EARLY PREDICTION OF POOR RESPONSE IN ACUTE ASTHMA PATIENTS IN THE EMERGENCY DEPARTMENT

Study objectives: The aim of this study tvas to develop an acute asthm a index for utilization in the early differentiation between patients with poor and good therapeutic response in the emergency department (E D) setting. Setting: The ED of a large tertiary-care hospital in Monte video, Uruguay. Patients and design: The study included 145 consecutiv e adult patients (mean age [ +/- SEM], 33.4 +/- 0.97) who presented to an ED (analysis sample). The inclusion criteria were: (1) age between 18 and 50 years; (2) a peak expiratory Row rate (PEFR) or FEV1 below 35% of predicted; and (3) no history of chronic cough or cardiac, hepa tic, renal, or other medical disease. Interventions: All patients were treated with salbutamol delivered by metered-dose inhaler into a spac er device in four puffs actuated at 10-min intervals. The protocol inv olved 3 h of this treatment. After that time, patients with poor respo nse received hydrocortisone, 500 mg TV. The outcome was defined as the FEV1 after 3 h of treatment in a dichotomized form: less than or equa l to 45% of predicted = poor response, and >45% of predicted = good re sponse. Results: Biserial correlations between different variables and the outcome showed that PEER as percent of predicted and PEER variati on over baseline, both measured at 30 min, were the most important pre dictors of a good or poor response after 3 h of treatment. Next, we de veloped an acute asthma index using these predictive measures. A compa rison of index sensitivity, specificity, predictive values, and the ar ea under the receiver operating characteristic (ROC) curve across diff erent: cutoff scores indicates that a score of 4 results in the least error of classification (sensitivity = 0.79; specificity = 0.96; area under the ROC curve = 0.87; positive predictive value = 0.94; and nega tive predictive value = 0.86). To validate the developed index, we pro spectively studied a second sample of 77 consecutive patients (mean ag e 32.6 +/- 1.22 years) who presented for treatment of acute asthma (va lidation sample). The area under the ROC for the analysis sample tvas not greater than the validation sample area (p = 0.24). Thus, the vali dation sample showed similar levels of sensitivity and specificity, po sitive and negative predictive values, and area under the ROC curve (0 .80, 0.88, 0.85, 0.84, and 0.89, respectively), indicating the stabili ty of the model. Conclusions: The study suggested the predictive accur acy of a two-item bedside index. This acute asthma index provides a to ol for assessing acute asthma severity using objective criteria easily accessible to the ED physician.