State differences in the reporting of 'unspecified stroke' on death certificates: implications for improvement

Little is known about the comparability of stroke subtype mortality across states. We conducted a cross-sectional descriptive study to examine state differences in the reporting of "unspecified stroke" on death certificates in the United States.

The number of deaths from different subtypes of stroke in each state for the years 2007 to 2009 were obtained from the CDC WONDER online databases. We calculated the percentage of stroke deaths classified as unspecified stroke (International Classification of Diseases, 10th Revision [ICD-10] code I64) among all stroke deaths (ICD-10 codes I60-I69) for each state.

Of 398 942 people who died from stoke in the United States between 2007 and 2009, in 209 933 (53%) cases, the medical certifier did not specify whether the stroke was hemorrhage or infarction on the death certificate. There were 44 states in which the percentage of unspecified stroke among all strokes was ≥50 and 20 states in which the percentage was ≥55%. The percentage was lowest in the District of Columbia (46%) and highest in Oklahoma (64%). The state variation in the proportion of unspecified stroke decreased with age of the deceased. The state percentage of unspecified stroke correlated most with the state percentage of cerebral infarction and other and sequelae of cerebrovascular disease.

Owing to the high percentage and state variation in the reporting of unspecified stroke on death certificates, the comparability of stroke subtype mortality is threatened. Querying of medical certifiers for more specific information for better coding is needed.