Rebecca R Saff1, Carlos A Camargo2, Sunday Clark3, Susan A Rudders4, Aidan A Long5, Aleena Banerji5. 1. Division of Rheumatology, Allergy, and Immunology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Mass. Electronic address: rsaff@partners.org. 2. Division of Rheumatology, Allergy, and Immunology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Mass; Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Mass. 3. Department of Emergency Medicine, Weill Cornell Medical College, New York, NY. 4. Division of Asthma and Allergy, Department of Pediatrics, Rhode Island Hospital, Alpert School of Medicine at Brown University, Providence, RI. 5. Division of Rheumatology, Allergy, and Immunology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Mass.
Abstract
BACKGROUND: The epidemiology of allergic drug reactions is poorly understood due, in large part, to difficulty in identifying true cases in population data sets. Use of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes is a potentially valuable approach that requires formal evaluation. OBJECTIVE: To better understand the utility of ICD-9-CM codes for identification of allergic drug reactions, including the validation of specific codes by chart review. METHODS: We reviewed randomly sampled medical records of patients treated in the emergency department (ED) between January 1, 2001, and December 31, 2006, with ICD-9-CM codes for drug allergy and E codes (E930-949) for adverse drug reactions. RESULTS: During the 6-year period, 11,130 charts were identified by ICD-9-CM and E codes and 1,634 were reviewed. Allergic drug reactions were found in 444 (27%) of the reviewed ED visits. The codes that identified the highest percentage of true allergic drug reactions were dermatitis due to drug (693.0; 87%), adverse reaction to drug (995.2; 52%), and anaphylaxis (995.0; 38%). Patients with both an ICD-9-CM code and an E code had a high likelihood of having an allergic drug reaction (76%). Most allergic drug reactions were attributed to antibiotics (42%), intravenous contrast (7%), and nonsteroidal anti-inflammatory drugs (6%). The estimated frequency of allergic drug reactions increased from 0.49% of ED visits in 2001 to 0.94% in 2012. CONCLUSIONS: Specific ICD-9-CM and E codes can be used in combination to identify allergic drug reactions. Further study of these codes in the inpatient and outpatient settings is necessary to better understand the utility of diagnosis codes for improving epidemiologic research on drug allergy.
BACKGROUND: The epidemiology of allergic drug reactions is poorly understood due, in large part, to difficulty in identifying true cases in population data sets. Use of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes is a potentially valuable approach that requires formal evaluation. OBJECTIVE: To better understand the utility of ICD-9-CM codes for identification of allergic drug reactions, including the validation of specific codes by chart review. METHODS: We reviewed randomly sampled medical records of patients treated in the emergency department (ED) between January 1, 2001, and December 31, 2006, with ICD-9-CM codes for drug allergy and E codes (E930-949) for adverse drug reactions. RESULTS: During the 6-year period, 11,130 charts were identified by ICD-9-CM and E codes and 1,634 were reviewed. Allergic drug reactions were found in 444 (27%) of the reviewed ED visits. The codes that identified the highest percentage of true allergic drug reactions were dermatitis due to drug (693.0; 87%), adverse reaction to drug (995.2; 52%), and anaphylaxis (995.0; 38%). Patients with both an ICD-9-CM code and an E code had a high likelihood of having an allergic drug reaction (76%). Most allergic drug reactions were attributed to antibiotics (42%), intravenous contrast (7%), and nonsteroidal anti-inflammatory drugs (6%). The estimated frequency of allergic drug reactions increased from 0.49% of ED visits in 2001 to 0.94% in 2012. CONCLUSIONS: Specific ICD-9-CM and E codes can be used in combination to identify allergic drug reactions. Further study of these codes in the inpatient and outpatient settings is necessary to better understand the utility of diagnosis codes for improving epidemiologic research on drug allergy.
Keywords:
Adverse drug reactions; Drug allergy; Drug hypersensitivity; Emergency department; Epidemiology; International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes
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