CI 3.71-9.37]) and lung cancer (SIR 2.29, [95% CI 1.57-3.21]), whereas decreased incidence of colorectal cancer (SIR 0.49, [95% CI 0.26-0.83]), were found. Male gender and older age were identified as risk factors for malignancy. A slight excess in the incidence of overall malignancy and highly excess of lymphoma in Japanese RA patients was demonstrated.

The anti-cyclic citrullinated peptide (CCP) antibody has become increasingly important in the diagnosis of rheumatoid arthritis (RA), especially for early diagnosis. The purpose of this study is to compare the diagnostic usefulness of the second and third generation anti-CCP antibody kits among Japanese patients with RA. Anti-CCP antibody titers were measured with the second generation (MESACUP CCP test, Medical and biological laboratories) and third generation (QUANTA Lite CCP3 IgG ELISA, Inova Diagnostics) kits using serum samples from 106 rheumatoid arthritis (RA) patients and 57 non-RA patients. Sensitivities and specificities were compared. The sensitivity and specificity of the second generation anti-CCP (anti-CCP2) kit were 88.7 and 89.5%, and those of the third generation anti-CCP (anti-CCP3) kit were 91.5 and 87.7%. Area under the receiver operating curve showed that anti-CCP2 and anti-CCP3 had similar diagnostic performances. Diagnostic performance of the anti-CCP3 assay was comparable with the anti-CCP2 assay in Japanese patients with RA.