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E Simchen

Publications and source records attributed to E Simchen.

At least 19 recordsLinked to original sources
PubMed2005

Evaluating survival model performance: a graphical approach.

In the last decade, many statistics have been suggested to evaluate the performance of survival models. These statistics evaluate the overall performance of a model ignoring possible variability in performance over time. Using an extension of measures used in binary regression, we propose a graphical method to depict the performance of a survival model over time. The method provides estimates of performance at specific time points and can be used as an informal test for detecting time varying effects of covariates in the Cox model framework. The method is illustrated on real and simulated data using Cox proportional hazard model and rank statistics.

Humans↗
PubMed2005

Increased risk of bloodstream and urinary infections in intensive care unit (ICU) patients compared with patients fitting ICU admission criteria treated in regular wards.

Critically ill patients, eligible for admission into intensive care units (ICUs), are often hospitalized in other wards due to a lack of ICU beds. Differences in morbidity between patients managed in ICUs and elsewhere are unknown, specifically the morbidity related to hospital-acquired infection. Patients fitting ICU admission criteria were identified by screening five entire hospitals on four separate days. Hospital infections within a 30-day follow-up period were compared in ICU patients and in patients on other wards using Kaplan-Meier curves. Residual differences in the patients' case mix between ICUs and other wards were adjusted for utilizing multivariate Cox models. Of 13415 patients screened, 668 were critically ill. The overall infection rates (per 100 patient-days) were 1.2 for bloodstream infection (BSI) and 1.9 for urinary tract infection (UTI). The adjusted hazard ratios in ICU patients compared with patients on regular wards were 3.1 (P<0.001) for BSI and 2.5 (P<0.001) for UTI. This increased risk persisted even after adjusting for the disparity in the number of cultures sent from ICUs compared with ordinary wards. No interdepartmental differences were found in the rates of pneumonia, surgical wound infections and other infections. Minimizing the differences between characteristics of patients hospitalized in ICUs and in other wards, and controlling for the higher frequency of cultures sent from ICUs did not eliminate the increased risk of BSI and UTI associated with admission into ICUs.

Aged↗
PubMed2001

Sociodemographic and clinical factors associated with low quality of life one year after coronary bypass operations: the Israeli coronary artery bypass study (ISCAB).

OBJECTIVES: We sought to examine the effect of sociodemographic characteristics and perioperative clinical factors 1 year after coronary bypass operations on low health-related quality of life. We also sought to assess the usefulness of an additional single question on overall health for identifying patients with low health-related quality of life. METHODS: This report is part of the Israeli coronary artery bypass study of 1994, in which every patient undergoing isolated coronary bypass grafting in Israel was included. The target population for this report comprised all survivors beyond 1 year who were 45 to 65 years of age. Patients were interviewed before the operations. Self-administered questionnaires regarding health-related quality of life (SF-36) were sent to 1724 patients who were successfully located 1 year postoperatively, and 1270 questionnaires were completed. Low health-related quality of life was defined as the lowest tertile of the distribution of scores for the 2 summary components of the SF-36 and the single question on overall health. Logistic models were constructed for each of the 3 outcomes. RESULTS: Female sex and low socioeconomic background were associated with low health-related quality of life in the logistic models. Other significant factors were symptoms of angina, sleep disturbances, hypertension, high severity of illness scores, hospital readmission, no rehabilitation, and hospitals with high perioperative mortality. Of the 3 study outcomes, the model for the single question on overall health was the most discriminating (C statistic = 0.76 vs 0.70 and 0.70, respectively). CONCLUSIONS: The study identifies patients who would most benefit from posthospitalization community support after bypass operations. Under circumstances of limited resources, these disadvantaged groups should be targeted as a priority. Encouraging participation in existing rehabilitation programs or introducing telephone hotlines could improve health-related quality of life after coronary bypass grafting without large investments.

Aged↗
PubMed2001

Is participation in cardiac rehabilitation programs associated with better quality of life and return to work after coronary artery bypass operations? The Israeli CABG Study.

OBJECTIVE: To explore the putative effect of cardiac rehabilitation programs on the 'health-related quality of life' and 'return to work' in pre-retirement patients one year after coronary artery bypass grafting. METHODS: Of the 2,085 patients aged 45-64 who survived one year after CABG and were Israeli residents, 145 (6.9%) had participated in rehabilitation programs. Of these, 124 (83%) who answered QOL questionnaires were individually matched with 248 controls by gender, age within 5 years, and the time the questionnaire was answered. All patients had full clinical follow-up including a pre-operative interview. The Short Form-36 QOL questionnaire as well as a specific questionnaire were mailed to surviving patients one year after surgery. Study outcomes included the scores on eight scales and two summary components of the SF-36, as well as 'return to work' and 'satisfaction with medical services' from the specific questionnaire. Analysis was done for matched samples. RESULTS: Cardiac rehabilitation participants had significantly higher SF-36 scores in general health, physical functioning, and social functioning. They had borderline significant higher scores in the physical summary component of the SF-36. The specific questionnaire revealed significantly better overall functioning, higher satisfaction with medical care, and higher rate of return to work. While participants in cardiac rehabilitation and their controls were similar in their socio-demographic and clinical profiles, participating patients tended to be more physically active and more fully employed than their controls. CONCLUSIONS: Rehabilitation participants had a self-perception of better HRQOL, most significantly in social functioning. Our findings of more frequent return to work and higher satisfaction with medical care should induce a policy to encourage participation in cardiac rehabilitation programs after CABG.

Case-Control Studies↗
PubMed2000

Sequential logistic models for 30 days mortality after CABG: pre-operative, intra-operative and post-operative experience--The Israeli CABG study (ISCAB). Three models for early mortality after CABG.

OBJECTIVES: The goal of this paper was to examine the added effect of operative and post-operative variables on 30 days mortality, in addition to patients' case-mix factors. SETTING AND DESIGN: A prospective study of 4835 patients, 95% of all Israeli patients who underwent coronary artery bypass grafting (CABG) in 1994. Information related to risk of death was collected at admission to hospital (preceding the operation), at time of the operation and in the immediate post-operative period. Deaths were independently ascertained. METHOD: Data collectors followed every patient from admission to discharge. Sequential logistic models were constructed for the 'case-mix', 'operative' and the 'post-operative' periods in chronological order. Each model incorporated and adjusted for the risk estimated at the previous point in time, by forcing individual risk scores. RESULTS: Significant pre-operative risk factors for 30 days mortality, in the case-mix model included mainly severity of illness characteristics, such as, left ventricular dysfunction and emergency admission, (c-statistic 78.8%). Model 2 (the 'operation' model) included in addition to the case-mix score, excessive duration of the operation per graft, bleeding, etc. (c-statistic 85.3%). The post-operative model showed the added effect of the post-operative factors such as low haemoglobin, additional surgery, and excessive time on respirator, (c-statistic 92.4%). CONCLUSIONS: The sequential analysis was an efficient method for updating patients' risk over time, where the number of events was small, relative to the number of risk factors. The addition of peri-operative factors increased significantly the predictive power of the model, adding clinical insights to the role of the hospital experience on 30 days mortality.

Adult↗
PubMed1999

Prediction of readmissions after CABG using detailed follow-up data: the Israeli CABG Study (ISCAB)

OBJECTIVE: To use detailed pre-discharge follow-up data to predict readmissions within 3 months after Coronary Artery Bypass Grafting (CABG). SETTINGS AND DESIGN: A prospective nationwide study (ISCAB) of 4,835 patients undergoing isolated CABG in Israel in 1994. Survivors of the initial hospitalization were candidates for the readmission study. METHODS: Patient information was prospectively collected from preoperative interviews and hospital follow-up. Readmissions' data were obtained from the National Hospital Admission Registry. Logistic and multinomial models were constructed for total and cause-specific readmissions, respectively. RESULTS: Of CABG survivors, 1,094 (24.1%) were rehospitalized within 3 months of the original surgery. Significant multivariate predictors of total readmissions included the following: preoperative co-morbidities; operative factors; immediate post-operative complications and socio-demographic characteristics as well as provider characteristics. However, the logistic model had low predictive power (c-statistic = 0.65). The heterogeneous reasons for readmissions were classified into specific serious cardiac diagnoses (19.0%), other cardiac reasons (35.4%), specific infections at the site of the operation (10.2%), other infections (7.3%), and various other reasons (23.0%). The multinomial model for cause-specific readmissions caused by either serious cardiac reasons or wound infection had a higher predictive value (c-statistics of 0.75, 0.72, respectively). CONCLUSIONS: Total readmissions after CABG in Israel were difficult to predict, even with an extensive pre-discharge follow-up data. We propose that reasons for readmission vary from true emergencies to nonspecific causes, with the latter related to a lack of support services in the community. We suggest that cause-specific rehospitalizations could be a better outcome for evaluating quality of care.

Aged↗
PubMed1998

A national study of postoperative mortality associated with coronary artery bypass grafting in Israel. ISCAB Consortium. Israel Coronary Artery Bypass Study.

BACKGROUND: Investigation of observed differences in outcomes among medical centers is of major interest to the medical community and the public and has a substantial impact on efforts to improve the quality of medical care. METHODS: This study analyzed data from consecutive patients who underwent isolated coronary artery bypass grafting at 14 medical centers. Data included demographic and clinical information, comorbidity, cardiac catheterization results, and 30-day postoperative vitality status. Logistic regression analysis was used to identify variables associated with mortality. An outlier hospital was defined as one having an observed mortality outside the 95% confidence interval boundaries around the expected mortality rate calculated, given the patient risk factors. RESULTS: The overall crude 30-day mortality rate for isolated coronary artery bypass grafting among the 4,835 patients in this study was 3.1%. The rate varied among centers, ranging from 0.85% to 7.05%. Predictors of 30-day mortality included advanced age, female sex, diabetes mellitus, poor left ventricular function, high creatinine level, high priority of operation, and three-vessel disease (with or without left main coronary artery disease). After adjustment for risk factors, two hospitals were defined as outliers. CONCLUSIONS: The observed disparity in early mortality among patients undergoing coronary artery bypass grafting is not due solely to differences in case mix.

Coronary Artery Bypass↗
PubMed1998

Use of antibiotic exposure to detect postoperative infections.

OBJECTIVE: To assess the utility of postoperative antibiotic exposure as an indicator of postoperative infection after coronary artery bypass graft surgery. DESIGN: We determined an optimal antibiotic exposure threshold by creating receiver operating characteristic curves. SETTING: Tertiary healthcare institution (United States); national sample (Israel). PATIENTS: 5,887 patients undergoing coronary artery bypass graft surgery. RESULTS: Postoperative antibiotic exposure with at least 9 days between the first and last dates of antibiotic administration, excluding the first postoperative day, had a sensitivity of 95% (261/276) and specificity of 85% (3,944/4,628) for identifying surgical-site infection, using as a gold standard surgical-site infections identified by conventional prospective surveillance or extrapolated from review of a sample of medical records. In contrast, using the same gold standard for surgical-site infections, the sensitivity of routine prospective surveillance alone was only 60%. The predictive value positive of the defined antibiotic exposure was 28% (261/945) for surgical-site infection and 60% (563/945) for any nosocomial infection. In the Israeli cohort, the sensitivity was 87% (74/85) and the specificity was 82% (735/898). CONCLUSION: Antibiotic exposure of sufficient duration and timing was more sensitive than conventional methods in detecting nosocomial infection and required substantially less effort to collect. Although the predictive value positive for surgical-site infection was only moderate, the majority of individuals identified this way had a nosocomial infection.

Antibiotic Prophylaxis↗
PubMed1997

Israeli women were at a higher risk than men for mortality following coronary bypass surgery.

As part of a national study of surgical departments is Israel, cardiac surgery patients undergoing open heart surgery between 1987 and 1989 were followed-up prospectively. Of these, 1,046 patients had coronary artery bypass grafting (CABG) and are the subject of this report. The six-months mortality after surgery was 12.9% among 202 women and 4.1% among 844 men. Female gender was an independent predictor of mortality even after controlling for the effect of 14 putative risk factors. The adjusted relative risk for mortality in women compared to men was 2.79 (1.5-5.2). In an attempt to understand this excessive mortality among women, a detailed analysis in one of the participating hospitals revealed differences associated with surgical technique by gender, such as proportion of patients with entirely venous grafting vs internal mammary artery grafts (IMA). Thirty percent of women vs 4.8% of men had entirely venous grafting. Adjusting the data for differences in the proportion of venous grafting has obliterated the difference in mortality between the genders in that hospital. We suggest that interventions to reduce mortality among women should involve a more careful choice of female candidates for CABG surgery, as well as introduction of modifications in the operating technique.

Adult↗
PubMed1996

Method for separating patient and procedural factors while analyzing interdepartmental differences in rates of surgical infections: the Israeli Study of Surgical Infection in Abdominal Operations.

The objective of this study was to develop a method for analyzing differences in the performance of hospitals with respect to outcome by separating patient factors from procedural factors. The setting included a prospective follow-up of a sample of 5571 patients undergoing all types of surgical procedures in general surgery departments of 11 hospitals (20 surgical departments) across Israel. Of these, 769 underwent surgery involving the opening of the bowel, and they are the subjects of this report. Our method consisted of a prospective follow-up by a nurse epidemiologist, including detailed clinical data from the day of admission to hospital discharge. Analysis was directed at identifying reasons for the observed variability in wound infections among departments. Observed rates were compared with "expected" rates calculated from a logistic model pooled over departments. An attempt was made to separate patient-inherent characteristics, such as age, sex, and diagnosis, from procedural factors, depicting the patient's experience during his hospitalization. Results indicated that the marked interdepartmental differences in the observed infection rates were not accounted for by differences in the "case mix" among departments. Procedural risk factors in this data set played the main role in explaining the observed variability among surgical departments. We conclude that the simple method presented here used the data pooled over departments to define the main risk determinants for infection in this data set. It separated intrinsic patient factors from procedural characteristics, and could be used in studies where the main interest is to compare institutions, and point at reasons behind the differences in outcomes.

Adult↗
PubMed1993

Determinants of wound infection in gastrointestinal operations: the Israeli study of surgical infections.

Risk factors for wound infection in operations involving the opening of the gastrointestinal (GI) tract, were explored in a prospective study. There were 813 consecutive operations performed during a period of 9-14 months in 11 Israeli hospitals. The total crude infection rate was 21.6%, and the respective rates for operations on the stomach, small bowel and colon were 14.8, 21.4 and 25.4%. Of 17 putative risk factors, the strongest predictor was the performance of 2 or more operations during the same admission. Other significant risk factors were: a diagnosis of intestinal obstruction or perforation, introduction of an open drain, emergency admission, age over 40, hospital stay prior to surgery 7 or more days, urinary catheter and infection on admission. Adjustment for these factors in a logistic regression model reduced the effect of the anatomical site of the operation (i.e. large bowel vs stomach) to a non-significant level.

Adult↗
PubMed1993

Cox regression models for intermediate events, with discharge from hospital as an example.

In studies of mortality or morbidity of hospitalized patients, discharge from hospital is an intermediate event between hospital experience and disease outcomes, as disease onset may occur after release from hospital. This study explored the role that discharge might have in risk for surgical infections after hernia repair operations, where follow-up continued for 1 month after operation, and 50% of infections occurred at home. Possible direct and interactive effects were evaluated in the presence of two major methodologic difficulties: waiting-time bias, because patients became candidates for home infections only after leaving the hospital, and selective discharge bias, because discharge carried much prognostic information. It was possible, using Cox models, to correct for the waiting-time bias, but the strong protective effect of termination of hospitalization on the risk for infection remained difficult to interpret. The strengths and limitations of various Cox models in dealing with these issues are discussed.

Adult↗
PubMed1992

Discharge from hospital and its effect on surgical wound infections. The Israeli Study of Surgical Infections (ISSI).

A multicenter study of 2846 consecutive hernia operations was conducted to identify risk factors for infections that occurred during the hospitalization and post-discharge from hospital. Operated patients were followed-up for 30 days after surgery, whether at home or still hospitalized, and half the wound infection episodes were found to occur at home. Risk factors for both in-hospital and post-discharge infections seemed to be influenced by; (a) the selective nature of discharge, (b) the differential effect some risk factors had on either early or late infections. On any given day, patients selected by the clinical team to remain in hospital were more "at risk" for infection than those who left. As a result, they had a better chance of being diagnosed as infected during hospitalization. By contrast, those who were discharged home were perceived as low risk for complications. Subsequent infections in these patients occurred either due to factors "causing" late infections, therefore, unappreciated at the time of discharge, or unknown risk factors. More study risk factors were associated with in-hospital than with post-discharge infections, especially those associated with "early" infections. The implications of these findings for future evaluations of medical care in hospitalized patients are discussed.

Female↗
PubMed1992

Differential effect of risk factors on early and late wound infections in patients undergoing herniorrhaphies.

In a prospective follow-up of 2846 patients who underwent hernia repair in 22 general surgery departments in Israel, factors affecting early or late infections were explored. Risk factors included inherent patient characteristics such as old age, ethnic group, and type of hernia prior to the surgery. Patient management factors included duration of the operation, use of urinary catheters, and use of drains. Of the 12 variables studied, only three had a constant effect during the entire 30-day follow-up. The other factors affected the occurrence of either early or late infections, but not both. For example, patients undergoing long operations, or from ethnic minorities, had a high rate of early infection, while those with special wound treatment (such as evacuation of hematomas) had high rates of late infection. It is postulated that factors present at the time of the operative incision tend to "cause" early infections, while factors that accumulate over time, or develop after leaving the operating theater, tend to affect late infections.

Adult↗
PubMed1991

An epidemic of waterborne Shigella gastroenteritis in Kibbutzim of western Galilee in Israel.

In an epidemic of Shigella sonnei gastroenteritis, probably waterborne, 1216 people were affected within three weeks, 302 of them members of communal settlements, the kibbutzim. A descriptive study of the epidemic in six affected kibbutzim in the area showed that the highest rates of diarrhoea occurred in a kibbutz that received its drinking water solely from the allegedly contaminated well. People at high risk within the kibbutzim were temporary visitors from Europe and the US (the volunteers), children aged 1 to 5 years, adult women, and children and their mothers in kibbutzim where the sleeping arrangements for the children was in 'children's houses'.

Adolescent↗
PubMed1991

Risk factors for infection in fracture war wounds (1973 and 1982 wars, Israel)

The development of post-surgical wound infection was compared in two groups of soldiers who sustained fractures or amputations on the battlefield during the first month of the 1982 and 1973 wars. Risk factors for the development of post-surgical wound infection were sought. In the 1982 group, numbering 184, the four variables independently associated with infection were multiple operations during the follow-up period; drains inserted in the first operation; extensive tissue loss; and blood transfusion during the first operation. For the 1973 group, numbering 130, the significant variables were multiple operations; amputations (highly correlated with extensive tissue loss); injury involving other body systems in addition to the fracture; and open drains. The high risk associated with open drains in both wars raises doubt about their usefulness. The main distinction between injuries of the two wars was the high prevalence (72.3%) of multi-system injuries in 1973 versus low prevalence (29.2%) in 1982. Overall infection rates were similar (30.5% and 31.5%), but infections at the site of the fracture were twice as high in 1982. Pseudomonas was the most common single species of bacteria isolated from infected wounds (26% in 1982, 33.6% in 1973). It appeared in the wounds relatively late, 10-14 days after admission.

Adult↗
PubMed1990

The Israeli Study of Surgical Infection of drains and the risk of wound infection in operations for hernia.

In a prospective follow-up study of 5,571 general surgical patients at 11 hospitals (23 departments) in Israel, 1,487 patients underwent operations for hernia (all types) and were screened daily for the development of postsurgical wound infection. Infection developed in 68 (4.6 per cent) at the site of the incision. Fourteen factors were analyzed for the presumed effect on the risk of infection; only four were significant in a multivariate model. Of these factors (old age, incarcerated or recurrent hernia, coexistent infection and drains), the introduction of drains had the strongest effect (relative risk equaled 4.1; p less than 0.001). Drains increased the risk in all the participating hospitals and in any category of patient. They prolonged the period a wound was susceptible to bacterial infection from nine to 16 days. The risk increased linearly with the duration of the drainage. The over-all proportion of patients who had a drain inserted was 19 per cent, with hospitals varying from 9 to 40 per cent of patients operated upon (p less than 0.001). Our findings suggest that the risk of an infection associated with drains may outweight their worth. Furthermore, there is no concensus among surgeons on the need for drains. Some surgeons use drains indiscriminately and others, rarely.

Aged↗