ICD9 Codes Cannot Reliably Identify Hemorrhagic Transformation of Ischemic Stroke

Abstract

A major objective of inpatient stroke care is the prevention of medical and neurological complications, although rare, hemorrhagic transformation (HT) of an ischemic stroke (IS) can cause neurological deterioration and is associated with an increased risk of death.1 If HT can be reliably identified in administrative data, it could become a component of hospital quality benchmarks. Previous studies have used administrative data to define HT of IS; however, the accuracy of International Classification of Diseases, Ninth Revision ( ICD9 ) coding for this condition is unknown.2–4 Coding algorithms used in previous studies have varied, but all have required a discharge diagnosis of IS, defined by ICD9 code or Clinical Classification Software code, and a discharge ICD9 for intracranial hemorrhage. We aimed to determine the accuracy of ICD9 coding for HT after IS using the Greater Cincinnati/Northern Kentucky Stroke Study (GCNKSS). The purpose of the GCNKSS is to ascertain all strokes among a 5-county region that includes Cincinnati. Study personnel identified potential cases from January 1, 2005, through December 31, 2005, by screening emergency department encounters and inpatient admissions at 17 acute care hospitals for discharge ICD9 codes for stroke (430–436). Data are collected for all cases of IS, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage. Potential cases were excluded if they had a discharge/autopsy diagnosis …