Diagnostic E-codes for commonly used, narrow therapeutic index medications poorly predict adverse drug events
Meyers Primary Care Institute; Department of Medicine, Division of Geriatric Medicine
Adverse Drug Reaction Reporting Systems; Aged; Anti-Arrhythmia Agents; Anticoagulants; Anticonvulsants; Cross-Sectional Studies; Digoxin; Forms and Records Control; Hospitalization; Humans; International Classification of Diseases; Medical Records; Patient Discharge; Pennsylvania; Pharmaceutical Preparations; Phenytoin; Warfarin
Health Services Research | Primary Care
OBJECTIVE: We sought to examine the validity of specific hospital discharge codes in identifying drug toxicity precipitating hospitalization, among elderly users of high-risk medications.
STUDY DESIGN AND SETTING: We conducted a cross-sectional evaluation assessing the diagnostic test characteristics of International Classification of Diseases-9 External-Cause-of-Injury codes (E-codes) compared with a reference standard of medical record review. This study was nested within a prospective cohort of elders using warfarin, digoxin, or phenytoin as identified in the Pharmaceutical Assistance Contract for the Elderly benefit program.
RESULTS: We identified 4,803 subjects contributing 11,409 person-years of exposure to at least one of three drug groups. Subjects experienced 8,756 hospitalizations, of which 304 were deemed, by expert review, to be a result of an adverse event of warfarin, digoxin, or phenytoin. The sensitivity, specificity, and positive (PPVs) and negative predictive values for drug-specific E-codes were warfarin--25.5%, 98.3%, 46.6%, and 95.7%; digoxin--84.0%, 99.1%, 56.8%, and 99.8%; and phenytoin--86.7%, 98.7%, 59.1%, and 99.7%.
CONCLUSIONS: E-codes for digoxin and phenytoin have a high sensitivity, but E-codes for all three medications have poor PPVs, a result that might produce misclassification in studies based solely on discharge coding. Investigators should confirm such rare events via medical record review.
DOI of Published Version
J Clin Epidemiol. 2008 Jun;61(6):561-71. Epub 2008 Feb 14. Link to article on publisher's site
Journal of clinical epidemiology
Leonard CE, Haynes K, Localio AR, Hennessy S, Tjia J, Cohen A, Kimmel SE, Feldman HI, Metlay JP. (2008). Diagnostic E-codes for commonly used, narrow therapeutic index medications poorly predict adverse drug events. Meyers Primary Care Institute Publications. https://doi.org/10.1016/j.jclinepi.2007.08.003. Retrieved from https://escholarship.umassmed.edu/meyers_pp/435