To the Editor: Two articles in the March 1 issue1,2 attempt to evaluate our asthma predictor index.3 There are important differences between these studies and our study. We found that careful standardization of patient evaluation was essential because several of the index factors were subject to interobserver variability. Also, it was necessary to limit the length of emergency room therapy because it could influence outcome. Finally, we carefully standardized the treatment protocol since variations in treatment, especially the use of corticosteroids, made it difficult to distinguish between the predictive accuracy of the index and the effects of variable treatment regimens. © 1984, Massachusetts Medical Society. All rights reserved.