Author + information
- Rahul Nanchal, MD∗ ( and )
- Gagan Kumar, MD
- ↵∗Division of Pulmonary and Critical Care, Department of Medicine, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, Wisconsin 53226
We thank Dr. Khoshchehreh and colleagues for their interest in our paper. As pointed out and addressed in our paper, we cannot completely exclude selection bias as a partial explanation of our findings. However, unmeasured differences in severity of illness are less likely to be an explanation of our findings because of 2 reasons. First, mortality differences were no longer apparent after adjusting for the differential utilization of revascularization procedures during weekdays. Second, differences in mortality persisted when we adjusted for severity of illness using surrogate markers such as shock and receipt of mechanical ventilation (1).
We agree that it is important to distinguish between ST-segment elevation myocardial infarction (STEMI) and non–ST-segment elevation myocardial infarction (NSTEMI) when performing such analyses. We therefore used International Classification of Diseases (ICD)-9-CM codes 410.x1, which denotes STEMI and initial episode of care. We excluded patients if they had an ICD-9-CM code denoting subendocardial myocardial infarction or NSTEMI (410.7). Using codes for STEMI, we found that 26.1% were admitted on weekends.
Moreover, the fact that we restricted our attention to STEMI, which is an exceedingly time-sensitive condition, makes it less likely that our findings merely reflect patients delaying care on the weekend, as suggested by Dr. Khoshchehreh and colleagues. Delay in care for STEMI would arguably bias our results toward finding no difference in mortality on weekdays and weekends, as receipt of cardiac catheterization in persons presenting late is unlikely to affect their outcomes. Further, during the years 2006 to 2008, weekend admissions still represented 26% of all admission; however, utilization of revascularization procedures rose and weekend-weekday mortality differences dissipated. These phenomena argue against selection bias as the sole explanation of our findings.
We believe that our method of inclusion using ICD-9-CM codes represents patients experiencing STEMI and that timing of cardiac catheterization remains an important measure of quality of care (2).
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation
- Kumar G.,
- Deshmukh A.,
- Sakhuja A.,
- et al.
- O'Gara P.T.,
- Kushner F.G.,
- Ascheim D.D.,
- et al.