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Accuracy of coding for possible warfarin complications in hospital discharge abstracts
T Arnason1, P S Wells, C van Walraven
1Ottawa Health Research Institute-Clinical Epidemiology Program, Canada.
Insights
Hospital discharge abstracts accurately identify major bleeding and thromboembolism complications when International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes are used. This supports using administrative data for warfarin complication studies.
Area of Science:
- Medical Informatics
- Health Services Research
- Pharmacovigilance
Background:
- Hospital discharge abstracts are potential sources for identifying warfarin complications.
- Accurate coding of bleeding and thromboembolic events is crucial for utilizing these abstracts.
Purpose of the Study:
- To evaluate the accuracy of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for bleeding and thromboembolic diagnoses.
- To determine the reliability of administrative data for studying warfarin-associated complications.
Main Methods:
- A random sample of 616 patient discharge records from a tertiary care hospital were reviewed.
- Gold-standard coding was established by a blinded abstractor using explicit diagnostic criteria.
- Sensitivity, specificity, and predictive values of ICD-9-CM codes were calculated for bleeding and thromboembolism.
Main Results:
- ICD-9-CM codes demonstrated high sensitivity and specificity for bleeding (93% and 88%) and major bleeding (94% and 83%).
- Thromboembolism coding showed high sensitivity (97%) but lower specificity (74%), with improved positive predictive value (87%) for a subgroup.
- The study reviewed 616 medical records, identifying 352 bleeding events and 188 thromboembolic events.
Conclusions:
- Discharge abstracts can reliably identify patients with major bleeding or thromboembolism in this center.
- If coding quality is consistent, ICD-9-CM codes are suitable for population-based studies on warfarin complications using administrative databases.
Background:
Hospital discharge abstracts could be used to identify complications of warfarin if coding for bleeding and thromboembolic events are accurate.
Objectives:
To measure the accuracy of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9CM) codes for bleeding and thromboembolic diagnoses.
Setting:
University affiliated, tertiary care hospital in Ottawa, Canada.
Patients:
A random sample of patients discharged between September 1999 and September 2000 with an ICD-9-CM code indicating a bleeding or thromboembolic diagnosis.
Methods:
Gold-standard coding was determined by a trained chart abstractor using explicit standard diagnostic criteria for bleeding, major bleeding, and acute thromboembolism. The abstractor was blinded to the original coding. We calculated the sensitivity, specificity, positive, and negative predictive values of the original ICD-9CM codes for bleeding or thromboembolism diagnoses.
Results:
We reviewed 616 medical records. 361 patients (59%) had a code indicating a bleeding diagnosis, 291 patients (47%) had a code indicating a thromboembolic diagnosis and 36 patients (6%) had a code indicating both. According to the gold standard criteria, 352 patients experienced bleeding, 333 experienced major bleeding, and 188 experienced an acute thromboembolism. For bleeding, the ICD-9CM codes had the following sensitivity, specificity, positive and negative predictive values [95% CI]: 93% [90-96], 88% [83-91], 91% [88-94], and 91% [87-94], respectively. For major bleeding, the ICD-9CM codes had the following sensitivity, specificity, positive and negative predictive values: 94% [91-96], 83% [78-87], 87% [83-90], and 92% [88-95], respectively. For thromboembolism, the ICD-9CM codes had the following sensitivity, specificity, positive and negative predictive values: 97% [94-99], 74% [70-79], 62% [57-68], and 98% [96-99], respectively. By selecting a sub-group of ICD-9CM codes for thromboembolism, the positive predictive value increased to 87%.
Conclusion:
In our centre, the discharge abstract could be used to identify and exclude patients hospitalized with a major bleed or thromboembolism. If coding quality for bleeding is similar in other hospitals, these ICD-9-CM diagnostic codes could be used to study population-based warfarin-associated hemorrhagic complications using administrative databases.
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