alpha3beta1 and alpha6beta4 integrin receptors for laminin-5 are not essential for epidermal morphogenesis and homeostasis during skin development

Continuous regeneration and homeostasis of the stratified epidermis requires coordinated regulation of cell proliferation, cell differentiation, and cell survival. Integrin-mediated cell adhesion to the extracellular matrix has important roles in regulating each of these processes. Integrins alpha3beta1 and alpha6beta4 are both receptors on epidermal keratinocytes for the basement membrane protein laminin-5, the major ligand for epidermal adhesion in mature skin. Ablation in mice of either alpha3beta1 or alpha6beta4, through null mutation of the gene encoding the alpha3, alpha6, or beta4 integrin subunit, results in epidermal blistering of varying severity. Our previous studies showed that, despite blistering, differentiation and stratification of the epidermis appeared essentially normal in mice that lacked either alpha3beta1 or alpha6beta4. However, these studies did not definitively address the specific developmental importance of each integrin, since they may have overlapping and/or compensatory functions. Given the individual importance of alpha3beta1 or alpha6beta4 in maintaining the dermo-epidermal junction in mature skin, we sought to determine the importance of these integrins for embryonic skin development and epidermal morphogenesis. In the current study, we analyzed skin development in mutant embryos that completely lack both integrins alpha3beta1 and alpha6beta4. Although alpha3beta1/alpha6beta4-deficient embryos displayed epidermal blistering by stage E15.5 of development, they also retained regions of extensive epidermal adhesion to the basement membrane through stage E16.5, indicating alternative adhesion mechanisms. Apoptosis was induced in detached epidermis of alpha3beta1/alpha6beta4-deficient embryos, exemplifying vividly the importance of epithelial attachment to the basement membrane for cell survival. However, apoptotic cells were completely absent from attached epidermis of alpha3beta1/alpha6beta4-deficient embryos, showing that epithelial adhesion that occurred independently of alpha3beta1 and alpha6beta4 also protected cells from apoptosis. Remarkably, in the absence of the known laminin-5 binding integrins (alpha3beta1, alpha6beta4, and alpha6beta1), keratinocytes retained the capacity to proliferate in the epidermis, and epidermal stratification and skin morphogenesis appeared normal prior to blister formation. These findings show that while alpha3beta1 and alpha6beta4 are both required for integrity of the dermo-epidermal junction, neither one is essential for epidermal morphogenesis during skin development.

Screening for high-grade dysplasia in gastroesophageal reflux disease: is it cost-effective?

OBJECTIVE

The present study aimed to assess the cost-effectiveness of endoscopic screening in patients with gastroesophageal reflux disease (GERD) to rule out high-grade dysplasia of Barrett's esophagus.

METHODS

Using an incremental cost-effectiveness ratio as outcome measure, the cost-effectiveness of endoscopic screening was compared to not screening in a decision tree. It was assumed that GERD patients at age 60 yr undergo a one-time endoscopy with esophageal biopsies, targeting abnormal-appearing epithelium. Positive biopsies with respect to high-grade dysplasia or early esophageal adenocarcinoma result in esophagectomy. Transition rates were estimated from U.S. cancer statistics, as well as published data of endoscopic sensitivity, specificity, and surgical outcome. Costs of screening and cancer care were estimated from Medicare reimbursement data from the perspective of a third-party-payor.

RESULTS

Compared with no screening, screening endoscopy cost $24,700 per life-year saved. The cost-effectiveness of screening is quite sensitive to the prevalence of Barrett's esophagus, high-grade dysplasia, and adenocarcinoma, as well as the sensitivity, specificity, and cost of screening endoscopy. A small drop in the health-related quality of life associated with postsurgical states markedly reduced the effectiveness of screening. Simultaneous variations of the prevalence, specificity, and health-related quality of life can easily change screening endoscopy from a life-saving into a life-losing strategy.

CONCLUSIONS

Under favorable conditions, general screening by endoscopy of all patients with reflux symptoms to prevent death from esophageal adenocarcinoma may represent a cost-effective strategy; however, such conditions may be difficult to meet.

Timing and scheduling of endoscopic procedures

BACKGROUND

The aim of the present analysis is to compare the costs associated with different schemes of scheduling tests and to develop recommendations concerning the most cost-effective means for timing individual endoscopic procedures.

METHODS

The diagnostic costs of three competing strategies to schedule various radiologic and endoscopic procedures in patients with jaundice or gastrointestinal hemorrhage are compared by computer models using a Monte Carlo simulation. In strategy 1, the evaluation is started with the most promising procedure and proceeds with the next most promising procedure in case of a normal finding. In strategy 2, physicians adhere to a rigid sequence of diagnostic tests that starts with the least expensive procedure and advances through progressively more expensive procedures. In strategy 3, all promising tests are scheduled at the onset without waiting for test results to decide in favor or against individual procedures. In the Monte Carlo simulation, two hypothetical populations of 5000 inpatients or outpatients are subjected to each strategy.

RESULTS

Unless one particular diagnosis is suspected with a high a priori probability, a rigid sequence of advancing from less to more expensive and invasive procedures provides the cheapest diagnostic strategy. In case of limited access to endoscopy and long waiting times, the cheapest work-up may include simultaneous scheduling of complementary procedures without waiting for intermediate test results. Strategy 1 of starting with the most promising test procedure becomes the least expensive option, if the prior probability assigned to the most likely diagnosis exceeds a threshold between 40% and 70%, depending on the type of test needed to make the diagnosis.

CONCLUSIONS

An expeditious diagnostic evaluation or an evaluation that is guided primarily by medical considerations is more likely to result in low healthcare costs.

The impact of colorectal cancer screening on life expectancy

METHODS

The purpose of this study was to assess the effect of screening for colorectal cancer on life expectancy and estimate the number of colonoscopies needed per life year saved. The declining exponential approximation of life expectancy was used to calculate the effect of colorectal cancer screening on expected remaining lifetime. The annual number of deaths from colorectal cancer and the size of the population were obtained from the vital statistics of the United States. Published reports were consulted to determine the decrease in mortality from colorectal cancer achieved by fecal occult blood testing, screening sigmoidoscopy or colonoscopy. A Markov chain analysis was used to determine the endoscopic resources required to screen and survey the entire population of U.S. residents age 50 years until death or age 85 years.

RESULTS

Colorectal cancer decreases the life expectancy of U.S. residents aged 50 to 54 years by 292 days and those aged 70 to 74 years by 70 days. Screening with fecal occult blood tests extends expected lifetime of the 2 age groups by 51 and 12 days, respectively, whereas screening with sigmoidoscopy leads to increases of 86 and 21 days. Colonoscopic screening increases expected lifetime by 170 and 41 days, respectively. The number of colonoscopies needed to save 1 year of expected life ranges from 2.9 to 6.0, depending on the type of screening regimen used.

CONCLUSIONS

The extension of life through screening colonoscopy is two or three times longer than the extension achieved through flexible sigmoidoscopy or fecal occult blood test, respectively. Although a large number of colonoscopies are required to screen the U.S. population, relatively few colonoscopies need to be invested per year of life expectancy saved.

Cost effectiveness of competing strategies to prevent or treat GORD-related dysphagia

OBJECTIVES

The variety of influences that contribute to the occurrence of dysphagia in gastro-oesophageal reflux disease (GORD) provide the physician with many options to intervene in the pathophysiology of the disease process. The aims of the present analysis were to compare the relationships between the costs and effectiveness of competing therapeutic interventions in preventing dysphagia.

METHODS

Dysphagia was modelled as the focal point of multiple influences leading to its development. The costs associated with different forms of drug therapy were based on the average wholesale prices listed in the Red Book of 1998. Procedural costs were estimated from Medicare reimbursements. Different treatment options were assessed by their incremental cost-effectiveness ratio.

RESULTS

Lifestyle modifications, treatment with prokinetic agents or antacids reduce the occurrence of dysphagia by 22, 21 or 25%, respectively. Acid inhibition results in a 57 to 89% reduction of dysphagia, depending on treatment with histamine-2-receptor antagonists (H2RAs) or proton pump inhibitors (PPIs). Oesophageal dilation results in a reduction ranging between 54 and 81%. The incremental ratio of cost effectiveness associated with prokinetic agents or H2RAs is much higher than that of PPIs. Based on the concept of extended dominance, therefore, prokinetic drugs and H2RAs do not constitute cost-effective means to prevent dysphagia and should be excluded in favour of treatment with PPIs.

CONCLUSIONS

An economic analysis of various treatment strategies to reduce the risk of GORD-related dysphagia indicates that PPIs are the most cost-effective means to prevent its occurrence.

A decision analysis of surveillance for colorectal cancer in ulcerative colitis

BACKGROUND

Patients with long standing, extensive ulcerative colitis have an increased risk of developing colorectal cancer.

AIMS

To assess the feasibility of surveillance colonoscopy in preventing death from colorectal cancer.

PATIENTS

A hypothetical cohort of patients with chronic ulcerative colitis.

METHODS

The benefits of life years saved were weighted against the costs of biannual colonoscopy and proctocolectomy, and the terminal care of patients dying from colorectal cancer. Two separate Markov processes were modelled to compare the cost-benefit relation in patients with or without surveillance. The cumulative probability of developing colorectal cancer served as a threshold to determine which of the two management strategies is associated with a larger net benefit.

RESULTS

If the cumulative probability of colorectal cancer exceeds a threshold value of 27%, surveillance becomes more beneficial than no surveillance. The threshold is only slightly smaller than the actual cumulative cancer rate of 30%. Variations of the assumptions built into the model can raise the threshold above or lower it far below the actual rate. If several of the assumptions are varied jointly, even small changes can lead to extreme threshold values.

CONCLUSIONS

It is not possible to prove that frequent colonoscopies scheduled at regular intervals are an effective means to manage the increased risk of colorectal cancer associated with ulcerative colitis.

Formation of hemidesmosome-like structures in the absence of ligand binding by the (alpha)6(beta)4 integrin requires binding of HD1/plectin to the cytoplasmic domain of the (beta)4 integrin subunit

Hemidesmosomes are adhesion structures that mediate anchorage of epithelial cells to the underlying basement membrane. We have previously shown that the (alpha)6(beta)4 integrin can induce the assembly of these multi-protein structures independent of binding to its ligand laminin-5 (ligand-independent formation of hemidesmosomes). Our results suggested a role for HD1/plectin, which binds to the cytoplasmic domain of the (beta)4 integrin subunit, in controlling the clustering of hemidesmosomal components at the basal side of the cell. Using keratinocytes derived from patients lacking HD1/plectin, we now show that ligand-independent formation of hemidesmosomal clusters indeed requires HD1/plectin, in contrast to the ligand-dependent assembly of hemidesmosomes. No clustering of the (alpha)6(beta)4 integrin, or of the bullous pemphigoid antigens BP180 and BP230, was seen when HD1/plectin-deficient keratinocytes were plated on fibronectin or type IV collagen. In (β)4-deficient keratinocytes, expression of an interleukin 2 receptor (IL2R) transmembrane chimera containing the (beta)4 cytoplasmic tail with the mutation R1281W, which abrogates HD1/plectin binding, resulted in a diffuse distribution of the chimeric receptor. In contrast, a (beta)4(R1281W) mutant that can associate with (alpha)6 and bind ligand, was found to be directed to the basal surface of the cells, at sites where laminin-5 was deposited. In addition, this mutant induced clustering of BP180 and BP230 at these sites. Together, these results show that the formation of hemidesmosomes requires binding of either ligand or HD1/plectin to the (beta)4 integrin subunit. Intriguingly, we found that IL2R/(beta)4 chimeras become localized in pre-existing hemidesmosomes of HD1/plectin-deficient keratinocytes, and that this localization requires a domain in the (beta)4 cytoplasmic tail that is also required for HD1/plectin binding (residues 1115–1356). Because this part of (beta)4 lacks the BP180 binding site, and since we show in this study that it is unable to interact with the same part on another (beta)4 molecule, we suggest that the chimera becomes incorporated into hemidesmosomes of HD1/plectin-deficient keratinocytes by interacting with an as yet unidentified hemidesmosomal component.

Integrin binding specificity of laminin-10/11: laminin-10/11 are recognized by alpha 3 beta 1, alpha 6 beta 1 and alpha 6 beta 4 integrins

Laminin-10/11, the laminin isoforms containing the alpha 5 chain, are major components of basement membranes of many fetal and adult tissues. Laminin-10/11 purified from the conditioned medium of human lung carcinoma cells were potent in mediating adhesion of the carcinoma cells in an integrin alpha 3 beta 1-dependent manner. To further define the type(s) of integrins involved in cell adhesion to laminin-10/11, we examined the effects of a panel of function-blocking anti-integrin antibodies on the adhesion of different cell types to laminin-10/11. Although anti-integrin beta 1 antibody inhibited the adhesion of all cell types tested, anti-alpha 3 antibody inhibited the adhesion of carcinoma and glioma cells but not fibroblastic cells. Adhesion of fibroblastic cells was inhibited, however, by a combination of anti-alpha 3 and anti-alpha 6 antibodies, suggesting that both alpha 3 beta 1 and alpha 6 beta 1 integrins function as laminin-10/11 receptors in these cells. To explore this possibility, we examined the adhesion of K562 leukemic cells transfected with integrin alpha 3 or alpha 6 subunit to laminin-10/11 or other laminin isoforms. Laminin-10/11 were potent adhesive ligands for both the alpha 3 beta 11 and alpha 6 beta 1 transfectants, whereas laminin-5 was the preferred ligand for the alpha 3 beta 1 transfectants. Upon stimulation with the activating anti-integrin beta 1 antibody, both transfectants became more adherent to the substratum regardless of the type of laminins coated, although their preference for laminin isoforms remained unaltered. K562 cells transfected with alpha 6 and beta 4 subunits were also capable of adhering to laminin-10/11, indicating that integrin alpha 6 beta 4 is another receptor for laminin-10/11. Even with lung carcinoma cells, the alpha 6-containing integrins partly contributed to adhesion to laminin-10/11 at higher coating concentrations, although non-integrin receptor(s) might also be involved under such conditions. These results indicated that laminin-10/11 are potent and versatile adhesive ligands in basement membranes capable of binding to both alpha 3 beta 1 and alpha 6 beta 1 integrins with high avidity and also to alpha 6 beta 4 integrin.

Cost analysis of antibiotic prophylaxis for PEG

BACKGROUND

There are conflicting recommendations regarding the prophylactic use of antibiotics in patients undergoing placement of percutaneous endoscopic gastrostomy tubes. The purpose of this decision analysis was to assess the cost-effectiveness of antibiotic prophylaxis in percutaneous endoscopic gastrostomy.

METHODS

A decision tree was modeled using the data of 7 published prospective placebo-controlled trials. Infectious complications were classified as grade I (requiring local care), grade II (requiring intravenous antibiotics), or grade III (requiring surgery). Medication costs were estimated from the United States average wholesale prices of the 1998 Red Book. Physician and facility costs were estimated based on the 1998 Medicare costs. A one-way sensitivity analysis was performed by varying the probability rates of the complications associated with percutaneous endoscopic gastrostomy and the costs of their treatment.

RESULTS

The average cost of prophylactic antibiotics was $13.10. Antibiotic prophylaxis led to expected cost savings of $76.72 per percutaneous endoscopic gastrostomy. A sensitivity analysis suggested that antibiotic prophylaxis for percutaneous endoscopic gastrostomy was the preferred strategy unless the average probability of grade III complications dropped below an improbably low threshold value of 0.09%.

CONCLUSION

Antibiotic prophylaxis in percutaneous endoscopic gastrostomy is a cost-effective strategy.

Partial rescue of epithelial phenotype in integrin beta4 null mice by a keratin-5 promoter driven human integrin beta4 transgene

Integrin beta4 null mice exhibit extensive epidermal detachment, reminiscent of the human skin blistering disease junctional epidermolysis bullosa associated with pyloric atresia. Hemidesmosomes, the stable adhesion structures of squamous epithelia, are not formed in the absence of alpha6beta4. Null mutant mice die shortly after birth, but apart from their striking epithelial phenotype, no obvious developmental defects have been observed. To elucidate the cause of death in these mice, we generated transgenic mice with a heterologous construct consisting of the squamous epithelial-specific keratin-5 promoter and a human integrin beta4 subunit cDNA. The transgene was not expressed in the presence of endogenous beta4, probably as a result of competition for a limited pool of alpha6 subunits. In a beta4 null background, however, the transgene was expressed, and its expression pattern followed that of squamous epithelial-specific keratins. These rescued pups appeared healthy and ultrastructural analysis revealed that the interspecies heterodimer alpha6(mouse)/beta4(human) was sufficient to trigger the assembly of hemidesmosomes. After a variable period of up to 48 hours after birth these animals began to exhibit haemorrhages at the plantar and palmar areas. We observed the formation of small blisters and found that the transgene was not detectably expressed in this region, which is devoid of hair follicles. The rescued neonates became increasingly cyanotic and died soon after the onset of this phenomenon. We performed a developmental study of the expression of beta4 in the complete respiratory tract, but we found no correlation between the spatiotemporal distribution of beta4 and the onset of the respiratory insufficiency. It became clear, however, that there was a gradual detachment of squamous epithelia in the oral and nasal cavities which led to obstruction of the respiratory tract, suggesting that in beta4 null and rescued mice, neonatal death was a direct consequence of decreased adhesion properties of hairless squamous epithelia, rather than a developmental defect of the lungs.

At what age should a one-time only colonoscopy for screening of colorectal cancer be performed?

OBJECTIVE

To determine at what age the only screening colonoscopy during lifetime should be performed to achieve the highest yield.

METHODS

Medical decision analysis to calculate the loss in life years associated with mortality from colorectal cancer at different ages.

RESULTS

The expected loss in life years from colorectal cancer is highest between the ages 70 to 80 years, with a peak occurring at age 75. The length of protection provided by colonoscopy plus polypectomy is estimated to last 5-10 years after the procedure. A screening colonoscopy at age 65 would, thus, protect a subject from age 65 until age 70 or 75 years. Similarly, a screening colonoscopy at age 70 would protect the subject from age 70 until age 75 or 80 years.

CONCLUSIONS

The highest yield in life years by preventing death from colorectal cancer is achieved if the only colonoscopy per lifetime is scheduled between the ages of 65 and 70 years.

The unsolved problem of surveillance for colorectal cancer in ulcerative colitis

The association between long standing extensive ulcerative colitis and the increased risk for developing colorectal cancer suggests that surveillance by frequent and regular colonoscopies may provide a means for reducing cancer-related morbidity and mortality. A crude calculation suggests that such a surveillance program would also be cost effective. None of several clinical trials, however, has been able to provide unequivocal evidence in favour of surveillance. The major reason for this failure relates to the prohibitively large number of patients with ulcerative colitis who need to be followed over a prolonged time period before statistically sound results would be obtained. Because models of decision analyses themselves have to rely on medical evidence, they cannot provide a substitute for deficient clinical data. The issue of surveillance colonoscopy cannot be resolved by the available knowledge or analytical tools. Hopefully, new techniques of surveillance or even a cure for ulcerative colitis will render the question mute of whether or not to screen patients with ulcerative colitis by frequent colonoscopy.

Birth-cohort phenomenon in the time trends of mortality from ulcerative colitis

It has been suggested that the mortality trends of ulcerative colitis in England and Wales are shaped by an underlying birth-cohort phenomenon. This pattern implies that exposure to an environmental risk factor early in life plays a crucial role in the development of the disease. The authors tested whether the birth-cohort pattern is unique to British mortality statistics or a common feature of ulcerative colitis in western countries by using the vital statistics from England and Wales, Canada, Scotland, Switzerland, The Netherlands, and the United States. Ulcerative colitis death rates from the six countries were plotted against the periods of death or periods of birth. Mortality from ulcerative colitis increased in successive generations born throughout the second half of the 19th century. It peaked in subjects born between 1880 and 1890 and has declined since then. Strikingly similar patterns were found in the six countries and when women and men were analyzed separately. The birth-cohort pattern indicates that development of ulcerative colitis is strongly influenced by one or several environmental risk factors, which act during a short period early in life. In western countries, exposure to this risk has changed in a similar fashion.

Commonalities in the time trends of Crohn's disease and ulcerative colitis

OBJECTIVE

The analysis of the time trends of inflammatory bowel disease (IBD) is a powerful research tool to assess the contribution of environmental factors to its etiology and to gain insights about possible causative mechanisms. A previous study revealed a characteristic relationship between the time trends of mortality from Crohn's disease and ulcerative colitis. The present study aimed to test whether the most recent temporal patterns still corroborate the hypothesis of two interacting risk factors in the development of IBD. The time trends of IBD from six countries were checked for common features.

METHODS

Mortality data from Australia, Canada, England and Wales, the Netherlands, Sweden, and the United States were analyzed. Age- and sex-specific death rates, as well as total death rates, from Crohn's disease and ulcerative colitis were plotted against the period of death.

RESULTS

Mortality from ulcerative colitis decreased continuously during the past 40 years. Mortality from Crohn's disease increased between 1950 and the mid-1970's until reaching a similar level as mortality from ulcerative colitis. Since then the death rates of both diseases have followed a parallel time course. A similar behavior was found, if male and female data were analyzed separately. It could be also discerned in the time trends of each age group. The data from all six countries revealed identical temporal patterns.

CONCLUSIONS

The similar time trends of IBD from different countries support the hypothesis that identical causative mechanisms are responsible for the mortality and the occurrence of IBD among populations characterized by different political history and health care systems. The rapidity of the temporal changes implicates environmental agents in the etiology of both diseases. The relationships between the temporal changes of Crohn's disease and ulcerative colitis point at the existence of a shared risk factor responsible for the occurrence of both diseases, and at the existence of at least one additional factor, responsible for the expression of Crohn's disease alone.

Economic analysis of step-wise treatment of gastro-oesophageal reflux disease

BACKGROUND

To expose patients with gastro-oesophageal reflux disease (GERD) to the least amount of medication and to reduce health expenditures, it is recommended that their treatment is started with a small dose of an antisecretory or prokinetic medication. If patients fail to respond, the dose is increased in several consecutive steps or the initial regimen is changed to a more potent medication until the patients become asymptomatic. Although such treatment strategy is widely recommended, its impact on health expenditures has not been evaluated.

METHODS

The economic analysis compares the medication costs of competing medical treatment strategies, using two different sets of cost data. Medication costs are estimated from the average wholesale prices (AWP) and from the lowest discount prices charged to governmental health institutions. A decision tree is used to model the step-wise treatment of GERD. In a Monte Carlo simulation, all transition probabilities built into the model are varied over a wide range. A threshold analysis evaluates the relationship between the cost of an individual medication and its therapeutic success rate.

RESULTS

In a governmental health care system, a step-wise strategy saves on average $916 per patient every 5 years (range: $443-$1628) in comparison with a strategy utilizing only the most potent medication. In a cost environment relying on AWP, the average savings amount to $256 (-$206 to +$1561). The smaller the cost difference between two consecutive treatment steps, the longer one needs to follow the patients to reap the benefit of the small cost difference. However, even a small cost difference can turn into tangible cost savings, if a large enough fraction of GERD patients responds to the initial step of a less potent but also less expensive medication.

CONCLUSIONS

The economic analysis suggests that a step-wise utilization of increasingly more potent and more expensive medications to treat GERD would result in appreciable cost savings.

Outcome of surgical and endoscopic management of biliary pancreatitis

The aims of the study were to compare the outcomes of biliary pancreatitis after endoscopic and surgical treatment and define the demographic and clinical characteristics that affect the outcomes. All inpatients with biliary pancreatitis followed at hospitals of the Department of Veterans Affairs during 1988-1994 were included in a case-control study. Of 2075 patients with biliary pancreatitis, 650 were first treated by biliary endoscopy and 1425 by cholecystectomy. Compared with cholecystectomy, biliary endoscopy was associated with older age, admission to nonsurgical service, more complicated pancreatitis, and choledocholithiasis. Seventy-one patients died. Death occurred more often in older patients with multiple comorbid conditions and complications of biliary pancreatitis. Overall length of hospital stay was positively correlated with complications, choledocholithiasis, comorbidity, and deferment of endoscopic or surgical procedure. After adjusting for other confounding variables, both types of treatment resulted in similar death rates and lengths of hospitalization. In conclusion, compared with cholecystectomy, biliary endoscopy is chosen preferentially in older patients with choledocholithiasis or a complication of their pancreatitis. Despite such selection bias, biliary endoscopy results in similar outcomes as surgery. Early intervention by either strategy reduces the length of hospital stay.

Corpus gastritis is protective against reflux oesophagitis

BACKGROUND

Gastric acid is important in the pathogenesis of reflux oesophagitis. Acid production by the gastric corpus is reduced in corpus gastritis.

AIMS

To determine whether corpus gastritis protects against reflux oesophagitis.

METHODS

Patients presenting for elective oesophagogastroduodenoscopy were studied. Two biopsy specimens were taken from the antrum, corpus, and cardia and stained with haematoxylin/eosin and Diff-Quick II stains. The presence and severity of gastritis were graded according to a modified updated Sydney classification.

RESULTS

Of 302 patients, 154 had endoscopic signs of reflux oesophagitis. There was no difference between patients with and controls without oesophagitis in the overall infection rates with Helicobacter pylori. Acute or chronic corpus gastritis occurred less often in patients with than those without reflux oesophagitis. Compared with controls, corpus gastritis was less severe in patients with reflux oesophagitis. The presence of acute or chronic gastritis in the corpus was significantly correlated with either type of gastritis in other areas of the stomach. In a multivariate logistic regression, age, sex, smoking status, and the presence of chronic corpus gastritis all exerted a significant influence on the presence of reflux oesophagitis. Chronic corpus gastritis was associated with a 54% reduced risk for reflux oesophagitis.

CONCLUSIONS

While infection with H pylori alone may not affect the occurrence of reflux oesophagitis, the development of chronic corpus gastritis seems to be protective.

Is virtual colonoscopy a cost-effective option to screen for colorectal cancer?

OBJECTIVE

Computed tomography (CT) or magnetic resonance (MR) colonography is a new technique that uses data generated from CT or MR imaging to create two- and three-dimensional scans of the colon. It has been advocated to become the new primary technique of screening for colorectal cancer. The economic feasibility of such recommendation, however, has not yet been evaluated.

METHODS

The cost-effectiveness of two screening strategies using CT colonography or conventional colonoscopy was compared by computer models based on a Markov process. We supposed that a hypothetical population of 100,000 subjects aged 50 yr undergoes a screening procedure every 10 yr. Suspicious findings of CT colonography are worked-up by colonoscopy. After polypectomy, colonoscopy is repeated every 3 yr until no adenomatous polyps are found.

RESULTS

Under baseline conditions, screening by CT colonography costs $24,586 per life-year saved, compared with $20,930 spent on colonoscopy screening. The incremental cost-effectiveness ratios comparing CT colonography to no screening and colonoscopy to CT colonography were $11,484 and $10,408, respectively. Screening by colonoscopy remains more cost-effective even if the sensitivity and specificity of CT colonography both rise to 100%. For the two screening procedures to become similarly cost-effective, CT colonoscopy needs to be associated with an initial compliance rate 15-20% better or procedural costs 54% less than colonoscopy.

CONCLUSIONS

To become cost-effective and be able to compete with colonoscopy in screening for colorectal cancer, CT or MR colonography would need be offered at a very low price or result in compliance rates much better than those associated with colonoscopy.

Outcome of erosive reflux esophagitis after Nissen fundoplication

OBJECTIVE

The aim of this study was to compare the utilization of health care resources and long term outcome of erosive esophagitis in patients treated with and without open Nissen fundoplication.

METHODS

A population of 35,725 patients with erosive esophagitis was extracted from the computerized database of the US Department of Veterans Affairs. Subjects were stratified by severity of disease into erosive esophagitis alone versus erosive esophagitis complicated by esophageal ulcers or peptic strictures. During a mean follow-up period of 4.2 yr (range 1-12 yr), the consumption of health care resources, except for medications, was compared between case and control subjects treated with and without fundoplication, respectively.

RESULTS

Among patients with complicated erosive esophagitis, 5,064 control subjects were treated without, and 542 case subjects were treated with, fundoplication. Cases incurred less recurrence of esophageal erosions (controls: 56% vs cases: 46%), esophageal ulcers (38% vs 33%), and peptic strictures (43% vs 32%) during follow-up. Among patients with erosive esophagitis but no complications, 29,514 control subjects were treated without, and 605 case subjects were treated with, fundoplication. Cases did not experience any change in the recurrence of esophageal erosions (controls: 25% vs cases: 24%). Irrespective of treatment type, none of the case or control subjects with erosive esophagitis alone developed esophageal ulcers or peptic strictures during follow-up. Compared with controls, however, after fundoplication in erosive esophagitis alone, cases incurred more dysphagia (2.6% vs 4.6%), postsurgical syndromes (0.8% vs 1.7%), as well as more outpatient visits (34 vs 40 visits/patient) and outpatient procedures (2.7 vs 4.3 procedures/patient).

CONCLUSIONS

Fundoplication improves the clinical outcome of erosive esophagitis in patients with concomitant esophageal ulcers and strictures, but not in patients without such complications. Fundoplication does not reduce the consumption of health care resources.

Integrins: alternative splicing as a mechanism to regulate ligand binding and integrin signaling events

Integrins are a family of transmembrane proteins composed of heterodimers of alpha and beta subunits. With their extracellular domain they bind extracellular matrix proteins or other cell surface molecules, and their cytoplasmic domain binds to cytoskeletal and signaling proteins. Thus, they are in an ideal position to transfer information from the extracellular environment to the interior of the cell and vice versa. For several integrin subunits, alternative splicing of mRNA leads to variations in the sequence of both extracellular and cytoplasmic domains. Many integrin splice variants have specific expression patterns, but for some time, functional differences between these variants were not evident. Recent experiments using transfected cell lines and gene targeting of specific splice variants have contributed significantly to our understanding of the function of these splice variants. The results indicate that alternative splicing is a mechanism to subtly regulate the ligand binding and signaling activity of integrins.

Celiac sprue among US military veterans: associated disorders and clinical manifestations

The present study aimed to describe the clinical manifestations of celiac sprue related to malnutrition and to analyze the associations between celiac sprue and other diagnoses. A case-control study compared the occurrence of comorbid diagnoses in case and control subjects with and without celiac sprue, respectively. All patients with a primary or secondary diagnosis of celiac sprue (ICD-579.0) who were discharged from hospitals of the Department of Veterans Affairs between 1986 and 1995 were selected as case subjects. In a multivariate logistic regression analysis, the occurrence of celiac disease served as outcome variable, while age, gender, ethnicity, and the comorbid occurrences of other diagnoses served as predictor variables. A total of 458 individual patients with celiac sprue were identified. The data confirmed the known associations of celiac sprue with dermatitis herpetiformis, lactase deficiency, enlargement of lymph nodes, and lymphoma. Celiac sprue was also found to be statistically significantly associated with pancreatic insufficiency, Crohn's disease, functional bowel symptoms, chronic nonalcoholic hepatitis, and pulmonary eosinophilia. The nutritional manifestations associated with celiac disease included nutritional marasmus, cachexia, weight loss, hypocalcemia, osteoporosis, vitamin B-complex deficiency, and various types of iron- and vitamin-deficiency anemias. The large variety of complex associations clearly indicates that celiac sprue is a systemic disease that involves multiple organs and exceeds an isolated nutritional intolerance to gluten.

Reliability block diagrams to model disease management

BACKGROUND AND OBJECTIVES

Studies of diagnostic or therapeutic procedures in the management of any given disease tend to focus on one particular aspect of the disease and ignore the interaction between the multitude of factors that determine its final outcome. The present article introduces a mathematical model that accounts for the joint contribution of various medical and non-medical components to the overall disease outcome.

METHODS

A reliability block diagram is used to model patient compliance, endoscopic screening, and surgical therapy for dysplasia in Barrett's esophagus.

RESULTS

The overall probability of a patient with a Barrett's esophagus to comply with a screening program, be correctly diagnosed with dysplasia, and undergo successful therapy is 37%. The reduction in the overall success rate, despite the fact that the majority of components are assumed to function with reliability rates of 80% or more, is a reflection of the multitude of serial subsystems involved in disease management. Each serial component influences the overall success rate in a linear fashion. Building multiple parallel pathways into the screening program raises its overall success rate to 91%. Parallel arrangements render systems less sensitive to diagnostic or therapeutic failures.

CONCLUSIONS

A reliability block diagram provides the means to model the contributions of many heterogeneous factors to disease outcome. Since no medical system functions perfectly, redundancy provided by parallel subsystems assures a greater overall reliability.