Validity of International Classification of Disease Codes to Identify Ischemic Stroke and Intracranial Hemorrhage Among Individuals With Associated Diagnosis of Atrial Fibrillation | Journal Scan

Study Questions:

What is the validity of International Classification of Disease-Ninth Revision (ICD-9) codes in stroke case ascertainment and for atrial fibrillation (AF) across three institutions?


Participating centers included Boston Medical Center (safety net hospital), Geisinger Health System (rural Pennsylvania), and the University of Alabama (academic center in the southeastern stroke belt). ICD-9 codes for ischemic stroke (433–434, 436) and intracranial hemorrhage (430–432) identified 1,812 stroke cases with an associated code for AF (427.31) from 2006 to 2010. Cases were vetted through chart review with final adjudication by a stroke neurologist.


The review considered 94.2% of ICD-9 identified stroke cases valid with decreased accuracy for concurrent AF diagnosis (82.28%) and stroke attributable to AF (72.8%). Among events with “without infarction” modifiers, 7.2% were valid strokes. ICD-9 stroke code accuracy did not differ by stroke type or site. Stroke code 434 displayed higher accuracy than 433 (94.4% vs. 85.2%; p < 0.01), and primary stroke codes were more accurate than nonprimary codes (97.2% vs. 83.7%; p < 0.0001).


The authors concluded that using ICD-9 stroke and AF codes to identify patients with stroke plus AF resulted in inaccuracies.


This study found less than optimal accuracy of ICD-9–coded stroke events when compared with the gold standard of medical record primary data review. This indicates that manual verification is indicated to confirm stroke events in the setting of AF so as to reduce biased estimates. In addition, these findings highlight the need for more rigorous methods to validate outcome events identified by ICD-9 codes in large administrative databases.

Clinical Topics: Arrhythmias and Clinical EP, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Atrial Fibrillation, Stroke, International Classification of Diseases, Intracranial Hemorrhages, Medical Records, Databases, Factual, Infarction

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