Therapeutic risk-assessment model for identifying patients with adverse drug reactions

The association between factors that place patients at risk for adverse drug reactions (ADRs) and the occurrence of ADRs was examined, and a therapeutic risk-assessment model was developed. Theoretical risk factors for ADRs to digoxin and theophylline were identified through the literature by researchers at a private tertiary-care hospital. Data were then collected from two groups of 67 patient charts each during a 15-month period. One group of charts represented patients who had experienced an ADR to digoxin or theophylline. The other group represented matched control patients who had not experienced an ADR to either drug. ICD-9-CM (International Classification of Diseases, 9th Revision, Clinical Modifications) ADR codes were assigned by medical records department personnel, and the ADRs were verified by using the Naranjo algorithm. Seven risk factors for each drug were found to be significantly associated with ADRs. A serum digoxin concentration greater than 2.5 ng/mL and elevated blood urea nitrogen were the two best predictors of an ADR to digoxin. The probability of experiencing an ADR to digoxin was 94.1% for a patient with both of these risk factors. A serum theophylline concentration greater than 25 micrograms/mL was the greatest predictor of an ADR to theophylline; the probability of experiencing an ADR to theophylline was 85.2% if a patient had that risk factor. The sensitivity and specificity of the therapeutic risk-assessment model were 92.9% and 61.8%, respectively, for digoxin and 95.8% and 84.0%, respectively, for theophylline. Several laboratory-based screening criteria demonstrated an ability to predict ADRs to digoxin and theophylline.