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Agreement between nosologist and cardiovascular health study review of deaths: implications of coding differences
Diane G Ives1, Paulraj Samuel, Bruce M Psaty
1Department of Epidemiology, Center for Aging and Population Health, University of Pittsburgh, Pennsylvania 15213, USA. ivesd@edc.pitt.edu
Insights
Death certificate coding for older adults shows moderate agreement with adjudicated causes, but significant discrepancies exist for dementia. Relying solely on death certificates may misclassify causes of death in elderly populations.
Area of Science:
- Gerontology
- Epidemiology
- Public Health
Background:
- Accurate determination of underlying cause of death is crucial for epidemiological studies and public health surveillance.
- The Cardiovascular Health Study (CHS) has collected extensive data on participants aged 65 and older since 1989.
- Previous studies have highlighted potential discrepancies in cause of death coding.
Purpose of the Study:
- To compare the accuracy of underlying cause of death coding by nosologists using death certificates versus adjudicated causes of death within the CHS cohort.
- To identify specific causes of death where coding discrepancies are most prevalent in older adults.
Main Methods:
- An observational study was conducted using data from the Cardiovascular Health Study (CHS).
- The CHS adjudicated the underlying cause of death for 3,194 participants aged 65 and older using medical records, death certificates, interviews, and autopsies.
- These adjudicated causes were compared to those assigned by a trained nosologist relying solely on death certificates.
Main Results:
- Overall moderate agreement was found between nosologist and CHS adjudicated causes of death (kappa varied by category).
- High agreement was observed for cancer (kappa=0.91), but lower agreement for coronary heart disease (kappa=0.61), stroke (kappa=0.59), COPD (kappa=0.58), dementia (kappa=0.40), and pneumonia (kappa=0.35).
- Significant undercounting of dementia as the underlying cause of death was noted in nosologist coding compared to CHS adjudication (3.5% vs. 10.6%).
Conclusions:
- Relying exclusively on death certificates for cause of death determination in older populations can lead to misclassification and bias.
- Observed changes in cause-specific mortality trends in the elderly may be influenced by coding methodologies rather than actual changes in disease incidence or fatality.
- Adjudicated causes of death provide a more accurate representation for research and public health initiatives concerning older adults.
Objectives:
To compare nosologist coding of underlying cause of death according to the death certificate with adjudicated cause of death for subjects aged 65 and older in the Cardiovascular Health Study (CHS).
Design:
Observational.
Setting:
Four communities: Forsyth County, North Carolina (Wake Forest University); Sacramento County, California (University of California at Davis); Washington County, Maryland (Johns Hopkins University); and Pittsburgh, Pennsylvania (University of Pittsburgh).
Participants:
Men and women aged 65 and older participating in CHS, a longitudinal study of coronary heart disease and stroke, who died through June 2004.
Measurements:
The CHS centrally adjudicated underlying cause of death for 3,194 fatal events from June 1989 to June 2004 using medical records, death certificates, proxy interviews, and autopsies, and results were compared with underlying cause of death assigned by a trained nosologist based on death certificate only.
Results:
Comparison of 3,194 CHS versus nosologist underlying cause of death revealed moderate agreement except for cancer (kappa=0.91, 95% confidence interval (CI)=0.89-0.93). kappas varied according to category (coronary heart disease, kappa=0.61, 95% CI=0.58-0.64; stroke, kappa=0.59, 95% CI=0.54-0.64; chronic obstructive pulmonary disease, kappa=0.58, 95% CI=0.51-0.65; dementia, kappa=0.40, 95% CI=0.34-0.45; and pneumonia, kappa=0.35, 95% CI=0.29-0.42). Differences between CHS and nosologist coding of dementia were found especially in older ages in the sex and race categories. CHS attributed 340 (10.6%) deaths due to dementia, whereas nosologist coding attributed only 113 (3.5%) to dementia as the underlying cause.
Conclusion:
Studies that use only death certificates to determine cause of death may result in misclassification and potential bias. Changing trends in cause-specific mortality in older individuals may be a function of classification process rather than incidence and case fatality.
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