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Biomedical subjects

Amnon Sonnenberg

Publications and source records attributed to Amnon Sonnenberg.

At least 19 recordsLinked to original sources
PubMed2006

Causes underlying the birth-cohort phenomenon of peptic ulcer: analysis of mortality data 1911-2000, England and Wales.

BACKGROUND: Since humans have been infected with Helicobacter pylori for millennia, it has remained an enigma why the occurrence of gastric and duodenal ulcer rose suddenly during 19th century. The study aim is to present a mathematical model of H. pylori epidemiology that explains the peculiar long-term trends of ulcer disease. METHODS: Gastric and duodenal ulcer mortality data from England and Wales between 1911 and 2000 were used to validate a model based on two simple and straightforward assumptions about H. pylori infection. First, the infection rate fell in the general population between 1,800 and 2,000. Second, gastric ulcer was caused by H. pylori infection contracted between the ages 5 and 15 and duodenal ulcer was caused by H. pylori infection contracted after the age of 15. As the infection receded in the general population, the two fractions of subjects who became infected between the ages 5 and 15 or after the age of 15 increased among consecutive birth cohorts. RESULTS: The analysis of the actual long-term mortality from gastric and duodenal ulcer indicates an underlying birth-cohort pattern. These birth-cohort patterns of gastric and duodenal ulcer could be simulated by the interaction of two opposing time trends, namely a declining infection rate and a rising fraction of individuals acquiring their infection at increasingly older ages. The superimposition of a declining and a rising trend resulted in a bell-shaped curve of ulcer occurrence affecting consecutive birth-cohorts born between 1830 and 1970. Similar to the real data, the modelled cohort pattern of gastric ulcer preceded that of duodenal ulcer by 20 years. CONCLUSION: The birth-cohort phenomenon of ulcer disease can be explained by a receding H. pylori infection accompanied by a simultaneous shift in its age of acquisition.

Age of Onset↗
PubMed2006

Endoscopic procedures and diagnoses are not influenced by seasonal variations.

BACKGROUND: The occurrences of various GI diseases are thought to be influenced by seasonal variations. The present study was done to test the hypothesis that seasonal variations in endoscopic diagnoses reflect underlying patterns in the performance of endoscopic procedures. METHODS: The Clinical Outcomes Research Initiative (CORI) uses a computerized endoscopic report generator to collect endoscopic data from 73 diverse practice sites throughout the United States. We used the CORI database to analyze the date-specific occurrence of EGD and colonoscopy, as well as the endoscopic diagnoses of gastric ulcer, duodenal ulcer, and colorectal cancer. Time trends are analyzed by autocorrelation and by linear and nonlinear regression. RESULTS: Between January 2000 and December 2003, the number of EGDs and colonoscopies increased 2.5- and 4.1-fold, respectively. The rate of duodenal ulcer fell from 21.2 (15.6-27.5) to 19.0 (15.8-22.8) per 1000 EGDs. The rate of gastric ulcer fell from 42.6 (33.3-50.1) to 33.4 (29.5-38.7) per 1000 EGDs. The rate of colorectal cancer fell from 109.9 (98.3-122.8) to 72.2 (67.4-77.2) per 1000 colonoscopies. The time trends of neither endoscopic procedures nor endoscopic diagnoses revealed any seasonal variation or other cyclic pattern. CONCLUSIONS: The performance of endoscopic procedures is unaffected by any seasonal variation.

Endoscopy, Gastrointestinal↗
PubMed2006

Is endoscopic screening before major surgical procedures warranted?

BACKGROUND: Gastroenterologists are frequently requested to perform endoscopic procedures to rule out cancer or other serious GI disease before major surgical operations. OBJECTIVE: To assess whether such requests are warranted. DESIGN: Cost benefit analysis by using decision tree and threshold analysis. PATIENTS: Subjects scheduled for liver and kidney transplant or other major surgeries. MAIN OUTCOME MEASUREMENTS: Costs of medical and surgical procedures. The threshold value is defined as the a priori probability for a GI diagnosis, where the benefit of endoscopy changes from unfavorable to favorable as the diagnostic probability increases. RESULTS: For all types of organ transplants, the threshold probability for diagnosing a GI disease by endoscopy is lower than 1%. Such a low threshold suggests that if a disease cannot be ruled out with certainty before transplant operations or any other major surgical operation, endoscopic screening would be warranted. For lesser interventions, such as percutaneous transluminal coronary angioplasty and coronary bypass grafting, the threshold value varies between 3.2% and 6.5%, which suggests that endoscopic screening may be justified if there are sufficient grounds to suspect a comorbid medical condition that could compromise the success of the planned surgical intervention. LIMITATIONS: The model only considers procedure costs and assumes no endoscopic complications. CONCLUSIONS: Endoscopic screening before costly and invasive surgical or other medical interventions is justified.

Cost-Benefit Analysis↗
PubMed2006

Vicious circles in inflammatory bowel disease.

BACKGROUND: Inflammatory bowel disease can present with a bewildering array of disease manifestations whose overall impact on patient health is difficult to disentangle. The multitude of disease complications and therapeutic side effects result in conflicting ideas on how to best manage a patient. The aim of the study is to test the usefulness of influence diagrams in resolving conflicts centered on managing complex disease processes. METHODS: The influences of a disease process and the ensuing medical interventions on the health of a patient with inflammatory bowel disease are modeled by an influence diagram. Patient health is the focal point of multiple influences affecting its overall strength. Any downstream influence represents the focal point of other preceding upstream influences. The mathematics underlying the influence diagram is similar to that of a decision tree. Its formalism allows one to consider additive and inhibitory influences and include in the same analysis qualitatively different types of parameters, such as diagnoses, complications, side effects, and therapeutic outcomes. RESULTS: Three exemplary cases are presented to illustrate the potential use of influence diagrams. In all three case scenarios, Crohn's disease resulted in disease manifestations that seemingly interfered with its own therapy. The presence of negative feedback loops rendered the management of each case particularly challenging. The analyses by influence diagrams revealed subtle interactions among the multiple influences and their joint contributions to the patient's overall health that would have been difficult to appreciate by verbal reasoning alone. CONCLUSION: Influence diagrams represent a decision tool that is particularly suited to improve decision-making in inflammatory bowel disease. They highlight key factors of a complex disease process and help to assess their quantitative interactions.

Adult↗
PubMed2005

The inevitable rise of mediocrity in academic medicine.

The present analysis addresses the question of how it has been possible for academic medicine to grow and lose its creative productivity at the same time. A mathematical model is developed to simulate the mechanisms that govern growth of medical systems over time. Time-dependent growth of system size increases the occurrence of statistical deviations of all system parameters. Deviations are correlated with costs and creative output. As deviation-induced costs start to strain the system's tolerance, means become implemented to restrict deviation, which ultimately also reduces its creative output. To maintain growth combined with high levels of creative output, an academic medical system would need to continuously branch off and nurture smaller subsystems, which pursue their own set of goals relatively independently of the overall academic structure.

Academic Medical Centers↗
PubMed2005

Prevalence and socioeconomic impact of upper gastrointestinal disorders in the United States: results of the US Upper Gastrointestinal Study.

BACKGROUND & AIMS: This study examined the prevalence of upper gastrointestinal (GI) symptoms and symptom groupings and determined impact on disability days in a nationally representative US sample. METHODS: A telephone survey of 21,128 adults was conducted including questions about the presence of upper GI symptoms during the past 3 months. Respondents were categorized as symptomatic (ie, reported GI symptoms once per month) or asymptomatic. The survey included questions about missed work, leisure activity, or household activity days. Symptom groupings were identified by using factor analysis, and cluster analysis was used to assign respondents into distinct groups on the basis of these symptom groupings. RESULTS: The prevalence of an average of 1 or more upper GI symptoms during the past 3 months was 44.9%. The most common symptoms experienced during the past 3 months were early satiety, heartburn, and postprandial fullness. Factor analysis identified 4 symptom groupings: (1) heartburn/regurgitation; (2) nausea/vomiting; (3) bloating/abdominal pain; and (4) early satiety/loss of appetite. Five respondent clusters were identified; the largest clusters were primarily early satiety/fullness (44%) and gastroesophageal reflux disease-like symptoms (28%). Two small clusters reflected nausea and vomiting (7%) and a heterogeneous symptom profile (4%). Symptomatic respondents reported significantly more missed work, leisure, and household activity days than asymptomatic respondents (all P < .0001). CONCLUSIONS: Factor analysis separated GI symptoms into groupings reflecting gastroesophageal reflux disease and dyspepsia: early satiety, postprandial fullness, and loss of appetite; bloating and abdominal pain/discomfort; and nausea and vomiting. These upper GI symptoms were associated with significant loss of work and activity days.

Adolescent↗
PubMed2005

Comparing risks and benefits of colorectal cancer screening in elderly patients.

BACKGROUND & AIMS: In patients with limited life expectancy, the risks of colorectal cancer screening may outweigh the benefits. The aim of this study was to quantify risks and benefits of different screening strategies in elderly patients with varying life expectancies. METHODS: We examined risks and benefits of screening in patients aged 70-94 years with differing health status using 3 strategies: annual fecal occult blood tests, flexible sigmoidoscopy every 5 years, or colonoscopy every 10 years. We compared the number needed to screen to prevent one cancer-related death and the number needed to encounter one screening-related complication for different strategies. RESULTS: The potential benefit from screening varied widely with age, life expectancy, and screening modality. One cancer-related death would be prevented by screening 42 healthy men aged 70-74 years with colonoscopy, 178 healthy women aged 70-74 years with fecal occult blood tests, 431 women aged 75-79 years in poor health with colonoscopy, or 945 men aged 80-84 years in average health with fecal occult blood tests. Colonoscopy screening had the greatest benefit but the highest risk of complications. The potential for screening-related complications was greater than estimated benefit in some population subgroups aged 70 years and older. At all ages and life expectancies, the potential reduction in mortality from screening outweighed the risk of colonoscopy-related death. CONCLUSIONS: The potential benefits and risks of screening vary in elderly patients of different life expectancies. For any individual patient, the potential for harm from screening must be weighed against the likelihood of benefit, especially with shorter life expectancy.

Aged↗
PubMed2005

How to predict the future (outcome of gastrointestinal disease).

This short review is aimed to illustrate three simple rules to predict the outcome of a gastrointestinal disease. The first rule relates to the principle of WYSIWYG, that is, "what you see is what you get." To predict the future of a given digestive disease, the gastroenterologist needs to pay close attention to its present appearance and develop clear understanding of its pathophysiology. To delineate future trends, as a second rule, the gastroenterologist needs to delineate past trends and try to extrapolate them into the near future. Third, the length of the past medical history also provides a reliable estimate for the expected future lifetime of a gastrointestinal disease. These rules enable gastroenterologists to enlighten themselves, as well as their patients, about the future outcome of a given gastrointestinal disease.

Confidence Intervals↗
PubMed2005

Lack of seasonal variation in the endoscopic diagnoses of Crohn's disease and ulcerative colitis.

BACKGROUND: Conflicting data have been reported about the seasonal variation of inflammatory bowel diseases (IBD). The purpose of the present analysis was to assess the occurrence of seasonal variations in the endoscopic diagnosis of Crohn's disease (CD) and ulcerative colitis (UC). METHODS: The Clinical Outcomes Research Initiative (CORI) uses a computerized endoscopic report generator to collect endoscopic data from 73 diverse practice sites throughout the United States. We utilized the CORI database to analyze the date-specific occurrence of colonoscopy, as well as the colonoscopic diagnoses of CD and UC. Time trends were analyzed by autocorrelation, linear, and nonlinear regression. RESULTS: Between January 2000 and December 2003, the number of colonoscopies increased 4.1-fold. The proportion of colonoscopies with a CD diagnosis fell by 28%, and the proportion of colonoscopies with a UC diagnosis fell by 50%. The occurrence of neither CD nor UC was shaped by any clear-cut seasonal periodicity. However, the trends of the two diseases revealed strikingly similar patterns with four resembling peaks superimposed on their monthly fluctuations. CONCLUSIONS: Endoscopic diagnosis of IBD is unaffected by any seasonal variation. The decline in the diagnostic rate of colonic IBD may reflect a relative increase in the utilization of colonoscopy for colon cancer screening. The similarity in the monthly fluctuations of both IBD suggests that their incidence or flare-ups may be influenced by identical exogenous risk factors.

Adult↗
PubMed2004

Retransplantation for recurrent hepatitis C in the MELD era: maximizing utility.

1. Retransplantation (re-LT) for hepatitis C virus (HCV) recurrence is controversial. Although re-LT accounts for 10% of all liver transplants (LTs), the number of patients requiring re-LT is expected to grow as primary LT recipients survive long enough to develop graft failure from recurrent disease. 2. Utility, as applied to the medical ethics of transplantation, refers to allocating organs to those individuals who will make the best use of them. The utility function (U) of liver transplantation is represented by the product of outcome (O = 1-year survival with LT) times emergency (E = 3-month mortality without LT), i.e., U = O x E. 3. For primary LT, maximal U is achieved by allocating organs at the highest model for end-stage liver disease (MELD) score (i.e., "sickest first"). No significant differences exist between HCV and non-HCV diagnoses. 4. For re-LT, maximal utility for HCV and non-HCV diagnoses are achieved at MELD scores of 21 and 24, respectively. Utility starts to decline at MELD scores above 28. 5. The current allocation system (MELD) fails to maximize utility with regard to re-LT.

Decision Support Techniques↗
PubMed2004

Process and accomplishment in academic medicine.

Medical academic systems are characterized by interplay between accomplishment and process. The term accomplishment refers to fulfillment of the system's original goals, such as education, research and medical care, whereas the term process refers to the culture and structure, which are developed to pursue these goals. A mathematical model is developed to simulate the mechanisms that govern growth of medical systems over time. Because system performance is easier to measure by process than accomplishment, in the long run investments in growth are shifted away from accomplishment towards process. In all aging medical systems alike, the proportion of process tends to increase at the expense of accomplishment.

Academic Medical Centers↗
PubMed2004

We only see what we already know--a modified Bayes' formula to explain inherent limitations of diagnostic tests.

In medical tests involving human judgment, human testers are inclined to diagnose only symptoms and signs that they already know. The present analysis delineates the relationship between prior knowledge and test characteristics. The relationship between test outcome and a given diagnosis is generally described in terms of sensitivity and specificity. In the present analysis, this relationship is broken down into two separate contributions: First, the association between the test measure and the presence of disease and second, the association between the actual test outcome and the presence of the test measure. The second relationship describes the performance of a human tester in assessing the presence of a test measure irrespective of the disease status. Bayes' formula can be adjusted to include contributions by both relationships. The ability to increase a diagnostic probability through testing depends on a tester's familiarity with the test measure and reliability in eliciting its presence. Testing yields the most reliable results if the test measure falls well within a tester's own level of competence. Test measures outside the tester's competence level lead to tests with worse outcome than no testing at all.

Animals↗
PubMed2004

Exploring how to tell the truth and preserve hope: can a balance between communication and empathy be calculated?

BACKGROUND & AIMS: When told the harsh truth about severe disease, a patient might despair and lose all hope. Without knowing the truth, however, the patient cannot participate in decision making and adjust life according to his illness. The present study aims to analyze the relationships between hope and truth in the decision on how much information to disclose to a patient with severe gastrointestinal disease. METHODS: The decision analysis is based on the economic concepts of indifference curves and utility function. An inverse linear relationship exists between hope and truth; as more truth becomes revealed, the amount of hope declines. The utility function and the corresponding indifference curve of hope plotted versus truth describe the patient's personal choices among different combinations of hope and truth. The optimal choice among various combinations of hope and truth corresponds with the point at which the inverse hope-truth line meets the indifference curve. RESULTS: In situations in which hope drops steeply as more medical facts are being revealed, the utility to the patient is maximized with less truth being told. With a less pronounced truth-related decline in hope, utility is maximized at higher levels of truth, and, occasionally, utility is maximized only after all medical facts have been disclosed. The lesser the impact of truth on hope, the more truth is being tolerated. CONCLUSIONS: A caring gastroenterologist trying to optimize his/her patient's well-being should try to assess the potential influence of truth on the patient's psyche and dispense it accordingly.

Adaptation, Psychological↗
PubMed2004

A critical review of the diagnosis and management of Barrett's esophagus: the AGA Chicago Workshop.

BACKGROUND & AIMS: The diagnosis and management of Barrett's esophagus (BE) are controversial. We conducted a critical review of the literature in BE to provide guidance on clinically relevant issues. METHODS: A multidisciplinary group of 18 participants evaluated the strength and the grade of evidence for 42 statements pertaining to the diagnosis, screening, surveillance, and treatment of BE. Each member anonymously voted to accept or reject statements based on the strength of evidence and his own expert opinion. RESULTS: There was strong consensus on most statements for acceptance or rejection. Members rejected statements that screening for BE has been shown to improve mortality from adenocarcinoma or to be cost-effective. Contrary to published clinical guidelines, they did not feel that screening should be recommended for adults over age 50, regardless of age or duration of heartburn. Members were divided on whether surveillance prolongs survival, although the majority agreed that it detects curable neoplasia and can be cost-effective in selected patients. The majority did not feel that acid-reduction therapy reduces the risk of esophageal adenocarcinoma but did agree that nonsteroidal antiinflammatory drugs are associated with a cancer risk reduction and are of promising (but unproven) value. Participants rejected the notion that mucosal ablation with acid suppression prevents adenocarcinoma in BE but agreed that this may be an appropriate strategy in a subgroup of patients with high-grade dysplasia. CONCLUSIONS: Based on this review of BE, the opinions of workshop members on issues pertaining to screening and surveillance are at variance with published clinical guidelines.

Adenocarcinoma↗
PubMed2004

Endoscopic evaluation of patients with dyspepsia: results from the national endoscopic data repository.

BACKGROUND & AIMS: Endoscopy is commonly performed to evaluate symptoms of dyspepsia. The aim of this study was to characterize patients who receive endoscopy for dyspepsia and measure predictors of primary endoscopic outcomes, utilizing a large national endoscopic database. METHODS: The Clinical Outcomes Research Initiative (CORI) receives endoscopy reports from a network of 74 sites in the United States. Sixty-one percent of reports come from private practice settings. Patients with reflux dyspepsia and nonreflux dyspepsia were identified from January 2000 to June 2002. Patients with dysphagia and known Barrett's esophagus were excluded. Primary endoscopic outcomes included esophageal inflammation and stricture, gastric ulcer, duodenal ulcer, suspected Barrett's esophagus (> or =2 cm), and suspected esophageal and gastric malignancy. The presence or absence of alarm symptoms (vomiting, weight loss, and evidence of GI blood loss) was determined. Adjusted relative risk (RR) for predicting serious outcomes was calculated in a multivariate model. RESULTS: We received 117,497 endoscopic reports, representing 99,558 unique patients. Dyspepsia, with and without reflux symptoms, accounted for 43% of upper endoscopies. Among dyspeptic patients, 36.5% were younger than 50 years of age without alarm symptoms. Esophageal or gastric malignancy in patients with dyspepsia was associated with increasing age, male sex, Asian race, Native American race, and symptoms of weight loss and vomiting. Suspected Barrett's esophagus (> or =2 cm) was associated with reflux symptoms, male sex, age, and white race. Ulcers were associated with evidence of bleeding, vomiting, male sex, black race, and Hispanic ethnicity. CONCLUSIONS: These practice-based data reveal important practice behaviors and outcomes.

Adult↗
PubMed2004

Decision analysis in clinical gastroenterology.

OBJECTIVES: Although the tools of medical decision analysis have been mostly used to address complex issues of healthcare and management policies, an important role remains for decision analysis to play in solving mundane medical problems of daily practice. The present article aims to restate the origins of decision analysis and to demonstrate the utility of decision models in clinical gastroenterology. METHODS: Three clinical scenarios are presented to illustrate the applicability of decision analysis in clinical gastroenterology. The examples are modeled as simple decision trees and phrased in terms of threshold analysis. RESULTS: In spite of its striking simplicity, the framework of threshold analysis is able to capture a large variety of heterogeneous and often perplexing medical problems. Rather than calculate a cost-effectiveness or cost-benefit ratio, the result of the analysis is expressed as a probability value, which forms the threshold between the two choices against or in favor of a particular medical action. For most analyses little if any calculation is needed to solve the decision tree, and the final outcome of the analysis can be derived based on comparative estimates and considerations of magnitude only. CONCLUSIONS: The study demonstrates that threshold analysis can serve as a simple and convenient instrument to solve a large variety of problems in clinical gastroenterology.

Decision Support Techniques↗