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Results for “Propensity Score”

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PubMed2005

Nonresponse bias in a survey of patient perceptions of hospital care.

BACKGROUND: Incomplete participation is of particular concern for surveys of patient perceptions of care because patients who have negative opinions may be least likely to participate. OBJECTIVE: We sought to examine indirect evidence of nonresponse bias. DESIGN: We re-analyzed data from a cross-sectional patient survey. SUBJECTS: Our subjects were patients discharged from a Swiss hospital (n = 2156). MEASURES: We measured the following: (1) an observed problem score, based on 15 key items of the Picker Patient Experience questionnaire, (2) a predicted problem score, and (3) a participation propensity score. The latter scores were computed for all eligible patients, including those who did not return the survey, from routinely available baseline data. RESULTS: The participation rate was 70% (n = 1518), and the mean problem score was 29.9 (SD 23.8). Early respondents reported significantly fewer problems than late respondents (28.6 versus 32.9, P = 0.001). Participation propensity scores were progressively lower in early respondents (mean 74.2), late respondents (70.7), and nonrespondents (63.9, P < 0.001); the pattern was similar for predicted problem scores (early respondents: 29.5; late respondents: 30.5; nonrespondents: 33.4, P < 0.001). The propensity to participate was negatively associated with the problem score (Pearson r = -0.19). Finally, predictors of participation were similar to predictors of problem scores. CONCLUSIONS: The tendency to participate in the survey was negatively associated with the report of problems during hospitalization. Nevertheless, increasing participation from 30% to 70% had only a modest influence on the final conclusions of the survey.

Adolescent↗

PubMed2005

Outcomes of infection in nursing home residents with and without early hospital transfer.

OBJECTIVES: To compare outcomes of infection in nursing home residents with and without early hospital transfer. DESIGN: Observational cohort study. SETTING: Fifty-nine nursing homes in Maryland. PARTICIPANTS: Two thousand one hundred fifty-three individuals admitted to nursing homes between 1992 and 1995. MEASUREMENTS: Incident infection was recorded when a new infectious diagnosis was documented in the medical record or nonprophylactic antibiotic therapy was prescribed. Early hospital transfer was defined as transfer to the emergency department or admission to the hospital within 3 days of infection onset. Infection, resident, and facility characteristics were entered into a multivariate model to create a propensity score for early hospital transfer. Association between early hospital transfer and outcomes of infection, namely pressure ulcers and death between Days 4 and 34 after infection onset, were examined, controlling for propensity score. RESULTS: Four thousand nine hundred ninety infections occurred in 1,301 residents. Genitourinary (28%), skin (19%), upper respiratory (13%), and lower respiratory (12%) were the most common types. Three hundred seventy-five episodes in which residents survived 3 days (7.6%) resulted in early hospital transfer. In multivariate regression, individuals with early hospital transfer had higher mortality (odds ratio (OR) 1.44, 95% confidence interval (CI)=1.04-1.99) and, in 1-month survivors, a greater occurrence of pressure ulcers (OR 1.61, 95% CI=1.17-2.20) than those without, after adjusting for propensity score. CONCLUSION: Using observational data and propensity score methods, outcomes were worse in nursing home residents transferred to the hospital within 3 days of infection onset than in those who remained in the nursing home.

Aged↗

PubMed2005

Effect of peri-operative red blood cell transfusion on 30-day and 1-year mortality following coronary artery bypass surgery.

OBJECTIVE: The purpose of this study was to examine the effect of peri-operative red blood cell (RBC) transfusion on 30-day and 1-year mortality following coronary artery bypass grafting (CABG). METHODS: We retrospectively analysed 3024 consecutive patients who underwent isolated CABG between January 1999 and December 2001. Patient records were linked to the National Strategic Tracing Service, which records all mortality in the UK. Thirty-day and 1-year mortality were derived from Kaplan-Meier curves. Confounding variables were controlled for by constructing a propensity score for the probability of receiving a transfusion from core patient characteristics including the lowest recorded laboratory haemoglobin (LL Hb) from a clinical chemistry database (C statistic 0.81). The propensity score and the comparison variable (transfusion versus no transfusion) were included in a Cox proportional hazards analysis, allowing calculation of adjusted hazard ratios (HR) and Kaplan-Meier survival curves. RESULTS: Nine hundred and forty (31.1%) patients received RBC transfusion during or within 72h of surgery. Predictors of the need for transfusion were LL Hb and lower body mass index, use of cardiopulmonary bypass, female sex, number of grafts, renal dysfunction, increased age, extent of disease, and prior CABG; these factors were all included in the propensity score. After 1-year of follow-up, 122 (4.03%) deaths occurred. The crude HR for 1-year mortality in patients transfused was 3.0 (P<0.001). After adjusting for the propensity score, re-operation for bleeding, peri-operative blood loss and post-operative complications, the adjusted 30-day mortality was 1.9% in transfused patients compared to 1.1% in patients not transfused (P<0.05). The adjusted HR for 1-year mortality in patients transfused was 1.88 (P<0.01). CONCLUSIONS: Peri-operative RBC transfusion after CABG is associated with an increased risk of mortality during a 1-year follow-up period, with a large proportion of deaths occurring within 30-days.

Aged↗

PubMed2004

Calcium antagonists are associated with reduced mortality after cardiac surgery: a propensity analysis.

OBJECTIVES: Observational studies have questioned the effectiveness of perioperative calcium channel blockers but failed to correct for selection biases. We therefore performed a prospective observational cohort study of the effects of calcium channel blockers on cardiac surgical mortality. A propensity score technique was used for risk adjustment. METHODS: We identified 6619 patients who underwent nontransplant cardiac surgery at the Toronto General Hospital (Toronto, Ontario, Canada) between May 1999 and December 2001. Propensity scores for calcium channel blocker use were constructed for the entire sample and for the subgroup (n = 5222) that underwent coronary artery bypass grafting. The calcium channel blocker adjusted odds ratio for in-hospital mortality after cardiac surgery was determined by using multiple logistic regression and propensity matched-pairs analyses. A subgroup analysis was performed for patients who underwent coronary artery bypass grafting: the calcium channel blocker adjusted odds ratio for mortality was determined by using propensity score matched-pairs analyses. RESULTS: Calcium channel blockers were associated with significantly reduced cardiac surgical mortality after adjustment with both multiple logistic regression (odds ratio, 0.56; 95% confidence interval, 0.33-0.94; P =.028) and propensity score matched-pairs analyses (odds ratio, 0.56; 95% confidence interval, 0.32-0.98; P =.042). Calcium channel blockers were also associated with reduced mortality (odds ratio, 0.48; 95% confidence interval, 0.23-0.98; P =.044) among patients who underwent coronary artery bypass grafting. CONCLUSIONS: After adjustment for baseline differences, calcium channel blockers were associated with significantly reduced mortality after cardiac surgery. This benefit also extends to the subgroup that underwent coronary artery bypass grafting. A large randomized controlled trial of perioperative calcium channel blockers is therefore warranted.

Adrenergic beta-Antagonists↗

PubMed1999

Increased risk of death in patients with do-not-resuscitate orders.

BACKGROUND: Whereas studies have shown higher mortality rates in patients with do-not-resuscitate (DNR) orders, most have not accounted for confounding factors related to the use of DNR orders and/or factors related to the risk of death. OBJECTIVE: To determine the relationship between the use of DNR orders and in-hospital mortality, adjusting for severity of illness and other covariates. DESIGN: Retrospective cohort study. PATIENTS: There were 13,337 consecutive stroke admissions to 30 hospitals in 1991 to 1994. MEASURES: To decrease selection bias, propensity scores reflecting the likelihood of a DNR order were developed. Scores were based on nine demographic and clinical variables independently related to use of DNR orders. The odds of death in patients with DNR orders were then determined using logistic regression, adjustment for propensity scores, severity of illness, and other factors. RESULTS: DNR orders were used in 22% (n = 2,898) of patients. In analyses examining DNR orders written at any time during hospitalization, unadjusted in-hospital mortality rates were higher in patients with DNR orders than in patients without orders (40% vs. 2%, P<0.001); the adjusted odds of death was 33.9 (95% CI, 27.4-42.0). The adjusted odds of death remained higher in analyses that only considered orders written during the first 2 days (OR 3.7; 95% CI, 3.2-4.4) or the first day (OR 2.4; 95% CI, 2.0-2.9). In stratified analyses, adjusted odds of death tended to be higher in patients with lower propensity scores. CONCLUSION: The risk of death was substantially higher in patients with DNR orders after adjusting for propensity scores and other covariates. Whereas the increased risk may reflect patient preferences for less intensive care or unmeasured prognostic factors, the current findings highlight the need for more direct evaluations of the quality and appropriateness of care of patients with DNR orders.

Aged↗

PubMed2006

Effect of risk-adjusted, non-dialysis-dependent renal dysfunction on mortality and morbidity following coronary artery bypass surgery: a multi-centre study.

OBJECTIVE: As little is known about the impact of non-dialysis-dependent renal dysfunction on short- and mid-term outcomes following coronary surgery we have conducted a large multi-centre study comparing patients with no history of renal dysfunction to those with preoperative renal dysfunction. METHODS: Data was prospectively collected on 19,625 consecutive patients undergoing isolated coronary surgery between 1997 and 2003 from four institutions. Sixty-seven patients had a history of dialysis support prior to coronary surgery, and were excluded from the main analysis of the study. The remaining 19,558 patients were divided into two groups based on preoperative serum creatinine level, patients with preoperative renal dysfunction with serum creatinine levels >200 micromol/L without dialysis support and control patients with preoperative serum creatinine levels <200 micromol/L. Case-mix was accounted for by developing a propensity score, which was the probability of belonging to the non-dialysis-dependent renal dysfunction group, and included in the multivariable analyses. RESULTS: There were 19,172 patients with preoperative serum creatinine levels <200 micromol/L and 386 patients with serum creatinine levels >200 micromol/L without dialysis support. The propensity score included sex, body mass index, co-morbidity factors (respiratory disease, diabetes, cerebrovascular disease, hypertension, and hypercholesterolemia), ejection fraction, left main stem stenosis, emergency status, prior cardiac surgery, off-pump surgery, and the logistic EuroSCORE. After adjusting for the propensity score, patients with preoperative non-dialysis-dependent renal dysfunction had significantly higher in-hospital mortality (adjusted odds ratio 3.0, p < 0.001), stroke (adjusted odds ratio 2.0, p = 0.033), atrial arrhythmia (adjusted odds ratio 1.5, p = 0.003), prolonged ventilation (adjusted odds ratio 2.1, p < 0.001), and post-op stay > 6 days (adjusted odds ratio 2.6, p < 0.001). One thousand one hundred and eighty-three (6.1%) deaths occurred during 58,062 patient-years follow-up. After adjusting for the propensity score, the adjusted hazard ratio of mid-term mortality for non-dialysis-dependent renal dysfunction was 2.7 (p < 0.001). CONCLUSIONS: Patients undergoing coronary surgery with non-dialysis-dependent renal dysfunction have significantly increased perioperative morbidity and mortality. Mid-term survival is also significantly reduced at 5-years.

Aged↗

PubMed2003

Gender and outcomes after coronary artery bypass grafting: a propensity-matched comparison.

OBJECTIVE: Our objective is to determine whether gender is a marker or a causal influence for poor outcomes after coronary revascularization. METHODS: Propensity-modeling techniques were used to investigate whether gender adversely impacts outcomes after coronary revascularization. A parsimonious explanatory model was developed by bootstrap bagging with variable selection from 64 baseline and 37 operative variables. Propensity scores were calculated from a logistic model that included the parsimonious model and additional baseline variables. Greedy matching techniques were applied to match female and male patients to the nearest propensity scores. Comparisons were made among the propensity-matched women and men. RESULTS: Of the 15,597 patients undergoing isolated coronary artery bypass graft surgery, only 26% of the 3596 women were matched on propensity scores with men. Distribution of covariates among the matched pairs was, on average, equal. Postoperative mortality (P =.76), neurologic morbidity (global deficit P =.07, focal deficit P =.51), infection (sepsis P =.88), mediastinitis (P =.18), renal failure (P =.84), intra-aortic balloon pump usage (P =.61), and reoperation for bleeding (P =.10) were similar among women and men. Occurrence of Q-wave myocardial infarction (P = <.01), postoperative inotropic usage (P = <.01), and prolonged ventilatory support (P =.02) were more common in women compared with propensity-matched men. CONCLUSIONS: The preoperative profiles of women and men are markedly different. Propensity matching women and men was difficult, because only 26% of women were able to be matched with men. However, in well-matched patients, female gender was not associated with increased mortality and had minimal impact on morbidity after coronary artery bypass grafting.

Aged↗

PubMed2006

Comparing the long-term clinical outcome of treatment with methotrexate or sulfasalazine prescribed as the first disease-modifying antirheumatic drug in patients with inflammatory polyarthritis.

OBJECTIVE: To compare the clinical and functional outcome at 2 and 5 years in patients with inflammatory polyarthritis treated with either methotrexate (MTX) or sulfasalazine (SSZ) as the first disease-modifying antirheumatic drug (DMARD). METHODS: Patients recruited to a primary-care-based inception cohort of patients with inflammatory polyarthritis were eligible for this analysis if they were started on either SSZ (n = 331) or MTX (n = 108) as their first DMARD within 3 months. Outcomes assessed included the Disease Activity Score (DAS)28, Health Assessment Questionnaire, radiological erosions (Larsen Score) and cumulative mortality with the proportions still on the original treatment. To overcome potential bias in allocation to these two treatments, a propensity score was calculated based on baseline disease status variables. RESULTS: are expressed as the mean difference between MTX and SSZ, both unadjusted and adjusted for propensity score. RESULTS: The baseline differences between the two groups disappeared after adjusting for propensity score. At 2 and 5 years there were few differences in the clinical outcomes, either unadjusted or after adjustment for propensity. By contrast, at 5 years the proportion that was erosive was lower in the MTX group: odds ratio 0.3 (95% confidence interval 0.1 to 0.8), with a 31% lower Larsen Score after adjustment. At both time points, those treated with MTX were at least twice as likely to remain on that drug as those treated with SSZ. CONCLUSION: Long-term clinical outcome is similar in patients prescribed MTX and SSZ, although it would seem that MTX has greater potential to suppress erosions, which supports it being the first DMARD of choice.

Adult↗

PubMed2006

The impact of gender on in-hospital mortality and morbidity after isolated aortic valve replacement.

The objective of our retrospective investigation was to examine the influence of gender on in-hospital mortality and morbidity after isolated aortic valve replacement (AVR). Between January 1993 and June 2002, 2212 patients (782 females, 1430 males) underwent AVR. Propensity matching was used to adjust for numerous differences in baseline characteristics and perioperative variables between groups. Unadjusted in-hospital mortality was higher in females (27 [3.5%] females versus 23 [1.6%] males; P = 0.005). An analysis using 1:1 matching by propensity score did not find a significant difference in in-hospital mortality [OR (95% confidence intervals), 1.0 [0.4, 2.6]; P = 0.99) or overall morbidity (1.4 [0.7, 2.5]; P = 0.29) between groups. Further analyses, including classification of women and men into quintile groups by propensity scores and logistic regression models with propensity score adjustment, found that females were at increased risk for cardiac morbidity [OR (95% CI), 3.4 [1.1, 10.8]; P = 0.038), but not mortality (0.9 [0.3, 2.5]; P = 0.88) nor other morbidities. These results suggest that there is no greater than a 2.5-fold increase in risk for females compared with males undergoing AVR. Female gender, however, may impart increased risk for cardiac morbidity after AVR.

Aged↗

PubMed2004

"Renalism": inappropriately low rates of coronary angiography in elderly individuals with renal insufficiency.

Higher risk patients (including the elderly) receive more conservative therapy for cardiovascular diseases, even though the relative benefits of therapy tend to be greater. The perceived risk of radiocontrast-associated nephrotoxicity may influence the provision of coronary angiography and subsequent revascularization, especially among individuals with chronic kidney disease (CKD). The aim of this study was to determine whether there is excessive variation in the provision of coronary angiography after acute myocardial infarction on the basis of the presence of CKD and whether there is an association between angiography and mortality. Elderly (age 65 to 89 yr) individuals with acute myocardial infarction from the Cooperative Cardiovascular Project were classified by the presence or absence of CKD (defined as a baseline serum creatinine of 1.5 to 5.0 mg/dl). In CKD patients, the propensity to undergo coronary angiography was determined and the effect of coronary angiography on mortality was estimated using multivariable logistic regression and stratification. Mortality was significantly higher with CKD (52.6 versus 26.4%). Fewer patients with CKD underwent coronary angiography (25.2 versus 46.8%) despite the observation that a similar proportion of patients were deemed appropriate for angiography by standard, published criteria. When limiting the analysis to CKD patients who are considered appropriate, the multivariable estimate of the odds of death associated with coronary angiography was 0.58 (95% confidence interval, 0.50 to 0.67). With adjustment using propensity scores, the odds ratio averaged across propensity score quintiles was 0.62 (95% confidence interval, 0.54 to 0.70). Results were qualitatively similar when patients were stratified by CKD stage IV (estimated GFR <30 ml/min per 1.73 m(2)). There is a large relative decrease in utilization of coronary angiography among patients with CKD. Alteration in practice because of an aversion to the risk of radiocontrast-associated nephrotoxicity ("renalism") is inappropriate, even if the true relative benefit of invasive strategies is a fraction of what is estimated here.

Age Factors↗

PubMedDate not supplied

Cost and utilization comparisons among propensity score-matched insulin lispro and regular insulin users.

OBJECTIVE: To compare cost and utilization among users of insulin lispro and regular (human) insulin. METHODS: This was a retrospective analysis using administrative claims data for continuously enrolled subjects using insulin lispro or regular insulin between January 1, 1998, and December 21, 1999. Subjects were matched 1 to 1 on the propensity to receive lispro versus regular insulin using a score estimated from baseline characteristics such as age, gender, comorbidities, and oral hypoglycemic use. Once matched, 12 months of follow-up pharmacy and medical cost and utilization data (e.g. prescriptions, office visits, hospitalizations) from July 1,1997, through December 31, 2000, were analyzed using univariate statistics. RESULTS: Of 11,443 subjects, 3,341 (29.2%) had received a prescription for insulin lispro, while 8,102 (70.8%) had received a prescription for regular insulin. At baseline, lispro subjects tended to be younger, more often had type 1 diabetes and a history of insulin use, had fewer comorbidities, visited endocrinologists more often than family practice physicians, and had lower total costs. After matching on propensity score to within +/-0.01, 1,832 subject pairs were retained. On average, lispro subjects had significantly more office visits (P=0.0022) and pharmacy prescriptions (P=0.0165) but fewer inpatient hospital visits (P=0.0028)compared to regular insulin subjects. Cost results were similar, with insulin lispro subjects having significantly higher average office visit costs (P=0.0237) and pharmacy costs (P<0.0001) but lower inpatient hospital costs (P=0.0227). Total costs were not significantly different between treatment groups (P=0.5266). CONCLUSION: Total direct health care costs were not different between insulin lispro and regular insulin users. An association was observed between higher direct drug product cost and more intensive ambulatory care for insulin lispro users and lower inpatient hospital cost in the short-term.

Administration, Oral↗

PubMed2005

Equivalence of mail and telephone responses to the CAHPS Hospital Survey.

OBJECTIVE: To estimate the effect of survey mode (mail versus telephone) on reports and ratings of hospital care. DATA SOURCES/STUDY SETTING: The total sample included 20,826 patients discharged from a group of 24 distinct hospitals in three states (Arizona, Maryland, New York). We collected CAHPS data in 2003 by mail and telephone from 9,504 patients, of whom 39 percent responded by telephone and 61 percent by mail. STUDY DESIGN: We estimated mode effects in an observational design, using both propensity score blocking and (ordered) logistic regression on covariates. We used variables derived from administrative data (either included as covariates in the regression function or used in estimating the propensity score) grouped in three categories: individual characteristics, characteristics of the stay and hospital, and survey administration variables. DATA COLLECTION/EXTRACTION METHODS: We mailed a 66-item questionnaire to everyone in the sample and followed up by telephone with those who did not respond. PRINCIPAL FINDINGS: We found significant (p<.01) mode effects for 13 of the 21 questions examined in this study. The maximum magnitude of the survey mode effect was an 11 percentage-point difference in the probability of a "yes" response to one of the survey questions. Telephone respondents were more likely to rate care positively and health status negatively, compared with mail respondents. Standard regression-based case-mix adjustment captured much of the mode effects detected by propensity score techniques in this application. CONCLUSIONS: Telephone mode increases the propensity for more favorable evaluations of care for more than half of the items examined. This suggests that mode of administration should be standardized or carefully adjusted for. Alternatively, further item development may minimize the sensitivity of items to mode of data collection.

Data Collection↗

PubMed2000

Prophylactic value of preincision intra-aortic balloon pump: analysis of a statewide experience.

OBJECTIVE: The objective of this study was to determine whether preincision use of an intra-aortic balloon pump improves survival and shortens postoperative length of stay in hemodynamically stable, high-risk patients undergoing coronary artery bypass grafting. METHODS: A post hoc analysis of the Alabama CABG Cooperative Project database was performed by using propensity scores to model the likelihood of receiving a prophylactic preincision intra-aortic balloon pump. Every patient receiving a prophylactic preincision balloon pump was matched with another patient of similar propensity score who did not receive one. We then compared outcomes for matched pairs. RESULTS: There were 7581 patients of whom 592 received a prophylactic preincision balloon pump. Patients with preoperative renal insufficiency, heart failure, or left main coronary artery disease, or who had undergone previous bypass grafting were significantly more likely to receive a prophylactic preincision balloon pump. By using propensity scores, we matched 550 patients who received a prophylactic preincision balloon pump with 550 who did not. Survival did not significantly differ by whether a prophylactic preincision balloon pump was used. However, surviving patients who received a preincision balloon pump had a significantly shorter postbypass length of stay (7 +/- 7.3 days) than did matched patients not receiving a balloon pump (8 +/- 6.2 days; P <.05). CONCLUSIONS: No survival advantage was found for use of a prophylactic intra-aortic balloon pump in hemodynamically stable, high-risk patients undergoing bypass grafting, as opposed to placing a balloon pump on an "as needed" basis during or after the operation. However, the patients receiving the balloon pump had improved convalescence as shown by significantly shorter length of stay.

Aged↗

PubMed1996

Sources of selection bias in evaluating social programs: an interpretation of conventional measures and evidence on the effectiveness of matching as a program evaluation method.

This paper decomposes the conventional measure of selection bias in observational studies into three components. The first two components are due to differences in the distributions of characteristics between participant and nonparticipant (comparison) group members: the first arises from differences in the supports, and the second from differences in densities over the region of common support. The third component arises from selection bias precisely defined. Using data from a recent social experiment, we find that the component due to selection bias, precisely defined, is smaller than the first two components. However, selection bias still represents a substantial fraction of the experimental impact estimate. The empirical performance of matching methods of program evaluation is also examined. We find that matching based on the propensity score eliminates some but not all of the measured selection bias, with the remaining bias still a substantial fraction of the estimated impact. We find that the support of the distribution of propensity scores for the comparison group is typically only a small portion of the support for the participant group. For values outside the common support, it is impossible to reliably estimate the effect of program participation using matching methods. If the impact of participation depends on the propensity score, as we find in our data, the failure of the common support condition severely limits matching compared with random assignment as an evaluation estimator.

Bias↗

PubMed2005

Coronary revascularization without cardiopulmonary bypass versus the conventional approach in high-risk patients.

BACKGROUND: The premise of coronary revascularization without cardiopulmonary bypass (off-pump coronary artery bypass graft [CABG]) proposes that patient morbidity and, potentially, mortality can be reduced without compromising the excellent results of conventional revascularization techniques (on-pump CABG). High-risk patients may benefit the most from off-pump CABG. The aim of this study was to compare early and mid-term clinical outcomes after off-pump CABG with on-pump CABG in a subset of high-risk patients. METHODS: Between January 1, 2000 and December 31, 2000, 513 high-risk patients with a Parsonnet's risk scores of 20 or higher underwent CABG; 38.6% (n = 198) underwent on-pump CABG, and 61.4% (n = 315) had off-pump CABG. Logistic regression was used to calculate the probability of being selected for on-pump CABG given a set of preoperative risk factors. Propensity scores or the probability of being selected for on-pump CABG were computed. Relative risks, heterogeneity among strata, and interactions between surgery type and the propensity score were assessed by a multivariate Cox proportional-hazards regression for the outcomes mortality and major adverse cardiac events (death, acute myocardial infarction, stroke, reoperative CABG, percutaneous coronary intervention). RESULTS: Operative mortality was lower after off-pump versus on-pump CABG between the two groups after controlling for preoperative risk factors using the propensity score (odds ratio = 2.10; 95% confidence intervals = 1.02 to 4.36, p = 0.04). In the Cox-regression analysis, off-pump CABG was associated with an improved survival rate compared with on-pump CABG (p = 0.03). Off-pump CABG was associated with a comparable event-free survival (p = 0.14) compared with on-pump CABG. CONCLUSIONS: Off-pump CABG can be performed with a reasonably low morbidity and lower early and late mortality in high-risk patients. Off-pump CABG may be a better operative strategy in this subset of patients.

Aged↗

PubMed2005

On the use of discrete choice models for causal inference.

Methodology for causal inference based on propensity scores has been developed and popularized in the last two decades. However, the majority of the methodology has concentrated on binary treatments. Only recently have these methods been extended to settings with multi-valued treatments. We propose a number of discrete choice models for estimating the propensity scores. The models differ in terms of flexibility with respect to potential correlation between treatments, and, in turn, the accuracy of the estimated propensity scores. We present the effects of discrete choice models used on performance of the causal estimators through a Monte Carlo study. We also illustrate the use of discrete choice models to estimate the effect of antipsychotic drug use on the risk of diabetes in a cohort of adults with schizophrenia.

Adolescent↗

PubMed2006

Patterns of asthma-related health care resource use in children treated with montelukast or fluticasone.

OBJECTIVE: To examine the impact of controller monotherapy with montelukast or fluticasone on asthma-related health care resource use among children aged 2-14 years old. DESIGN AND METHODS: A retrospective claims-based analysis of asthmatic children, 2-14 years old, receiving a prescription (index) for montelukast or fluticasone between January 1, 1999 and June 30, 2000 was conducted. Children were matched by age and propensity score to obtain comparable treatment groups. The propensity score was derived using patient demographics, pre-existing respiratory conditions, and asthma-related pharmacy and health service utilization (i.e. ambulatory visits, emergency department visits and hospitalizations). Claims for asthma-related emergent care and medication use were examined for the 12-month periods before and after the index prescription. Treatment group comparisons of asthma-related resource use were conducted for the total pediatric population and separately for children 2-5 years and 6-14 years. Persistent controller medication use was assessed at 6 and 12 months post-index. RESULTS: A total of 2034 children were matched (1017 in each treatment group). Post-index rates of asthma-related resource use were similar among children treated with montelukast or fluticasone. Among children 2-5 years old, fewer emergency department visits were observed with montelukast versus fluticasone (relative risk = 0.52, 95% confidence interval [CI]: 0.28-0.96); no significant difference was observed among children 6-14 years old. No significant differences between montelukast and fluticasone cohorts in hospitalizations or rescue medication fills were noted in either age group. Evidence of at least one medication refill was significantly greater with montelukast at both 6 and 12 months post-index. CONCLUSIONS: Similar levels of resource use were achieved by children 2-14 years initiating montelukast or fluticasone, as indicated by use of asthma-related emergent care and rescue/acute medications. Subgroup analyses suggest a differential effect of age on the relationship between treatment and asthma-related resource use, with children 2-5 years observed to have less resource use while on montelukast.

Acetates↗

PubMed2006

Predicting therapeutic benefit from myocardial revascularization procedures: are measurements of both resting left ventricular ejection fraction and stress-induced myocardial ischemia necessary?

BACKGROUND: We hypothesized that ejection fraction (EF) best predicts cardiovascular death but only measures of ischemia predict relative survival benefit from revascularization compared with medical therapy. METHODS AND RESULTS: We followed up 5366 consecutive patients without prior revascularization who underwent stress electrocardiography-gated myocardial perfusion single photon emission computed tomography (MPS) for 2.8 +/- 1.2 years, during which 146 cardiac deaths occurred (2.7%, 1.0%/y). The treatment received within 60 days after MPS was used to define the subgroups (revascularization in 402 patients, with cardiac death occurring in 6.2%, vs medical therapy in 4964 patients, with cardiac death occurring in 2.4%; P < .0001, chi2 = 18.7). Adjustment for nonrandomized treatment assignment used a propensity score based on logistic regression modeling of referral to revascularization. The percent of myocardium that was ischemic was the most important predictor of revascularization. The overall model (multivariate chi2 = 728, c index = 0.89, P < 10(-5)) was used as a propensity score. Cox proportional hazards analysis, assessing the relationship between MPS results, non-MPS covariates, and cardiac death, revealed that EF was superior to percent ischemic myocardium in the prediction of cardiac death after adjustment for pre-MPS data and the propensity score. However, an interaction between percent ischemic myocardium and revascularization was present such that, irrespective of EF, patients with little or no ischemia had an improved survival rate with medical therapy, whereas with increasing ischemia, progressive improvements in survival rate were noted with revascularization. CONCLUSIONS: Although EF predicts cardiac death, only inducible ischemia identifies which patients have a short-term benefit from revascularization.

Coronary Artery Disease↗