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Validity of hospital discharge diagnosis codes for stroke: the Atherosclerosis Risk in Communities Study
Sydney A Jones1, Rebecca F Gottesman1, Eyal Shahar1
1From the Department of Epidemiology (S.A.J., W.D.R.) and Department of Biostatistics (L.W.), Gillings School of Global Public Health, University of North Carolina at Chapel Hill; Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD (R.F.G.); and Epidemiology and Biostatistics Division, the University of Arizona College of Public Health, Tucson (E.S.).
Insights
Validating International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) stroke codes is crucial. A new American Heart Association/American Stroke Association (AHA/ASA) grouping showed similar accuracy but lower sensitivity than an alternative for identifying strokes.
Area of Science:
- Neurology
- Public Health
- Health Informatics
Background:
- Hospital discharge databases are widely used for research.
- Accurate coding of diagnoses, such as stroke, is essential for reliable data.
- International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) codes are frequently used in these databases.
Purpose of the Study:
- To assess the accuracy of ICD-9-CM codes for identifying stroke events.
- To compare the validity of different ICD-9-CM code groupings for stroke research.
- To evaluate the performance of the American Heart Association/American Stroke Association (AHA/ASA) 2013 stroke code categories.
Main Methods:
- Utilized data from the Atherosclerosis Risk in Communities (ARIC) Study (1987-2010).
- Abstracted hospitalizations with relevant ICD-9-CM codes or stroke keywords in discharge summaries.
- Employed a computer algorithm and physician review for gold-standard classification of stroke types (ischemic, intracerebral hemorrhage, subarachnoid hemorrhage).
- Calculated positive predictive value (PPV) and sensitivity for ICD-9-CM code groupings.
Main Results:
- 33% of 4260 hospitalizations were confirmed strokes.
- The AHA/ASA code grouping demonstrated a PPV of 76% and 68% sensitivity.
- An alternative code grouping yielded a PPV of 72% and 83% sensitivity.
- Accuracy varied by stroke type, patient demographics (race, age), hospital type, and study site.
Conclusions:
- The new AHA/ASA stroke code grouping has comparable PPV but lower sensitivity than an alternative grouping.
- The accuracy of ICD-9-CM stroke codes is influenced by patient characteristics and geographic location.
- Refined coding strategies may be necessary to improve stroke identification in research databases.
Background And Purpose:
Characterizing International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) code validity is essential given widespread use of hospital discharge databases in research. Using the Atherosclerosis Risk in Communities (ARIC) Study, we estimated the accuracy of ICD-9-CM stroke codes.
Methods:
Hospitalizations with ICD-9-CM codes 430 to 438 or stroke keywords in the discharge summary were abstracted for ARIC cohort members (1987-2010). A computer algorithm and physician reviewer classified definite and probable ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. Using ARIC classification as a gold standard, we calculated the positive predictive value (PPV) and sensitivity of ICD-9-CM codes grouped according to the American Heart Association/American Stroke Association (AHA/ASA) 2013 categories and an alternative code grouping for comparison.
Results:
Thirty-three percent of 4260 hospitalizations were validated as strokes (1251 ischemic, 120 intracerebral hemorrhage, 46 subarachnoid hemorrhage). The AHA/ASA code groups had PPV 76% and 68% sensitivity compared with PPV 72% and 83% sensitivity for the alternative code groups. The PPV of the AHA/ASA code group for ischemic stroke was slightly higher among blacks, individuals <65 years, and at teaching hospitals. Sensitivity was higher among older individuals and increased over time. The PPV of the AHA/ASA code group for intracerebral hemorrhage was higher among blacks, women, and younger individuals. PPV and sensitivity varied across study sites.
Conclusions:
A new AHA/ASA discharge code grouping to identify stroke had similar PPV and lower sensitivity compared with an alternative code grouping. Accuracy varied by patient characteristics and study sites.
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