Troponin T monitoring to detect myocardial injury after noncardiac surgery: a cost-consequence analysis.

BACKGROUND: Myocardial injury after noncardiac surgery (MINS) is a mostly asymptomatic condition that is strongly associated with 30-day mortality; however, it remains mostly undetected without systematic troponin T monitoring. We evaluated the cost and consequences of postoperative troponin T monitoring to detect MINS. METHODS: We conducted a model-based cost-consequence analysis to compare the impact of routine troponin T monitoring versus standard care (troponin T measurement triggered by ischemic symptoms) on the incidence of MINS detection. Model inputs were based on Canadian patients enrolled in the Vascular Events in Noncardiac Surgery Patients Cohort Evaluation (VISION) study, which enrolled patients aged 45 years or older undergoing inpatient noncardiac surgery. We conducted probability analyses with 10 000 iterations and extensive sensitivity analyses. RESULTS: The data were based on 6021 patients (48% men, mean age 65 [standard deviation 12] yr). The 30-day mortality rate for MINS was 9.6%. We determined the incremental cost to avoid missing a MINS event as $1632 (2015 Canadian dollars). The cost-effectiveness of troponin monitoring was higher in patient subgroups at higher risk for MINS, e.g., those aged 65 years or more, or with a history of atherosclerosis or diabetes ($1309). CONCLUSION: The costs associated with a troponin T monitoring program to detect MINS were moderate. Based on the estimated incremental cost per health gain, implementation of postoperative troponin T monitoring seems appealing, particularly in patients at high risk for MINS.

CONTEXTE: Les lésions myocardiques après chirurgie non cardiaque (CNC) sont majoritairement asymptomatiques et fortement associées au risque de mortalité dans les 30 jours; toutefois, dans la plupart des cas, elles ne sont pas détectées en l'absence d'une surveillance systématique de la troponine T. Nous avons évalué les coûts et les conséquences d'une telle surveillance pour détecter les lésions myocardiques après CNC. MÉTHODES: Nous avons mené une analyse coût-conséquence modélisée pour comparer la surveillance systématique de la troponine T aux soins habituels seuls (mesure de la troponine T seulement s'il y a présence de symptômes d'ischémie) sur la fréquence de détection de lésions myocardiques après CNC. Les données ayant servi à l'analyse provenaient des patients canadiens ayant participé à l'étude de cohorte VISION, qui visait à évaluer les complications vasculaires chez les patients de 45 ans et plus ayant subi une CNC. Nous avons mené des analyses de probabilité avec 10  000 itérations et des analyses de sensibilité approfondies. RÉSULTATS: Les données portaient sur 6021 patients (48 % du sexe masculin; âge moyen de 65 ans [écart-type de 12 ans]). Le taux de mortalité dans les 30 jours associé à une lésion myocardique après CNC était de 9,6 %. Nous avons déterminé que le coût marginal de la détection de la présence d'une lésion par surveillance de la troponine T était de 1632 $ (dollars canadiens en 2015). Le rapport coût-efficacité était plus bas pour les sous-groupes de patients à risque élevé de lésion myocardique après CNC, comme les patients de 65 ans et plus ou ceux ayant des antécédents d'athérosclérose ou de diabète (1309 $), que pour leurs pairs. CONCLUSION: Les coûts associés à un programme de surveillance de la troponine T pour détecter les lésions myocardiques après CNC étaient modérés. Le coût marginal estimé par gain de santé indique que la mise en œuvre de ce type de programme pourrait être une option intéressante, surtout pour les patients à risque élevé de lésion myocardique après CNC.

Comparison of the ability of double-robust estimators to correct bias in propensity score matching analysis. A Monte Carlo simulation study.

OBJECTIVE: As covariates are not always adequately balanced after propensity score matching and double- adjustment can be used to remove residual confounding, we compared the performance of several double-robust estimators in different scenarios. METHODS: We conducted a series of Monte Carlo simulations on virtual observational studies. After estimating the propensity scores by logistic regression, we performed 1:1 optimal, nearest-neighbor, and caliper matching. We used 4 estimators on each matched sample: (1) a crude estimator without double-adjustment, (2) double-adjustment for the propensity scores, (3) double-adjustment for the unweighted unbalanced covariates, and (4) double-adjustment for the unbalanced covariates, weighted by their strength of association with the outcome. RESULTS: The crude estimator led to highest bias in all tested scenarios. Double-adjustment for the propensity scores effectively removed confounding only when the propensity score models were correctly specified. Double-adjustment for the unbalanced covariates was more robust to misspecification. Double-adjustment for the weighted unbalanced covariates outperformed the other approaches in every scenario and using any matching algorithm, as measured by the mean squared error. CONCLUSION: Double-adjustment can be used to remove residual confounding after propensity score matching. The unbalanced covariates with the strongest confounding effects should be adjusted.

Magnitude and direction of missing confounders had different consequences on treatment effect estimation in propensity score analysis.

OBJECTIVE: Propensity score (PS) analysis allows an unbiased estimate of treatment effects but assumes that all confounders are measured. We assessed the impact of omitting confounders from a PS analysis on clinical decision making. STUDY DESIGN AND SETTING: We conducted Monte Carlo simulations on hypothetical observational studies based on virtual populations and on the population from a large randomized trial (CRASH-2). In both series of simulations, PS analysis was conducted with all confounders and with omitted confounders, which were defined to have different strengths of association with the outcome and treatment exposure. After inverse probability of treatment weighting, we calculated the absolute risk differences and numbers needed to treat (NNT). RESULTS: In both series of simulations, omitting a confounder that was moderately associated with the outcome and exposure led to negligible bias on the NNT scale. The bias induced by omitting strongly positive confounding variables remained less than 15 patients to treat. Major bias and reversed effects were found only when omitting highly prevalent, strongly negative confounders that were similarly associated with the outcome and exposure with odds ratios greater than 4.00 (or <0.25). This omission was accompanied by a substantial decrease in analysis power. CONCLUSION: The omission of strongly negative confounding variables from a PS analysis can lead to incorrect clinical decision making. However, omitting these variables also decreases the analysis power, which may prevent the reporting of significant but misleading effects.

Rationale and design of the coronary artery bypass grafting surgery off or on pump revascularization study: a large international randomized trial in cardiac surgery.

BACKGROUND: Uncertainty remains regarding the benefits and risks of the technique of operating on a beating heart (off pump) for coronary artery bypass grafting (CABG) surgery versus on-pump CABG. Prior trials had few events and relatively short follow-up. There is a need for a large randomized, controlled trial with long-term follow-up to inform both the short- and long-term impact of the 2 approaches to CABG. METHODS: We plan to randomize 4,700 patients in whom CABG is planned to undergo the procedure on pump or off pump. The coprimary outcomes are a composite of total mortality, myocardial infarction (MI), stroke, and renal failure at 30 days and a composite of total mortality, MI, stroke, renal failure, and repeat revascularization at 5 years. We will also undertake a cost-effectiveness analysis at 30 days and 5 years after CABG surgery. Other outcomes include neurocognitive dysfunction, recurrence of angina, cardiovascular mortality, blood transfusions, and quality of life. RESULTS: As of May 3, 2011, CORONARY has recruited >3,884 patients from 79 centers in 19 countries. Currently, patient's mean age is 67.6 years, 80.7% are men, 47.0% have a history of diabetes, 51.4% have a history of smoking, and 34.4% had a previous MI. In addition, 20.9% of patients have a left main disease, and 96.6% have double or triple vessel disease. CONCLUSIONS: CORONARY is the largest trial yet conducted comparing off-pump CABG to on-pump CABG. Its results will lead to a better understanding of the safety and efficacy of off-pump CABG.