To the Editor: Dr Peterson and colleagues1 evaluated the association between adherence to 9 American College of Cardiology/American Heart Association (ACC/AHA) class I guideline-recommended treatments and risk-adjusted in-hospital mortality. The study population included those patients with non–ST-segment elevation acute coronary syndrome in the CRUSADE (Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes With Early Implementation of the ACC/AHA Guidelines) registry—a voluntary, self-reported, observational registry. The primary finding was that risk-adjusted in-hospital mortality was 6.31% for the lowest adherence quartile compared with 4.15% for the highest adherence quartile (P<.001). Observational registries are extremely useful for studying large populations or rare conditions. However, they are intrinsically limited by potential selection and reporting bias, confounders, and nonvalidated data, and hence best suited for generating hypotheses rather than proving causality.
One important potential confounder was the exclusion of 9155 patients (11.8% of the cohort) who were transferred from a participating hospital; this was performed because the longitudinal end point assessment was not possible. We are interested in the clinical characteristics and treatment adherence for this patient subgroup at the time of transfer from the first hospital. Was this subgroup sicker or healthier than the rest of the cohort, and what was the adherence to treatment at the time of transfer? What effect would there be on the results if in-hospital mortality was determined, or if the patient was censored at time of transfer? Simply excluding this cohort may lead to selection bias, since the remaining patients who are not transferred may be sicker, may not be eligible for an invasive approach, and may exhibit higher in-hospital mortality. When the analysis was limited to hospitals performing coronary artery bypass graft surgery, the absolute difference for in-hospital mortality was much smaller (4.36% vs 3.67%).
The authors also discussed that adherence to these 9 treatments may be surrogate markers for quality rather than represent direct causal agents.2 - 4 This is an important point because 5 of the 9 guideline-recommended treatments were prescriptions of discharge medications and would not be causally related to in-hospital mortality. We are therefore interested in the effect on in-hospital mortality if the analysis were limited to adherence to the 4 acute medications (aspirin, β-blocker, heparin, and glycoprotein IIb/IIIa inhibitors) used within the first 24 hours.
Financial Disclosures: None reported.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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