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Biomedical subjects

James D Lewis

Publications and source records attributed to James D Lewis.

At least 37 records · Page 2Linked to original sources
PubMed2005

Site organization and management.

The principal investigator is responsible for everything involved in the conduct of a clinical research study. Prior to the initiation of any clinical trial, an investigator must become acquainted with the material requirements, personnel needs, and best practices involved in the conduct of the trial. Commitment to a clinical trial should not be taken lightly because even a simple study may require a major investment of staff, space, and time. Standard operating procedures help to standardize staff training and improve regulatory compliance. Reasons for participation in clinical research may differ between community and academic gastroenterologists, but responsibility for patient care, regulatory requirements, and assumption of accountability are identical. Careful attention to the details of site organization, administrative requirements, and patient recruitment and retention all contribute to the successful performance of clinical research.

Biomedical Research↗
PubMed2005

Design issues and outcomes in IBD clinical trials.

Successful clinical trials in inflammatory bowel disease are based on precise definitions of study populations, standardized and well-defined interventions, reliable indices of disease activity, and clearly stipulated outcome measures. Interpretation of research results is often complicated by the differentiation of goals of therapy (remission induction and maintenance, quality of life) and the multitude of patient subsets. Choosing the correct patient subtype to enroll in a clinical trial is critical to the results of a study, its conclusions, and its applicability to the clinical setting. Validated, easy-to-use disease activity indices allow interpretation of results across trials. The use of biomarkers as surrogate clinical endpoints provides reproducibility, ease of statistical handling as a continuous variable, and consistent measurement of response to treatment. Despite these potential advantages, biomarkers of disease activity lack specificity and will need to be validated against clinically meaningful outcomes. Careful subject selection, standardization of disease activity indices, and precise outcome measurement are the keys to continued improvement of the inflammatory bowel disease research process.

Biomarkers↗
PubMed2005

State of the art: IBD therapy and clinical trials in IBD.

Inflammatory bowel diseases (IBD) encompass Crohn's disease and ulcerative colitis, which are diseases characterized by chronic intestinal inflammation. IBD is believed to result from predisposing genetic and environmental factors (specific antigens and pathogen-associated molecular patterns) acting on the immunoregulatory system and causing inflammation of the gastrointestinal mucosa. IBD may be the result of an imbalance of effector (proinflammatory) and regulatory T-cell responses. Three scenarios indicative of the outcome of this balance exist in animal models: balanced effector and regulatory T cells resulting in a normal controlled inflammation; overactive effector T cells resulting in inflammation and disease; and an absence of regulatory T cells resulting in uncontrolled inflammation and severe, aggressive disease. The number of products under study for the treatment of IBD has increased from 3 products and 1 target in 1993 to more than 30 products and more than 10 targets in 2005. The number of products under development and continued investigations into the pathogenesis of IBD emphasize the need to expand clinical research efforts in IBD.

Animals↗
PubMed2005

Atmospheric CO2 enrichment alters energy assimilation, investment and allocation in Xanthium strumarium.

Energy-use efficiency and energy assimilation, investment and allocation patterns are likely to influence plant growth responses to increasing atmospheric CO2 concentration ([CO2]). Here, we describe the influence of elevated [CO2] on energetic properties as a mechanism of growth responses in Xanthium strumarium. Individuals of X. strumarium were grown at ambient or elevated [CO2] and harvested. Total biomass and energetic construction costs (CC) of leaves, stems, roots and fruits and percentage of total biomass and energy allocated to these components were determined. Photosynthetic energy-use efficiency (PEUE) was calculated as the ratio of total energy gained via photosynthetic activity (Atotal) to leaf CC. Elevated [CO2] increased leaf Atotal, but decreased CC per unit mass of leaves and roots. Consequently, X. strumarium individuals produced more leaf and root biomass at elevated [CO2] without increasing total energy investment in these structures (CCtotal). Whole-plant biomass was associated positively with PEUE. Whole-plant construction required 16.1% less energy than modeled whole-plant energy investment had CC not responded to increased [CO2]. As a physiological mechanism affecting growth, altered energetic properties could positively influence productivity of X. strumarium, and potentially other species, at elevated [CO2].

Atmosphere↗
PubMed2005

Women with a prior diagnosis of breast cancer are not at an increased risk for subsequent colorectal cancer.

BACKGROUND: Earlier studies regarding the risk of colorectal cancer in women with a prior diagnosis of breast cancer yielded conflicting results. METHODS: A retrospective cohort study was performed using the General Practitioner Research Database of the United Kingdom. Women with a prior diagnosis of breast cancer were compared with female control patients without a prior history of breast cancer. The primary outcome was an incident diagnosis of colorectal cancer. Poisson regression analysis was utilized to assess the effects of potential confounder variables. RESULTS: The study included 17,415 breast cancer patients and 69,660 matched control patients with follow-up time in person years of 52,914 and 331,480, respectively. The relative rate of colorectal cancer among breast cancer patients was 0.80 (95% CI 0.56-1.15). The relative rate of colorectal cancer among women exposed and unexposed to tamoxifen were 0.73 (95% CI 0.49-1.08) and 1.81 (95% CI 0.85-3.85), respectively. CONCLUSION: Women with a prior diagnosis of breast cancer are not at an increased risk of colorectal cancer; these women can follow average risk screening guidelines for colorectal cancer.

Adult↗
PubMed2005

Selective serotonin re-uptake inhibitors and the risk of bleeding.

Despite their safety, selective serotonin re-uptake inhibitors (SSRIs) are associated with bleeding. The authors critically reviewed the medical literature on SSRIs to identify subgroups of patients at risk of bleeding complications. The authors performed a literature search using MEDLINE from 1966 to 1st September 2004 using; 'haemorrhage, serotonin uptake inhibitors and antidepressive agents' as search terms and followed up on citations in each paper that was relevant to SSRI associated bleeding. The authors reviewed 7 retrospective analytical studies and 24 case reports of bleeding in 43 different people. Analytical studies support an association between SSRI consumption and upper gastrointestinal (GI) bleeding and perioperative bleeding. Little evidence links SSRI use with intracerebral haemorrhage. The risk of GI bleeding appeared to be highest among patients consuming SSRIs with NSAIDs. Combining aspirin or NSAIDs with SSRIs may further increase the risk of bleeding. Clinicians should caution patients about combining SSRIs with aspirin or NSAIDs. Pharmacotherapy to reduce the risk of GI bleeding should be considered in high risk patients.

Adult↗
PubMed2004

Influence of alcohol use, race, and viral coinfections on spontaneous HCV clearance in a US veteran population.

Hepatitis C virus (HCV) is spontaneously cleared in 15% to 45% of individuals during primary infection. To define the role of alcohol, race, and HBV or HIV coinfections in natural HCV clearance, we examined these parameters in 203 spontaneously HCV-recovered subjects (HCV Ab(+)/RNA(-) subjects without prior antiviral therapy) and 293 chronically HCV-infected patients (HCV Ab(+)/RNA(+)). Subjects were identified from 1,454 HCV antibody-seropositive US veterans tested for HCV RNA between January 2000 and July 2002 at the Philadelphia Veterans Affairs Medical Center. In univariate analysis, alcohol use disorder (odds ratio [OR] 0.52; 95% CI, 0.31-0.85; P =.006) and black race (OR 0.65; 95% CI, 0.44-0.96; P =.024) were both associated with decreased likelihood of spontaneous HCV clearance. In multivariate analyses adjusting for race, HIV infection, age, and alcohol use disorder, alcohol remained strongly associated with reduced HCV clearance (OR 0.49; 95% CI, 0.30-0.81; P =.005). In contrast, the association between black race and viral clearance was no longer statistically significant (adjusted OR 0.72; 95% CI, 0.48-1.09; P =.125). HIV coinfection was negatively associated with HCV clearance (OR 0.37; 95% CI, 0.16-0.83; P =.016), while HBV coinfection was positively associated with HCV clearance (unadjusted OR 5.0; 95% CI, 1.26-28.6; P =.008). In conclusion, the likelihood of spontaneous clearance of HCV may be influenced by alcohol and viral coinfections.

Alcohol Drinking↗
PubMed2004

Agreement between GPRD smoking data: a survey of general practitioners and a population-based survey.

BACKGROUND: Cigarette smoking is a common habit that is associated with many diseases. Smoking is often an important confounding variable in pharmacoepidemiological studies. The General Practice Research Database (GPRD) is widely used in pharmacoepidemiological research. In this study, we compare data recorded in the GPRD with the smoking history obtained from direct query of general practitioners (GPs) and from a population-based survey. METHODS: We completed a mailed survey of GPs caring for a random sample of 150 patients with inflammatory bowel disease. The survey asked the GP to categorize the patients smoking status on a specified date. These results were then compared to the data recorded in the GPRD. Smoking status of 225,308 randomly selected GPRD patients without inflammatory bowel disease was compared to the results of a population-based household survey. RESULTS: Completed surveys with usable data were received from GPs on 136 of the 150 patients (91%). The sensitivity and positive predictive value of the database for current smoking were 78% (95% CI: 52-94) and 70% (95% CI: 46-88) respectively. The sensitivity and positive predictive value of former smoking were 53% (95% CI: 28-77) and 60% (95% CI: 32-84) respectively. Current and former smoking rates in the GPRD were 79% and 29% respectively of expected rates according to the population-based survey. CONCLUSIONS: Current smoking is more completely recorded in the GPRD than former smoking. These data need to be considered when planning GPRD studies where smoking is an important exposure variable.

Adolescent↗
PubMed2004

Schatzki ring and Barrett's esophagus: do they occur together?

Our purpose was to determine the prevalence of Barrett's esophagus in the presence of Schatzki ring. We performed a retrospective case-control study with an endoscopic database. Barrett's esophagus was present in 3 of 409 (0.73%) patients with Schatzki ring and in 16 of 888 (1.80%) patients without Schatzki ring. Short segment Barrett's esophagus was present in 3 cases and 10 controls. Long segment Barrett's esophagus was present in no cases and six controls. Logistic regression models adjusting for the presence of a hiatal hernia revealed a significant decrease in the odds of Barrett's esophagus in cases compared to controls (OR, 0.24; 95% CI, 0.07-0.87; P = 0.029). Barrett's esophagus is less prevalent in patients with Schatzki ring compared to patients without Schatzki ring. Long segment Barrett's esophagus was not observed in patients with Schatzki ring. A responsible protective effect or mutually exclusive pathophysiology should be considered.

Barrett Esophagus↗
PubMed2004

Seasonal variation in flares of inflammatory bowel disease.

BACKGROUND & AIMS: Previous research has yielded conflicting data as to whether the natural history of inflammatory bowel disease follows a seasonal pattern. The purpose of this study was to determine whether relapse of inflammatory bowel disease follows a seasonal pattern either across a cohort of patients or within individual patients. METHODS: We used 1988 to 1997 data from the General Practice Research Database to conduct a retrospective cohort study of 1587 patients with Crohn's disease (mean age at start of follow-up, 41 +/- 17 years) and 2773 patients with ulcerative colitis (mean age at start of follow-up, 48 +/- 16 years). Flares of disease were identified by receipt of a new prescription for either corticosteroids or 5-ASA medications following an interval of at least 4 months without prescriptions for either class of medication. Logistic regression was used to adjust the association of season of the year and flare of disease for potential confounding variables. RESULTS: There was no association between season of the year and flare of Crohn's disease (P = 0.66). Season of the year was only weakly associated with flares of ulcerative colitis (P = 0.02). Compared with winter, spring had very slightly higher rates of flares (OR = 1.13, 95% CI: 1.05-1.23). We did not observe seasonal patterns within individual patients experiencing multiple flares (P > 0.05 for Crohn's disease and ulcerative colitis). CONCLUSIONS: Although we observed a slight increase in exacerbations of ulcerative colitis in the spring, in general, these data do not support an association between season of the year and flares.

Adrenal Cortex Hormones↗
PubMed2004

A meta-analysis of the placebo rates of remission and response in clinical trials of active Crohn's disease.

BACKGROUND & AIMS: Placebo-controlled, randomized clinical trials (PC-RCTs) are commonly used to assess therapies for Crohn's disease (CD). Knowledge of the placebo rates of remission and response and understanding of design factors that influence these rates is important for designing future clinical trials evaluating pharmacotherapy of CD. The aims of this study were to estimate rates of remission and response in patients with active CD receiving placebo and to identify factors influencing these rates. METHODS: We performed a systematic review and meta-analysis of PC-RCTs evaluating therapies for active CD identified from MEDLINE from 1966 to 2001. RESULTS: The pooled estimates of the placebo rates of remission and response were 18% (95% confidence interval, 14%-24%; range, 0%-50%) and 19% (95% confidence interval, 13%-28%; range, 0%-46%), respectively, both with significant heterogeneity among studies (P < 0.01 for remission, P < 0.03 for response). In multivariate models, study duration, number of study visits, and entry Crohn's Disease Activity Index score were important predictors of the placebo remission rate, with study duration the most important. However, no single factor could account for all of the heterogeneity. Factors that influence the placebo response rates were similar to those affecting the placebo remission rates. The absolute benefit of active treatment beyond placebo was generally larger when outcome was measured by response than remission. CONCLUSIONS: Placebo remission and response rates in PC-RCTs for active CD are variable. Study duration, number of study visits, and disease severity at entry have a large influence on placebo remission rates.

Controlled Clinical Trials as Topic↗
PubMed2004

Insulin therapy and colorectal cancer risk among type 2 diabetes mellitus patients.

BACKGROUND & AIMS: Endogenous hyperinsulinemia in the context of type 2 diabetes mellitus is potentially associated with an increased risk of colorectal cancer. We aimed to determine whether insulin therapy might increase the risk of colorectal cancer among type 2 diabetes mellitus patients. METHODS: We conducted a retrospective cohort study among all patients with a diagnosis of type 2 diabetes mellitus in the General Practice Research Database from the United Kingdom. We excluded patients with <3 years of colorectal cancer-free database follow-up after the diabetes diagnosis as well as those insulin users who developed colorectal cancer after <1 year of insulin therapy. The remaining insulin users and the noninsulin-using type 2 diabetic patients were followed for the occurrence of colorectal cancer. Hazard ratios (HR) were determined in Cox proportional hazard analysis. A nested case-control study was conducted to perform multivariable analysis and to determine a duration-response effect. RESULTS: The incidence of colorectal cancer in insulin users (n = 3160) was 197 per 100,000 person-years, compared with 124 per 100,000 person-years in type 2 diabetes mellitus patients not receiving insulin (n = 21,758). The age- and sex-adjusted HR of colorectal cancer associated with > or =1 year of insulin use was 2.1 (95% CI: 1.2-3.4, P = 0.005). The positive association strengthened after adjusting for potential confounders. The multivariable odds ratio associated with each incremental year of insulin therapy was 1.21 (95% CI: 1.03-1.42, P = 0.02). CONCLUSIONS: Chronic insulin therapy significantly increases the risk of colorectal cancer among type 2 diabetes mellitus patients.

Aged↗
PubMed2004

Patterns of complementary and alternative medicine use in a population of pediatric patients with inflammatory bowel disease.

Complementary and alternative medicine use is prominent in the United States. The use of complementary and alternative therapies appears to be common in patients with inflammatory bowel disease, but few studies have been completed in children. We sought to examine the extent that children with inflammatory bowel disease in the Greater Philadelphia area (Philadelphia County and the surrounding counties in Delaware, New Jersey, and Pennsylvania) use alternative therapies. We paid particular attention to the specific types of therapies used and whether certain demographic and disease associated factors influence the degree of usage. In this study, we questioned the families of all children diagnosed with inflammatory bowel disease, aged 6 to 16 years and living within Philadelphia and its surrounding counties, who were followed at 1 of the 2 academic pediatric gastroenterology programs that served the area. More than 80% of surveys were returned. Fifty-one percent (95% C.I. 45% to 56%) of patients surveyed reported some form of alternative medicine use within the previous year. Univariate analysis revealed increased use among patients who had Crohn disease, who used the Internet for research on their disease, who reported poor quality of life and had increased school absences in the past year. Therapies associated with alternative medicine use included biological and immunomodulatory therapy. Regression analysis revealed positive associations between use of alternative therapies and expenditure on nonprescription treatments, poor quality of life, Internet research, and the need for calorie supplementation, whereas there was a negative association with history of prior surgery for inflammatory bowel disease.

Adolescent↗
PubMed2003

Age at flowering differentially affects vegetative and reproductive responses of a determinate annual plant to elevated carbon dioxide.

Plant population and community dynamics may be altered by increasing atmospheric CO(2) concentrations [[CO(2)]] through intraspecific variation in the responses of vegetative and reproductive growth. Although these responses may be regulated by age at flowering, little is known about the direct effects of age at flowering on growth responses to elevated [CO(2)]. In this study, we examined the interactive effects of elevated [CO(2)] and age at flowering on absolute and relative allocation to vegetative and reproductive growth in the determinate, short-day species Xanthium strumarium L. (common cocklebur). Six cohorts were planted at 5-day intervals in chambers maintained at either 365 or 730 micro mol mol(-1) CO(2), with an 18-h photoperiod and a non-limiting nutrient supply. All plants were simultaneously induced to flower by switching the photoperiod to 12 h for 2 days, then switching back to an 18-h photoperiod for the remainder of the experiment. All plants were harvested 15 days after the onset of flowering. Total plant biomass increased 11-41% with increasing [CO(2)] and 45% from the youngest to the oldest cohort. Vegetative growth responses to elevated [CO(2)] significantly increased with increasing age at flowering, associated with increasing sink relative to source capacity. In contrast, total fruit mass decreased 32% from the youngest to the oldest cohort and was not significantly affected by CO(2) supply. Relative biomass allocation to fruit decreased 47% from the youngest to the oldest cohort, reflecting decreased numbers of fruit, and 6-28% with increasing [CO(2)], reflecting decreased mean mass per mature fruit. Our findings suggest that elevated [CO(2)] may increase vegetative growth in Xanthium without increasing reproductive biomass, and that age at flowering may influence these responses through effects on source:sink balance. Further, changes in the allometric relationship between vegetative and reproductive growth associated with growth in elevated [CO(2)] suggest that long-term population and community-level responses to elevated [CO(2)] may differ substantially from predictions based on vegetative responses.

Carbon Dioxide↗
PubMed2003

Detection of proximal adenomatous polyps with screening sigmoidoscopy: a systematic review and meta-analysis of screening colonoscopy.

BACKGROUND: The relative effectiveness of flexible sigmoidoscopy compared with colonoscopy to screen for colorectal cancer depends on the magnitude of the association between findings in the proximal and distal colon and the false-negative rate of screening sigmoidoscopy for proximal neoplasia. To address this, we performed a systematic review and meta-analysis of screening colonoscopy studies. METHODS: Published studies through July 31, 2000, of asymptomatic patients undergoing screening colonoscopy were identified from the MEDLINE database. We generated pooled estimates of the odds ratio for the association between findings in the distal and proximal colon and the prevalence of isolated proximal adenomatous neoplasia. RESULTS: Using the sigmoid-descending colon junction to identify the beginning of the distal colon, the pooled odds ratio for the association between distal adenomatous polyps and any proximal neoplasia was 2.40 (95% confidence interval [CI], 1.42-4.05). Diminutive distal adenomatous polyps were also associated with proximal neoplasia (odds ratio, 2.36; 95% CI, 1.30-4.29). Distal hyperplastic polyps were not associated with proximal neoplasia (odds ratio, 1.44; 95% CI, 0.79-2.62). The prevalence of isolated advanced proximal neoplasia in the 3 studies was 2%, 3%, and 5%. Using the sigmoid-descending colon junction to identify the beginning of the distal colon yields a pooled estimate of isolated proximal neoplasia of 16.3% (95% CI, 13.6%-19.1%). CONCLUSIONS: Distal adenomatous polyps, including diminutive distal adenomatous polyps, are associated with an increased prevalence of synchronous proximal neoplasia. Two percent to 5% of patients undergoing screening colonoscopy may have isolated advanced proximal neoplasia. Even more patients may have isolated nonadvanced proximal neoplasia.

Adenomatous Polyps↗