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Does date stamping ICD-9-CM codes increase the value of clinical information in administrative data?
Laurent G Glance1, Andrew W Dick, Turner M Osler
1Department of Anesthesiology, University of Rochester Medical Center, Rochester, NY 14642, USA.
Insights
Comorbidity measures misclassify many diagnoses. Using condition present at admission (CPAA) data significantly improves the accuracy of the Dartmouth-Charlson index and Elixhauser algorithm for mapping International Classification of Diseases (ICD-9-CM) codes.
Area of Science:
- Medical Informatics
- Health Services Research
- Clinical Epidemiology
Background:
- Comorbidity measures aim to categorize diagnoses, excluding complications.
- Administrative data with condition present at admission (CPAA) indicators can improve accuracy.
- Accurate mapping of International Classification of Diseases (ICD-9-CM) codes is crucial for research and clinical applications.
Purpose of the Study:
- To evaluate the misclassification rates of ICD-9-CM codes by the Dartmouth-Manitoba adaptation of the Charlson index and the Elixhauser comorbidity algorithm.
- To assess the impact of condition present at admission (CPAA) data on diagnostic category mapping accuracy.
Main Methods:
- Analysis of 178,838 patient admissions from the California State Inpatient Database (CA SID) in 2000.
- Utilized the condition present at admission (CPAA) modifier as the gold standard for validation.
- Compared diagnostic category mapping using the Dartmouth/Charlson index and the Elixhauser comorbidity measure against CPAA data.
Main Results:
- The Dartmouth/Charlson index underestimated key conditions, including hemiplegia/paraplegia (70%) and myocardial infarction (65%).
- The Elixhauser algorithm misclassified complications as pre-existing conditions in significant proportions, such as coagulopathies (43%) and fluid/electrolyte disorders (25%).
- Specific conditions like congestive heart failure (CHF) and cardiac arrhythmias showed notable misclassification rates with both algorithms.
Conclusions:
- Incorporating the condition present at admission (CPAA) modifier into administrative data substantially enhances diagnostic mapping accuracy.
- The Dartmouth/Charlson index and Elixhauser algorithm's ability to accurately map ICD-9-CM codes is significantly improved with CPAA data.
- This enhancement is vital for reliable comorbidity assessment and research utilizing administrative healthcare databases.
Context:
Comorbidity measures are designed to exclude complications when they map International Classification of Diseases (ICD-9-CM) codes to diagnostic categories. The use of data fields that indicates whether each secondary diagnosis was present at the time of hospital admission may lead to the more accurate identification of preexisting conditions.
Objective:
To examine the rate of misclassification of ICD-9-CM codes into diagnostic categories by the Dartmouth-Manitoba adaptation of the Charlson index and by the Elixhauser comorbidity algorithm.
Data Source:
Analysis of 178,838 patients in the California State Inpatient Database (CA SID) admitted in 2000 for one of seven major medical and surgical conditions. The CA SID includes a condition present at admission (CPAA) modifier for each ICD-9-CM code.
Study Design:
The Dartmouth/Charlson index and the Elixhauser comorbidity measure were used to map the ICD-9-CM codes into diagnostic categories for patients in each study population. We calculated the misclassification rate for each mapping algorithm, using information from the CPAA as the "gold standard."
Principal Findings:
The Dartmouth/Charlson index underestimated the prevalence of hemiplegia/paraplegia by 70 percent, cerebrovascular disease by 70 percent, myocardial infarction by 65 percent, congestive heart failure (CHF) by 45 percent, and peptic ulcer disease by 34 percent. The Elixhauser algorithm misclassified complications as preexisting conditions for 43 percent of the coagulopathies, 25 percent of the fluid and electrolyte disorders, 18 percent of the cardiac arrhythmias, 18 percent of the cardiac arrhythmias, and 9 percent of the cases of CHF.
Conclusion:
Adding the CPAA modifier to administrative data would significantly enhance the ability of the Dartmouth/Charlson index and of the Elixhauser algorithm to map ICD-9-CM codes to diagnostic categories accurately.
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