Regression spline bivariate probit models: A practical approach to testing for exogeneity

Bivariate probit models can deal with a problem usually known as endogeneity. This issue is likely to arise in observational studies when confounders are unobserved. We are concerned with testing the hypothesis of exogeneity (or absence of endogeneity) when using regression spline recursive and sample selection bivariate probit models. Likelihood ratio and gradient tests are discussed in this context and their empirical properties investigated and compared with those of the Lagrange multiplier and Wald tests through a Monte Carlo study. The tests are illustrated using two datasets in which the hypothesis of exogeneity needs to be tested

Does hospital admission/observation for chest pain improve patient outcomes after emergency department evaluation for suspected acute coronary syndrome?

Background Chest pain is the top reason for hospitalization/observation in the USA, but it is unclear if this strategy improves patient outcomes. Objective The objective of this study was to compare 30-day outcomes for patients admitted versus discharged after a negative emergency department (ED) evaluation for suspected acute coronary syndrome. Design A retrospective, multi-site, cohort study of adult encounters with chest pain presenting to one of 13 Kaiser Permanente Southern California EDs between January 1, 2015, and December 1, 2017. Instrumental variable analysis was used to mitigate potential confounding by unobserved factors. Patients All adult patients presenting to an ED with chest pain, in whom an acute myocardial infarction was not diagnosed in the ED, were included. Main Measures The primary outcome was 30-day acute myocardial infarction or all-cause mortality, and secondary outcomes included 30-day revascularization and major adverse cardiac events. Key Results In total, 77,652 patient encounters were included in the study (n=11,026 admitted, 14.2%). Three hundred twenty-two (0.4%) had an acute myocardial infarction (n=193, 0.2%) or death (n=137, 0.2%) within 30 days of ED visit (1.5% hospitalized versus 0.2% discharged). Very few (0.3%) patients underwent coronary revascularization within 30 days (0.7% hospitalized versus 0.2% discharged). Instrumental variable analysis found no adjusted differences in 30-day patient outcomes between the hospitalized cohort and those discharged (risk reduction 0.002, 95% CI −0.002 to 0.007). Similarly, there were no differences in coronary revascularization (risk reduction 0.003, 95% CI −0.002 to 0.007). Conclusion Among ED patients with chest pain not diagnosed with an acute myocardial infarction, risk of major adverse cardiac events is quite low, and there does not appear to be any benefit in 30-day outcomes for those admitted or observed in the hospital compared to those discharged with outpatient follow-up

Early noninvasive cardiac testing after emergency department evaluation for suspected acute coronary syndrome

Importance Professional guidelines recommend noninvasive cardiac testing (NIT) within 72 hours of an emergency department (ED) evaluation for suspected acute coronary syndrome. However, there is inexact evidence that this strategy reduces the risk of future death or acute myocardial infarction (MI). Objective To evaluate the effectiveness of early NIT in reducing the risk of death or acute MI within 30 days. Design, Setting, and Participants This retrospective, multicenter cohort study within the Kaiser Permanente Southern California integrated health care delivery system compared the effectiveness of early noninvasive cardiac testing vs no testing in patients with chest pain and in whom acute MI was ruled out who presented to an ED from January 2015 to December 2017. Patients were followed up for up to 30 days after emergency department discharge. Exposures Noninvasive cardiac testing performed within 3 days of an ED evaluation for suspected acute coronary syndrome. Main Outcomes and Measures The primary outcome was composite risk of death or acute MI, within 30 days of an ED discharge. Results A total of 79 040 patients were evaluated in this study, of whom 57.7% were female. The mean (SD) age of the cohort was 57 (16) years, and 16 164 patients (21%) had completed early NIT. The absolute risk of death or MI within 30 days was low (<1%). Early NIT had the minor benefit of reducing the absolute composite risk of death or MI (0.4% [95% CI, −0.6% to −0.3%]), and, separately, of death (0.2% [95% CI, −0.2% to −0.1%]), MI (−0.3% [95% CI, −0.5% to −0.1%]), and major adverse cardiac event (−0.5% [95% CI, −0.7% to −0.3%]). The number needed to treat was 250 to avoid 1 death or MI, 500 to avoid 1 death, 333 to avoid 1 MI, and 200 to avoid 1 major adverse cardiovascular event within 30 days. Subgroup analysis revealed a number needed to treat of 14 to avoid 1 death or MI in the subset of patients with elevated troponin. Conclusions and Relevance Early NIT was associated with a small decrease in the risk of death or MI in patients admitted to the ED with suspected acute coronary syndrome, but this clinical strategy may not be optimal for most patients given the large number needed to treat