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1.  Comparison of imputation methods for missing laboratory data in medicine 
BMJ Open  2013;3(8):e002847.
Missing laboratory data is a common issue, but the optimal method of imputation of missing values has not been determined. The aims of our study were to compare the accuracy of four imputation methods for missing completely at random laboratory data and to compare the effect of the imputed values on the accuracy of two clinical predictive models.
Retrospective cohort analysis of two large data sets.
A tertiary level care institution in Ann Arbor, Michigan.
The Cirrhosis cohort had 446 patients and the Inflammatory Bowel Disease cohort had 395 patients.
Non-missing laboratory data were randomly removed with varying frequencies from two large data sets, and we then compared the ability of four methods—missForest, mean imputation, nearest neighbour imputation and multivariate imputation by chained equations (MICE)—to impute the simulated missing data. We characterised the accuracy of the imputation and the effect of the imputation on predictive ability in two large data sets.
MissForest had the least imputation error for both continuous and categorical variables at each frequency of missingness, and it had the smallest prediction difference when models used imputed laboratory values. In both data sets, MICE had the second least imputation error and prediction difference, followed by the nearest neighbour and mean imputation.
MissForest is a highly accurate method of imputation for missing laboratory data and outperforms other common imputation techniques in terms of imputation error and maintenance of predictive ability with imputed values in two clinical predicative models.
PMCID: PMC3733317  PMID: 23906948
2.  Patient reported symptoms during an ulcerative colitis flare: A Qualitative Focus Group Study 
It has been assumed that the symptoms measured in disease activity indices for ulcerative colitis reflect those symptoms that patients find useful in evaluating the severity of a disease flare. In this qualitative focus group study, we aimed to identify which symptoms are important to patients and to compare these symptoms with a comprehensive list of commonly measured symptoms to determine/evaluate whether the patient-reported important symptoms are represented in current disease activity indices for ulcerative colitis. Patients in this sample confirmed 15 symptoms but not 11 other symptoms found in common ulcerative colitis activity indices. Patients identified an additional 14 symptoms not included in commonly used ulcerative colitis activity indices, which they believed to be important in evaluating the onset or severity of an ulcerative colitis flare. Current indices capture only a portion of the clinical symptoms that are important to patients in an ulcerative colitis flare, and may neither accurately measure nor fully reflect patients’ experience of ulcerative colitis. These findings present an opportunity to develop better patient-centered measures of ulcerative colitis.
PMCID: PMC3193174  PMID: 19194304
focus groups; inflammatory bowel disease; patient-reported outcomes; qualitative research; symptom domains; ulcerative colitis
4.  Clinical yield of diagnostic ERCP in orthotopic liver transplant recipients with suspected biliary complications 
Background and aims
Diagnostic endoscopic retrograde cholangiopancreatography (ERCP) is commonly performed for the evaluation of biliary complications after orthotopic liver transplantation (OLT). This practice is contrary to national trends towards reserving ERCP for therapeutic purposes. Our aim was to evaluate the clinical yield and complications of diagnostic ERCP in OLT recipients.
In this retrospective study, 165 OLT recipients who underwent ERCP between 1/2006 and 12/2010 at the University of Michigan were divided into 2 groups: 1) therapeutic ERCP group (T-ERCP) if they met pre-specified criteria that suggested a high likelihood of endoscopic intervention, and 2) diagnostic ERCP group (D-ERCP) if they had a clinical suspicion of biliary disease but did not meet any criteria. The two groups were compared with regard to the proportion of subjects in each group who underwent a high-yield ERCP, defined as a procedure that resulted in a clinically important intervention that modified disease course.
66.3% of diagnostic ERCPs were classified as high-yield, compared to 90.1% of therapeutic ERCPs (p<0.001). Serious complications were infrequent in both groups. A survey of practitioners caring for OLT recipients suggested that the rate of high-yield D-ERCP seen in this study is congruent with that considered acceptable in clinical practice.
Although T-ERCP was more likely to reveal a pathologic process requiring intervention, diagnostic ERCP appears to be an acceptable clinical strategy in OLT recipients because of the high likelihood of a high-yield study and the low rate of serious complications.
PMCID: PMC3900243  PMID: 22888069
All appear in the title
5.  A Primer on Effectiveness and Efficacy Trials 
Although efficacy and effectiveness studies are both important when evaluating interventions, they serve distinct purposes and have different study designs. Unfortunately, the distinction between these two types of trials is often poorly understood. In this primer, we highlight several differences between these two types of trials including study design, patient populations, intervention design, data analysis, and result reporting.
PMCID: PMC3912314  PMID: 24384867
6.  A Primer on Predictive Models 
Prediction research is becoming increasing popular; however, the differences between traditional explanatory research and prediction research are often poorly understood, resulting in a wide variation in the methodologic quality of prediction research. This primer describes the basic methods for conducting prediction research in gastroenterology and highlights differences between traditional explanatory research and predictive research.
PMCID: PMC3912317  PMID: 24384866
7.  Spironolactone and colitis: Increased mortality in rodents and in humans 
Inflammatory Bowel Diseases  2011;18(7):1315-1324.
Background and Methods
Crohn’s disease causes intestinal inflammation leading to intestinal fibrosis. Spironolactone is an anti-fibrotic medication commonly used in heart failure to reduce mortality. We examined whether spironolactone is anti-fibrotic in the context of intestinal inflammation. In vitro, spironolactone repressed fibrogenesis in TGFβ-stimulated human colonic myofibroblasts. However, spironolactone therapy significantly increased mortality in two rodent models of inflammation-induced intestinal fibrosis, suggesting spironolactone could be harmful during intestinal inflammation. Since IBD patients rarely receive spironolactone therapy, we examined whether spironolactone use was associated with mortality in a common cause of inflammatory colitis, Clostridium difficile infection (CDI).
Spironolactone use during CDI infection was associated with increased mortality in a retrospective cohort of 4008 inpatients (15.9% vs. 9.1%, n=390 deaths, p<0.0001). In patients without liver disease, the adjusted OR for inpatient mortality associated with 80 mg spironolactone was 1.99 (95% CI: 1.51 – 2.63) In contrast to the main effect of spironolactone mortality, multivariable modeling revealed a protective interaction between liver disease and spironolactone dose. The adjusted odds ratio for mortality after CDI was 1.96 (95% CI: 1.50 – 2.55) for patients without liver disease on spironolactone vs. 1.28 (95% CI: 0.82 – 2.00) for patients with liver disease on spironolactone, when compared to a reference group without liver disease or spironolactone use.
We propose that discontinuation of spironolactone in patients without liver disease during CDI could reduce hospital mortality by 2-fold, potentially reducing mortality from CDI by 35,000 patients annually across Europe and the US.
PMCID: PMC3288762  PMID: 22081497
8.  Effect of Flexible Sigmoidoscopy-Based Screening on Incidence and Mortality of Colorectal Cancer: A Systematic Review and Meta-Analysis of Randomized Controlled Trials 
PLoS Medicine  2012;9(12):e1001352.
A systematic review and meta-analysis of randomized trials conducted by B. Joseph Elmunzer and colleagues reports that that flexible sigmoidoscopy-based screening reduces the incidence of colorectal cancer in average-risk patients, as compared to usual care or no screening.
Randomized controlled trials (RCTs) have yielded varying estimates of the benefit of flexible sigmoidoscopy (FS) screening for colorectal cancer (CRC). Our objective was to more precisely estimate the effect of FS-based screening on the incidence and mortality of CRC by performing a meta-analysis of published RCTs.
Methods and Findings
Medline and Embase databases were searched for eligible articles published between 1966 and 28 May 2012. After screening 3,319 citations and 29 potentially relevant articles, two reviewers identified five RCTs evaluating the effect of FS screening on the incidence and mortality of CRC. The reviewers independently extracted relevant data; discrepancies were resolved by consensus. The quality of included studies was assessed using criteria set out by the Evidence-Based Gastroenterology Steering Group. Random effects meta-analysis was performed.
The five RCTs meeting eligibility criteria were determined to be of high methodologic quality and enrolled 416,159 total subjects. Four European studies compared FS to no screening and one study from the United States compared FS to usual care. By intention to treat analysis, FS-based screening was associated with an 18% relative risk reduction in the incidence of CRC (0.82, 95% CI 0.73–0.91, p<0.001, number needed to screen [NNS] to prevent one case of CRC = 361), a 33% reduction in the incidence of left-sided CRC (RR 0.67, 95% CI 0.59–0.76, p<0.001, NNS = 332), and a 28% reduction in the mortality of CRC (relative risk [RR] 0.72, 95% CI 0.65–0.80, p<0.001, NNS = 850). The efficacy estimate, the amount of benefit for those who actually adhered to the recommended treatment, suggested that FS screening reduced CRC incidence by 32% (p<0.001), and CRC-related mortality by 50% (p<0.001).
Limitations of this meta-analysis include heterogeneity in the design of the included trials, absence of studies from Africa, Asia, or South America, and lack of studies comparing FS with colonoscopy or stool-based testing.
This meta-analysis of randomized controlled trials demonstrates that FS-based screening significantly reduces the incidence and mortality of colorectal cancer in average-risk patients.
Please see later in the article for the Editors' Summary
Editor's Summary
Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. Regular CRC screening has been shown to reduce the risk of dying from CRC by 16%, and CRC screening can identify early stage cancers in otherwise healthy people, which allows for early treatment and management of the disease. Screening for colorectal cancer is frequently performed using a flexible sigmoidoscopy (FS), which is a thin, flexible tube with a tiny camera and light on the end, allowing a doctor to look at the inside wall of the bowel and remove any small growths or polyps. Although screening may detect early cancers, the life-saving and health benefits of screening are uncertain because the polyp may not necessarily progress. This could lead to anxiety and unnecessary interventions and treatments amongst those screened. Randomized controlled trials (RCTs) are needed to determine all of the risks involved in cancer screenings, however the guidelines that recommend FS-based screening do not rely upon RCT data. Recently, the results of four large-scale RCTs evaluating FS screening for CRC have been published. The conflicting results with respect to the incidence and mortality of CRC in these studies have called into question the effectiveness of endoscopic screening.
Why Was This Study Done?
The results of RCTs measuring the risks and outcomes of CRC screening have shown varying estimates of the benefits of using FS screening. If better estimates of the risks and benefits of FS screening are developed, then the current CRC screening guidelines may be updated to reflect this new information. In this study, the authors show the results of a meta-analysis of published RCTs, which more precisely estimates the effects of FS-based screening on the incidence and mortality of colorectal cancer.
What Did the Researchers Do and Find?
The researchers used the Medline and Embase databases to find relevant studies from 1966 to May 28, 2012. After screening 3,319 citations and 29 potentially relevant articles, five RCTs of high methodologic quality and 416,159 total subjects evaluating the effect of FS screening on the incidence and mortality of CRC were identified. The data were extracted and random effects meta-analysis was performed. The meta-analysis revealed that FS-based screening was associated with an 18% relative risk reduction in the incidence of CRC (0.82, 95% CI 0.73–0.91, p<0.001, number needed to screen (NNS) to prevent one case of CRC = 361), a 33% reduction in the incidence of left-sided CRC (RR 0.67, 95% CI 0.59–0.76, p<0.001, NNS = 332), and a 28% reduction in the mortality of CRC (RR 0.72, 95% CI 0.65–0.80, p<0.001, NNS = 850). The amount of benefit for those who adhered to the recommended treatment suggested that FS screening reduced CRC incidence by 32% (p<0.001), and CRC-related mortality by 50% (p<0.001).
What Do These Findings Mean?
This meta-analysis of RCTs evaluating the effect of FS on CRC incidence and mortality demonstrates that a FS-based strategy for screening is very effective in reducing the incidence and mortality of CRC in patients. The current recommendations for endoscopic screening are based on observational studies, which may not accurately reflect the effect of FS-based screening on the incidence and mortality of CRC. Here, the authors performed a systematic review and meta-analysis of five recent RCTs to better estimate the true effect of FS-based screening on the incidence and mortality of CRC. Thus, the results of this meta-analysis may affect health policy, and directly impact patients and clinicians.
Additional Information
Please access these Web sites via the online version of this summary at
Cancer research UK provides comprehensive information about screening for colorectal cancers as does the UK National Screening Committee
PubMed Health has general information about colon cancer
The National Cancer Institute also has comprehensive resources on colorectal cancer and treatment
The Mayo Clinic provides an overview of all aspects of colon cancer
PMCID: PMC3514315  PMID: 23226108
9.  A Randomized Trial of Rectal Indomethacin to Prevent Post-ERCP Pancreatitis 
The New England Journal of Medicine  2012;366(15):1414-1422.
Preliminary research suggests that rectally administered nonsteroidal antiinflammatory drugs may reduce the incidence of pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP).
In this multicenter, randomized, placebo-controlled, double-blind clinical trial, we assigned patients at elevated risk for post-ERCP pancreatitis to receive a single dose of rectal indomethacin or placebo immediately after ERCP. Patients were determined to be at high risk on the basis of validated patient- and procedure-related risk factors. The primary outcome was post-ERCP pancreatitis, which was defined as new upper abdominal pain, an elevation in pancreatic enzymes to at least three times the upper limit of the normal range 24 hours after the procedure, and hospitalization for at least 2 nights.
A total of 602 patients were enrolled and completed follow-up. The majority of patients (82%) had a clinical suspicion of sphincter of Oddi dysfunction. Post-ERCP pancreatitis developed in 27 of 295 patients (9.2%) in the indomethacin group and in 52 of 307 patients (16.9%) in the placebo group (P = 0.005). Moderate-to-severe pancreatitis developed in 13 patients (4.4%) in the indomethacin group and in 27 patients (8.8%) in the placebo group (P = 0.03).
Among patients at high risk for post-ERCP pancreatitis, rectal indomethacin significantly reduced the incidence of the condition. (Funded by the National Institutes of Health; number, NCT00820612.)
PMCID: PMC3339271  PMID: 22494121
10.  Systematic Review: Pancreatic enzyme treatment of chronic pancreatitis 
Pancreatic enzyme supplementation is standard treatment for malabsorption due to chronic pancreatitis. The FDA recently required all manufacturers to submit New Drug Applications (NDAs) to continue to market these agents because published data demonstrated variation in formulation, bioavailability, and shelf-life while providing limited data about efficacy and safety.
To systematically review the design and results of randomized, parallel-design trials of pancreatic enzyme supplements in chronic pancreatitis patients with steatorrhea.
A computer-assisted search of MEDLINE and EMBASE was performed to identify relevant studies. Two authors performed duplicate data extraction on study design, improvement in coefficient of fat absorption (CFA), diarrhea, and adverse events using pre-specified forms. Agreement between investigators for data extraction was greater than 95%.
Of 619 articles found through literature searching, 20 potentially relevant articles were identified and 4 manuscripts met inclusion criteria. No studies performed head-to-head comparisons of different supplements. Enzyme supplementation is more likely to improve CFA compared to placebo, but fat malaborption remained abnormal. Important differences in patient population, study endpoint, study design, pancreatic enzyme dosage, and measurement of CFA were present across trials which precluded comparison of different agents.
Enzyme supplementation improves CFA compared to placebo but may not abolish steatorrhea.
PMCID: PMC3462488  PMID: 19035969
Pancreas; Enzyme; Malabsorption
11.  Identification of symptom domains in ulcerative colitis that occur frequently during flares and are responsive to changes in disease activity 
Ulcerative colitis disease activity is determined by measuring symptoms and signs. Our aim was to determine which symptom domains are frequent and responsive to change in the evaluation of disease activity, which are those defined by three criteria: 1) they occur frequently during flares; 2) they improve during effective therapy for ulcerative colitis; and 3) they resolve during remission.
Twenty-eight symptom domains, 16 from standard indices and 12 novel domains identified by ulcerative colitis patient focus groups, were evaluated. Sixty subjects with ulcerative colitis were surveyed, rating each symptom on the three criteria with a 100 mm Visual Analogue Scale. Frequent and responsive symptoms were defined a priori as those whose median Visual Analogue Scale rating for all 3 criteria was significantly greater than 50.
Thirteen of the 28 symptom domains were identified as both frequent in ulcerative colitis flares and responsive to changes in disease activity. Seven of these 13 symptom domains were novel symptoms derived from ulcerative colitis patient focus groups including stool mucus, tenesmus, fatigue, rapid postprandial bowel movements, and inability to differentiate liquid or gas from solid stool when rectal urgency occurs. Ten of the 16 symptom domains from standard indices were either infrequent or unresponsive to changes in disease activity.
Only some of the symptoms of ulcerative colitis that are important to patients are included in standard indices, and several symptoms currently measured are not frequent or responsive to change in ulcerative colitis patients. Development of survey measures of these symptom domains could significantly improve the assessment of disease activity in ulcerative colitis.
PMCID: PMC2559827  PMID: 18803870

Results 1-11 (11)