Research Article: Death Certificates Underestimate Infections as Proximal Causes of Death in the U.S

Date Published: May 30, 2014

Publisher: Public Library of Science

Author(s): Sushant Govindan, Letitia Shapiro, Kenneth M. Langa, Theodore J. Iwashyna, Keitaro Matsuo.


Death certificates are a primary data source for assessing the population burden of diseases; however, there are concerns regarding their accuracy. Diagnosis-Related Group (DRG) coding of a terminal hospitalization may provide an alternative view. We analyzed the rate and patterns of disagreement between death certificate data and hospital claims for patients who died during an inpatient hospitalization.

We studied respondents from the Health and Retirement Study (a nationally representative sample of older Americans who had an inpatient death documented in the linked Medicare claims from 1993–2007). Causes of death abstracted from death certificates were aggregated to the standard National Center for Health Statistics List of 50 Rankable Causes of Death. Centers for Medicare and Medicaid Services (CMS)-DRGs were manually aggregated into a parallel classification. We then compared the two systems via 2×2, focusing on concordance. Our primary analysis was agreement between the two data sources, assessed with percentages and Cohen’s kappa statistic.

2074 inpatient deaths were included in our analysis. 36.6% of death certificate cause-of-death codes agreed with the reason for the terminal hospitalization in the Medicare claims at the broad category level; when re-classifying DRGs without clear alignment as agreements, the concordance only increased to 61%. Overall Kappa was 0.21, or “fair.” Death certificates in this cohort redemonstrated the conventional top 3 causes of death as diseases of the heart, malignancy, and cerebrovascular disease. However, hospitalization claims data showed infections, diseases of the heart, and cerebrovascular disease as the most common diagnoses for the same terminal hospitalizations.

There are significant differences between Medicare claims and death certificate data in assigning cause of death for inpatients. The importance of infections as proximal causes of death is underestimated by current death certificate-based strategies.

Partial Text

Conventional tabulations of death certificate data emphasize the underlying cause of death—usually chronic illness—but seem to have significant shortcomings with respect to both accuracy and methodology [1]–[3]. Furthermore, the current system may inadvertently lead to the impression that infectious etiologies are “solved problems” in the developed world, despite the efforts by some to contest this view [4], [5]. Indeed, recent Eurostat Cause of Death tabulations do not even include an infectious category in the most accessible presentation [6]. Nonetheless, infectious etiologies remain a major driver of hospitalization [7], and with over forty percent of deaths in the U.S. occurring during hospitalizations [8], it is plausible that the true importance of infections in hospital associated mortality is less apparent in conventional death certificate data.

Data were derived from the nationally-representative HRS study, an NIH-funded longitudinal cohort study that has been ongoing since 1992. Hospitalization data was from the linked HRS-Medicare files. All HRS respondents are followed in the National Death Index, as well. The University of Michigan Institutional Review Board approved this work. Patients provided informed consent on enrollment in the HRS and again for linkage to Medicare claims.

Overall, 2074 inpatient deaths were included in our analysis; the demographics for the cohort can be seen in Table 1. Mean age at death was 80.4, and 52.2% were female.

Our study demonstrates that death certificates and hospital records paint distinct and complementary impressions about mortality. Death certificate data currently emphasizes the burdens of chronic disease. However, a clear majority of deaths occur during hospitalizations for reasons quite different from the reported underlying cause of death. This suggests that national mortality data often understate the proximal cause of death during that terminal hospitalization; specifically, there appears to be a neglect of the proximal role of infections and sepsis, particularly in older adults. From 17 to 19% of inpatient deaths attributed to heart disease, cancer and stroke by death certificates nonetheless occur during hospitalizations for infections. A balanced approach to harm mitigation for these chronic diseases still involves attention to and advances in the care of acute infections.