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This study revisits a central assumption of standard trade models: constant marginal cost technology. The presence of increasing marginal costs for exporters introduces significant market interdependence across borders missing from traditional models of international trade that rely on constant marginal cost technology. Such market interdependence represents an additional channel through which local shocks are transmitted globally. To identify increasing marginal cost at the level of the firm, we build in flexible production assumptions that nest increasing, decreasing, and constant marginal cost technology to an otherwise standard international trade model. We derive an estimating equation that can be taken directly to the data. Our structural equation explicitly guides our inference on the shape of the marginal cost curve from estimated coefficients. The results suggest that increasing marginal cost is predominant at the firm level. Moreover, utilizing plant-level information on physical and financial capacity constraints, we find that the degree of increasing marginal cost is significantly exacerbated by both types of constraints. The evidence suggests that access to larger markets through greater international integration may not have the expected welfare gains typically predicted in standard models. (JEL F12, F14)

Objective Measuring physical activity in people with rheumatoid arthritis (RA) is of great importance in light of the increased mortality in this population due to cardiovascular disease. Validation of activity monitors in specific populations is recommended to ensure the accuracy of physical activity measurement. Thus, the purpose of this study was to determine the validity of the SenseWear Pro3 Armband (SWA) as a measure of physical activity during activities of daily living (ADL) in people with RA. Methods Fourteen subjects (8 men and 6 women) with a diagnosis of RA were recruited from rheumatology clinics at the Mid-Western Regional Hospitals, Limerick, Ireland. Participants undertook a series of ADL of varying intensities. The SWA was compared to the criterion measures of the Oxycon Mobile indirect calorimetry system (energy expenditure in kJ) and of manual video observation (step count). Bland and Altman, intraclass correlation coefficient (ICC), and correlation analyses were done using SPSS, version 19.0. Results The SWA showed substantial agreement (ICC 0.717, P < 0.001) and a strong relationship (Pearson's correlation coefficient = 0.852) compared with the criterion measure when estimating energy expenditure during ADL. However, it was found that the SWA overestimated energy expenditure, particularly at higher intensity levels. The ability of the SWA to estimate step counts during ADL was poor (ICC 0.304, P = 0.038). Conclusion The SWA can be considered a valid tool to estimate energy expenditure during ADL in the RA population; however, attention should be paid to its tendency to overestimate energy expenditure.

Objectives The aim of the present study was to qualitatively explore users' experiences of home monitoring of health with specific regard to physical activity monitors. Methods Fourteen participants were randomly selected from a larger sample of individuals with rheumatoid arthritis (RA) who had taken part in a physical activity monitoring study and had worn two physical activity monitors for seven days in their homes. These individuals were assigned to one of two focus groups. Each focus group lasted for between 40 minutes and an hour and was audio-recorded. A semi-structured questioning route was used, followed by subsequent theoretical thematic analysis. Results No statistically significant differences were noted in the demographic factors between those who took part in the focus groups and the entire RA sample. Three distinct themes were identified: i) Experiences of having health monitored in the home, which was found to be largely positive; ii) Experiences of use of specific technology to monitor physical activity, which was generally reported as unobtrusive and not to impact significantly negatively on their daily life; iii) Perceptions and experiences of physical activity and exercise, which monitoring was reported to facilitate focusing on physical activity choices. Conclusions These focus groups were the first to highlight the perceptions held by individuals with RA regarding home monitoring and, in particular, physical activity monitoring. This has implications for those planning interventions for this group which involve home monitoring. Interesting findings were also highlighted regarding the perceptions and understanding of physical activity and exercise among people with RA. Copyright © 2012 John Wiley & Sons, Ltd.

Objective To evaluate the efficacy of infliximab in HLA–B27–positive patients with magnetic resonance imaging (MRI)–determined early sacroiliitis, using both clinical and MRI assessments. Methods Forty patients with recent-onset inflammatory back pain, as assessed by the Calin criteria, HLA–B27 positivity, clinical disease activity as measured by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), pain and morning stiffness, and magnetic resonance imaging (MRI)–determined sacroiliac joint bone edema were randomized in a double-blind manner to receive infliximab 5 mg/kg or placebo at 0, 2, 6, and 12 weeks. MRI scans were performed at baseline and 16 weeks and scored by 2 observers (blinded to both the order of the scans and to treatment group), using the Leeds scoring system. Clinical assessments included the BASDAI, the Bath Ankylosing Spondylitis Functional Index (BASFI), the Ankylosing Spondylitis Quality of Life (ASQoL) instrument, the ASsessment in Ankylosing Spondylitis International Working Group criteria (ASAS) for improvement, and markers of inflammation. Results The mean reduction in the total MRI score from week 0 to week 16 was significantly greater in infliximab-treated patients compared with placebo-treated patients (P = 0.033). On average, significantly more lesions resolved in the infliximab group (P < 0.001), while significantly more new lesions developed in the placebo group (P = 0.004). Significantly greater improvement in the infliximab group versus the placebo group was also observed for changes from week 0 to week 16 in the BASDAI (P = 0.002), BASFI (P = 0.004), and ASQoL (P = 0.007) scores. Responses according to the ASAS criteria for 40% improvement, the ASAS criteria for 20% improvement in 5 of 6 domains, and ASAS partial remission were achieved by 61%, 44%, and 56% of infliximab-treated patients, respectively. Infliximab was well tolerated, and no serious adverse events were observed. Conclusion Infliximab was an effective therapy for early sacroiliitis, providing a reduction in disease activity by week 16. This study is the first to show that infliximab is effective for reducing clinical and imaging evidence of disease activity in patients with MRI-determined early axial spondylarthritis.

Ankylosing spondylitis has traditionally been considered a rare disease with no effective therapy. Here, the authors outline why this is no longer the case, and discuss the latest developments in treatment. Copyright © 2006 Wiley Interface Ltd

Objective To determine in vivo the extent of damage to, and changes in turnover of, articular cartilage type II collagen (CII) and the proteoglycan aggrecan following the onset of inflammatory arthritis in humans, and to examine the hypothesis that there are direct relationships between cartilage biomarkers of damage/turnover and clinical, histologic, and molecular markers of inflammation. Methods Synovial fluid (SF) and synovial membrane (SM) were obtained by arthroscopy, and a synovitis score was determined, in 32 patients with rheumatoid arthritis (RA) (13 with early untreated disease, 19 with established disease), 18 with psoriatic arthritis (PsA), and 10 with osteoarthritis (OA). Systemic disease activity markers were recorded, and SM CD3+ T cells, CD4+ T cells, CD68+ macrophages, and lining layer hyperplasia were quantified. SF levels of tumor necrosis factor α (TNFα), interleukin-10 (IL-10), matrix metalloproteinase 1 (MMP-1), MMP-3, Col2-3/4CLong mono neoepitope (C2C) (reflecting collagenase cleavage of cartilage CII), C-propeptide of type II procollagen (PIICP) (a biosynthesis marker), keratan sulfate (KS), and the 846 epitope of aggrecan (turnover) were measured by enzyme-linked immunosorbent assay or radioimmunoassay. Results Levels of cartilage degradation products in early RA or early PsA were not elevated above levels in OA, although in early inflammatory arthritis, TNFα and MMP-1 levels were similar to those observed in late inflammatory disease and higher than those in OA. PIICP was reduced in early RA. Correlations were observed between the SF C2C neoepitope level and the Health Assessment Questionnaire score, C-reactive protein level, plasma viscosity, synovitis score, and SF TNFα and MMP-1 levels. KS epitope content was reduced in direct relation to SM macrophage infiltration in the sublining and lining layers and in the presence of elevated SF MMP-3. Both SF MMP-1 and SF MMP-3 levels correlated with CD4+ T cell infiltration and lining layer hyperplasia in the SM, and MMP-1 levels correlated with lining layer CD68 levels, but TNFα and IL-10 levels did not. Conclusion Except for CII synthesis, there were no significant changes in extracellular matrix turnover of aggrecan or CII in the early stages of human inflammatory arthritis. However, the direct correlation between the increases in TNFα and MMP-1 production and collagen degradation suggests that collagenase cleavage of cartilage collagen is related to the activities of TNFα and MMP-1. The reduction in CII synthesis in early RA may contribute to the developing pathology, since a lack of synthesis of this molecule would inhibit maintenance of cartilage matrix.