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Background Jehovah's Witness patients (Witnesses) who undergo cardiac surgery provide a unique natural experiment in severe blood conservation because anemia, transfusion, erythropoietin, and antifibrinolytics have attendant risks. Our objective was to compare morbidity and long-term survival of Witnesses undergoing cardiac surgery with a similarly matched group of patients who received transfusions. Methods A total of 322 Witnesses and 87 453 non-Witnesses underwent cardiac surgery at our center from January 1, 1983, to January 1, 2011. All Witnesses prospectively refused blood transfusions. Among non-Witnesses, 38 467 did not receive blood transfusions and 48 986 did. We used propensity methods to match patient groups and parametric multiphase hazard methods to assess long-term survival. Our main outcome measures were postoperative morbidity complications, in-hospital mortality, and long-term survival. Results Witnesses had fewer acute complications and shorter length of stay than matched patients who received transfusions: myocardial infarction, 0.31% vs 2.8% (P = . 01); additional operation for bleeding, 3.7% vs 7.1% (P = . 03); prolonged ventilation, 6% vs 16% (P Conclusions Witnesses do not appear to be at increased risk for surgical complications or long-term mortality when comparisons are properly made by transfusion status. Thus, current extreme blood management strategies do not appear to place patients at heightened risk for reduced long-term survival.

Little is known about the association between exercise capacity and nonfatal cardiac events in patients referred for exercise treadmill testing (ETT). Our objective was to determine the prognostic importance of exercise capacity for nonfatal cardiac events in a clinical population.A cohort study was performed of 9191 patients referred for ETT. Median follow-up was 2.7 years. Exercise capacity was quantified as the proportion of age- and sex-predicted metabolic equivalents achieved and categorized as less than 85%, 85% to 100%, and greater than 100%. Individual primary outcomes were myocardial infarction, unstable angina, and coronary revascularization. All-cause mortality was a secondary outcome.Patients with lower exercise capacity were more likely to be female (55.38% vs 42.62%); to have comorbidities such as diabetes (23.16% vs 9.61%) and hypertension (59.43% vs 44.05%); and to have abnormal ETT findings such as chest pain on the treadmill (12.09% vs 7.63%), abnormal heart rate recovery (82.74% vs 64.13%), and abnormal chronotropic index (32.89% vs 12.20%). In multivariable analysis, including other ETT variables, lower exercise capacity (85% of predicted) was associated with increased risk of myocardial infarction (hazard ratio [HR], 2.36; 95% confidence interval [CI], 1.55-3.60), unstable angina (HR, 2.39; 95% CI, 1.78-3.21), coronary revascularization (HR, 1.75; 95% CI, 1.46- 2.08), and all-cause mortality (HR, 2.90; 95% CI, 1.88-4.47) compared with exercise capacity greater than 100% of predicted.Adjusting for patient characteristics and other ETT variables, reduced exercise capacity was associated with both nonfatal cardiovascular events and mortality in patients referred for ETT.

Verification bias occurs when test findings influence the decision to perform a gold standard test. It adversely influences diagnostic test accuracy by inflating sensitivity and deflating specificity. We studied the impact of verification bias on the estimated accuracy of a test commonly used in suspected lung cancer.We studied 534 consecutive patients referred for [(18)F]fluorodeoxyglucose uptake by positron emission tomography (PET). Primary outcomes were tissue diagnoses of cancer and of mediastinal lymph node metastases. A secondary outcome was 3-year mortality. We accounted for verification bias using 2 validated methods.The gold standard test, namely tissue acquisition, was performed in 419 patients (78%); mediastinal lymph node sampling occurred in 301 (56%). While the 410 patients with PET-diagnosed stage I cancer or higher were more likely than patients with negative PET scan findings to undergo tissue diagnosis testing (92% vs 34%) (P.001), there was no association between PET findings and performance of mediastinal sampling. Without accounting for verification bias, the sensitivity and specificity of PET for diagnosis of cancer were 0.95 (95% confidence interval [CI], 0.92-0.97) and 0.31 (95% CI, 0.21-0.42), respectively. After adjustment, sensitivity fell to 0.85 (95% CI, 0.81-0.89), while specificity increased to 0.51 (95% CI, 0.40-0.60). For diagnosis of mediastinal disease, verification bias had slight effects on test accuracy. There were 224 deaths, with a strong gradient between PET stage and death (P.001).The diagnostic accuracy of PET for assessment of suspected lung cancer is substantially affected by verification bias.

More than 1100 articles now appear annually investigating "independent risk factors" or "independent predictors" for various clinical outcomes. In medical research, independence is generally defined in a statistical sense: a variable is called an independent risk factor if it has a significant contribution to an outcome in a statistical model that includes established risk factors. As such, independence is based on a specific statistical model and depends on the set of established risk factors included in that model. Even when strong statistical evidence indicates that a variable is an independent risk factor for an outcome, this does not necessarily indicate that the risk factor causally contributes to the outcome. The opposite is also true: risk factors that have causal relationships with the outcome will not necessarily prove to be independent risk factors. These are basic statistical principles that are too often given short shrift in medical research. Herein, we discuss the clinical implications conferred by the above definition of independence, primarily using examples from recent cardiovascular literature. A glossary and schema are provided to help clinicians and researchers understand and discuss these matters effectively.

Despite multiple randomized trials demonstrating their efficacy for the secondary prevention of coronary disease, lipid-lowering agents remain underused. Few studies have examined the relationship between predischarge initiation of lipid-lowering therapy and long-term use.Using data from patients at 69 centers from the United States and Canada enrolled in the Evaluation in PTCA to Improve Long-term Outcome With Abciximab GP IIb/IIIa Blockade (EPILOG) trial, we performed a retrospective propensity-analyzed cohort study. Patients underwent percutaneous coronary intervention for stable or recently unstable coronary disease and were older than 21 years, were not taking lipid-lowering therapy at the time of admission, and survived to hospital discharge; 175 were discharged taking lipid-lowering therapy and 1951 were not.After 6 months, 77% of patients who started taking lipid-lowering agents before hospital discharge continued taking therapy, compared with only 25% of those discharged without these agents (relative risk, 3.17; 95% confidence interval, 2.88-3.41; P.001). After restricting the analysis to propensity-matched patients (n = 477) and adjusting for other potential confounders, initiation of a lipid-lowering agent during hospitalization was the strongest independent predictor of use at 6 months (relative risk, 2.50; 95% confidence interval, 2.29-2.65; P.001).Inpatient initiation of lipid-lowering therapy is a strong and independent positive predictor of subsequent use, with patients who start taking lipid-lowering therapy before hospital discharge nearly 3 times as likely to be taking these agents 6 months later. Inpatient initiation of lipid-lowering therapy appears to be an effective strategy for bridging the gap between current medical knowledge and practice.