Identification of errors and factors associated with errors in data from electronic swine feeders.

Electronic swine feeders are used to automatically measure individual feed intake on group-housed pigs, but the resulting data contain errors caused by feeder malfunctions and animal-feeder interactions. The objectives of this study were to 1) develop criteria to identify errors in data from an electronic feeder that is predominant in the United States; 2) evaluate the frequency of errors in data from three consecutive experiments using the same feeders; and 3) identify factors associated with errors. Across experiments, data included 1,878,321 feed intake records (visits) on 1,721 pigs and 124 pens. Sixteen criteria were developed to detect errors in seven variables related to feed trough weights and times. Logistic regression was used to identify factors associated with the presence or absence of each error type in identified visits (visits where the feeder recognized a transponder) using a model that included the fixed effects of replicate, sex, linear and quadratic effects of day on test, and random effects of feeder within replicate, pig within feeder within replicate, test day within replicate, and week within feeder within replicate. Frequencies of error types in identified visits varied considerably within and between experiments. Errors in feed trough weights were more frequent than errors in time. Percentage of identified visits and of daily feed intake records with at least one error ranged from 4.3 to 18.7% and from 17.2 to 50.0%, respectively, and decreased from the first to the last experiment, reflecting the increasing ability of the managers to operate the feeders. Replicate, sex, test day, feeder within replicate, pig, and day within replicate affected the number of errors that occurred, but their effect varied among error types. Week-to-week variation within a feeder and replicate had the largest effect on number of errors, which was likely associated with feeder management. Results indicate that the frequency of errors in data from electronic swine feeders is substantial, but visits with errors can be identified and their frequency can be decreased by proper feeder management.

Cancer physicians' attitudes toward colorectal cancer follow-up.

BACKGROUND: The optimal follow-up strategy for colorectal cancer is unknown. MATERIALS AND METHODS: We surveyed all Canadian radiation oncologists, medical oncologists and surgeons specializing in colorectal cancer to assess their recommendations for follow-up after potentially curative treatment, the beliefs and attitudes underlying these practices, and the cost implications of different follow-up strategies. RESULTS: One hundred and sixty practitioners (58%) returned completed surveys. Most recommended clinical assessments every 3-4 months in the first 2 years including carcino-embryonic antigen testing, gradually decreasing in frequency over 5 years. Ninety per cent recommend a surveillance colonoscopy in the first year. The majority felt that specialist involvement in follow-up was important because of the increased opportunities for patients to contribute to research (76%) and teaching (73%). About half felt that specialists were more efficient at providing follow-up than primary care physicians, but these same physicians recommended significantly longer and more expensive follow-up routines on average than others. Primary care physicians were felt to be important allies, especially in managing the psychosocial concerns of patients. CONCLUSIONS: Surveillance practices are generally in keeping with published recommendations. Most specialists feel that they should remain involved in follow-up, but this may result in increased resource utilization.

Management of persistent or locally recurrent epidermoid cancer of the anal canal with abdominoperineal resection.

We retrospectively evaluated the outcome of 22 patients with epidermoid cancer of the anal canal who underwent surgical salvage after failure of primary chemoradiotherapy. Patients who required surgery had significantly more advanced T-stage than those who did not fail chemoradiotherapy. Eighteen patients failed surgical salvage. Invasion through the muscle wall of the bowel was present in 16 of 18 patients compared with two of four patients who have no evidence of disease (follow-up 5-10 years). Failure occurred only in the pelvis in 13 of the patients who died of disease. The mean time to death after surgery was 19 months. We confirm the overall poor results of conventional abdominoperineal resection in those patients who have failed previous therapy. Most failures occur in the pelvis. Transanorectal ultrasound and magnetic resonance imaging (MRI) may allow better selection of patients for exenterative procedures and identify those not amenable to successful salvage.

APC I1307K increases risk of transition from polyp to colorectal carcinoma in Ashkenazi Jews.

BACKGROUND & AIMS: The I1307K allele of the APC gene has been shown to confer a modestly elevated risk of colorectal cancer in the Ashkenazi Jewish population (relative risk, 1.5-1.7). However, it is unclear whether the alteration predisposes to adenomas and whether the genetic information can be used in clinical practice. To further address the pathogenic significance of I1307K, we offered both a genetic test and a screening program to individuals considered to be at increased risk for colorectal cancer. We compared the prevalence of polyps and their characteristics between carriers and noncarriers. METHODS: Invitations to participate in a DNA and colonoscopy screening program were mailed, together with a family questionnaire, to 3540 households forming the Jewish Community in Ottawa. The I1307K variant was analyzed in 242 eligible respondents who were selected because they had a personal or family history of colon cancer. Nearly 80% of these respondents (n = 189; age range, 32-83 years) consented to undergo a single colonoscopic examination. RESULTS: The overall carrier frequency of I1307K in the study group was 10.3%. A higher proportion of heterozygous gene carriers was found in the subgroup of colon cancer survivors (27%) than among asymptomatic individuals (8%, P < 0.02). A total of 59 polyps were identified in 44 subjects. Histologically confirmed adenomatous polyps were diagnosed in 11.8% of carriers and 12.8% of noncarriers (P > 0.5). No significant differences in polyp size, multiplicity, location, degree of villosity, or age-dependent prevalence were found between the 2 groups of participants. CONCLUSIONS: The high frequency of I1307K colorectal cancer patients found in the Ashkenazi Jewish community of Ottawa and the equivalent proportion of carriers and noncarriers who developed adenomatous polyps suggest that in this community, I1307K is associated with a significant predisposition to carcinoma but not adenoma.

The use of multiple imputation for the analysis of missing data.

This article provides a comprehensive review of multiple imputation (MI), a technique for analyzing data sets with missing values. Formally, MI is the process of replacing each missing data point with a set of m > 1 plausible values to generate m complete data sets. These complete data sets are then analyzed by standard statistical software, and the results combined, to give parameter estimates and standard errors that take into account the uncertainty due to the missing data values. This article introduces the idea behind MI, discusses the advantages of MI over existing techniques for addressing missing data, describes how to do MI for real problems, reviews the software available to implement MI, and discusses the results of a simulation study aimed at finding out how assumptions regarding the imputation model affect the parameter estimates provided by MI.

Primary prevention: what can you tell your patient?

Colorectal cancer, with its high incidence and significant morbidity and mortality, remains one of the leading causes of cancer-related deaths worldwide. Primary prevention of colorectal cancer may be more cost-effective and practical than secondary prevention. The primary prevention of colorectal cancer involves dietary and environmental modifications, chemoprevention, and in some cases prophylactic surgery.

Posterior predictive model checks for disease mapping models.

Disease incidence or disease mortality rates for small areas are often displayed on maps. Maps of raw rates, disease counts divided by the total population at risk, have been criticized as unreliable due to non-constant variance associated with heterogeneity in base population size. This has led to the use of model-based Bayes or empirical Bayes point estimates for map creation. Because the maps have important epidemiological and political consequences, for example, they are often used to identify small areas with unusually high or low unexplained risk, it is important that the assumptions of the underlying models be scrutinized. We review the use of posterior predictive model checks, which compare features of the observed data to the same features of replicate data generated under the model, for assessing model fitness. One crucial issue is whether extrema are potentially important epidemiological findings or merely evidence of poor model fit. We propose the use of the cross-validation posterior predictive distribution, obtained by reanalyzing the data without a suspect small area, as a method for assessing whether the observed count in the area is consistent with the model. Because it may not be feasible to actually reanalyze the data for each suspect small area in large data sets, two methods for approximating the cross-validation posterior predictive distribution are described.

Abnormal response to cholinergic stimulation in the circular muscle layer of the human colon in diverticular disease.

BACKGROUND: Diverticular disease is characterized by the occurrence of small herniations of the colonic mucosa, through the external muscle coats of the colon. The muscle wall is thickened, high intraluminal pressures can be recorded, and often constipation develops. The aim of the present study was to investigate whether an abnormality in the electric myogenic control activity could be found to help explain the etiology and symptoms of the disease. METHODS: Electric activity was studied by extracellular electrodes on tissues from both the circular and the longitudinal muscle of the colon from 12 patients. RESULTS: In tissues from 10 patients a distinctly abnormal response to cholinergic stimulation was observed. A characteristic development of bursts of action potentials did not develop; instead, slow-wave activity of relatively low frequency was maintained throughout the period of stimulation. This slow-wave activity showed a lack of synchronization. CONCLUSIONS: The results indicate that, in diverticular disease, local changes in electric activity occur that change the response to cholinergic stimulation. When this happens, development of periodic bursts of action potentials normally associated with propulsive activity do not develop, favoring segmental contractile activity associated with low-frequency slow-wave activity.

The association of bone mineral density with vitamin D receptor gene polymorphisms.

A recent meta-analysis of 16 publications suggested that bone mineral density (BMD) is not associated with vitamin D receptor (VDR) gene polymorphism (VDRGP) at the 0.05 significance level when a study with genotyping mistakes is excluded. We wished to determine whether 'positive' findings supporting the BMD-VDRGP association may be explained by chance, and what factors affect the outcomes of these studies. Seventy-five articles and abstracts on the association of VDRGP with BMD and related skeletal phenotypes published before January 1997 were identified. Twenty-three of 67 (34.3%) studies on spinal BMD and 22 of 51 (43.1%) on femoral neck BMD had found a BMD-VDRGP association at p < 0.05, significantly (p = 7 x 10(-14) for spinal BMD, p = 9 x 10(-16) for hip BMD) higher than the expected 5% false positive rate under the null hypothesis of 'no association'. 'Positive' results were more frequently observed in studies on females before the menopause than those on females after the menopause (p < 0.02) or on male and female subjects combined (p < 0.05) when skeletal phenotypes at any bone sites were considered. The 'positive rate' among studies was also influenced by the age range of subjects studied and by the inclusion of subjects with osteoporosis. It is concluded that: (1) BMD is associated with VDRGP with high levels of confidence and (2) non-genetic factors and genetic heterogeneity interfere with the detection of the effects of VDRGP on bone phenotypes.

Evaluation of 250 free-flap reconstructions after resection of tumours of the head and neck.

BACKGROUND: Microvascular free-tissue transfer is now the primary method of reconstruction in many centres. The aim of this study was to evaluate the applications, complications and limitations of free-flap reconstruction in a series of patients with tumours of the head and neck. METHODS: This study reviewed prospectively accessioned computerized records in a dedicated head and neck database. Patients treated between 1987 and 1995 with a minimum of a 1-year follow-up were reviewed. There were 242 patients with a mean age of 58 years (172 men and 70 women). The most common tumour sites were oral cavity (42%), oropharynx (32%) and hypopharynx (11%). Mucosal squamous carcinoma accounted for 87% of primary cancers. RESULTS: Among the 250 free flaps, the radial forearm flap (205) and free jejunum (25) predominated. There were 21 episodes of vascular occlusion (8%), failure of 10 flaps (4%) and two patients died peri-operatively (0.8%). A second free flap was used in five of 10 cases of flap failure. The fistula rate was 4.4% among 203 patients at risk for this complication, which comprised four of 178 forearm flaps and five of 25 free jejunal grafts. Four of 16 jaw reconstructions failed. CONCLUSIONS: A 96% success rate was achieved using free-tissue transfer for head and neck reconstruction. The overall complication rate was low but jaw reconstruction and free jejunal grafts posed the greatest problems because of failure of radial bone and fistulas, respectively. The radial forearm septocutaneous flap was very reliable and remains our mainstay for oral reconstruction.

Outcome of the pelvic pouch procedure in patients with prior perianal disease.

PURPOSE: There is concern that patients with presumed ulcerative colitis and significant perianal disease may in fact have Crohn's disease. Moreover, prior perianal disease may be an independent factor for poor outcome of the pelvic pouch. The aim of this study was to evaluate the effect of prior perianal disease on pelvic pouch outcome. METHODS: Between 1982 and 1994, 52 of 753 patients (6.9 percent) who had a pelvic pouch procedure were prospectively identified as having perianal disease. Outcome of the pelvic pouch of these 52 patients (Group I) were compared with the outcome of 701 pelvic pouch patients with no prior perianal disease (Group II). The perianal diseases identified in Group I were fissure-in-ano (17), perianal abscesses (13), fistula-in-ano (7), rectovaginal fistula (3), and significant hemorrhoids/skin tags (25). Eleven patients (21 percent) had more than one type of perianal disease. Twenty-seven patients (52 percent) required a total of 33 perianal operations for the different anal pathologies. RESULTS: Both groups were comparable for the following characteristics: age at time of pelvic pouch procedure, pathology (ulcerative colitis or indeterminate colitis), design of pouch, and type of ileoanal anastomosis (handsewn or stapled). An ileoanal anastomosis leak developed in 21 percent of patients (n = 11) in Group I vs. 11.4 percent (n = 80) in Group II (P < 0.05). Perianal postoperative complications occurred in 11.5 percent of patients (n = 6) in Group I vs. 1.7 percent (n = 12) in Group II (P < 0.05). Total pouch failure rate was not significantly different between the two groups (11.5 vs. 7.6 percent; P > 0.05). Crohn's disease was subsequently diagnosed in 1.9 vs. 2.7 percent (P > 0.05). Subgroup analysis of Group I patients showed no significant difference in outcome according to type of perianal lesion or a history of perianal surgery. CONCLUSION: Prior perianal disease significantly increases the risk of developing an ileoanal anastomotic leak and postoperative perianal complications. However, a pelvic pouch procedure may be an acceptable surgical alternative for selected ulcerative colitis patients with prior perianal disease because the overall pouch failure rate is not significantly increased.

Secondary sternal repair following median sternotomy using interosseous absorbable sutures and pectoralis major myocutaneous advancement flaps.

A consecutive series of 19 patients were treated for median sternotomy dehiscence by secondary sternal closure with interosseous absorbable sutures and superimposed pectoralis major myocutaneous advancement flaps. These patients were selected for this treatment only on the basis of the quality and quantity of remaining bone stock after debridement. Using this technique there have been no failures of primary therapy with a zero 30-day mortality rate. All patients have achieved good functional and aesthetic results with mechanically stable sternums, wounds confined to the chest and elimination of sepsis. This technique has the advantages of being simple, safe and relatively quick and avoids many of the inherent complications and disadvantages of other techniques and flaps commonly used in the management of this complication.

Nontraumatic subcutaneous emphysema in association with rectal carcinoma.

Nontraumatic subcutaneous emphysema is a rare complication of colorectal cancer. To the authors' knowledge, only eight cases have been reported to date. The initiating event was free colonic perforation in seven of the patients and contained colosubcutaneous fistula in the eighth. In nontraumatic subcutaneous emphysema typical fecal flora is cultured, whereas in nontraumatic gas gangrene, a different clinical entity that has a fulminant course, the bacteria are generally clostridial. The authors report a case of nontraumatic subcutaneous emphysema associated with rectal carcinoma and describe the associated computed tomography findings.

The Canadian Familial Adenomatous Polyposis Registry: past, present and future.

The advent of the molecular world opening up for familial adenomatous polyposis and other genetically predisposed cancers has now provided us with wonderful tools to study these diseases. The challenges, however, clearly remain to transfer discoveries in the laboratory to improvements in the care of these patients.

Genetic pre-disposition to colorectal cancer: Initiation of a prospective study in Eastern Ontario.

A pilot study which is part of both a larger provincial initiative and a network is in progress to address the question of genetic pre-disposition to non-polyposis colorectal cancer in eastern Ontario (population 1,200,000). It is modeled along a dual process of recruitment of at-risk individuals based on either prior documentation of family histories or a close relationship to patients who are hospitalized for colorectal cancer treatment. The molecular diagnostic and genetic counseling components of the project are in their initial phase of operation while follow-up strategies are being planned.