The Asthma Predictive Index (API), generated from long-term longitudinal studies of children enrolled at birth, identifies the following risk factors for developing persistent asthma among children younger than 3 years of age who have had four or more episodes of wheezing that lasted more than 1 day and affected sleep during the previous year:

The modified API adds documented environmental allergy to house dust mites, dogs, or cats as major criteria and allergy to milk, egg, or peanut as minor criteria. These additions are helpful in predicting patients more likely to have persistent symptoms.

^{Adapted from the National Heart, Lung, and Blood Institute National Asthma Education and Prevention Program. Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma: Full Report 2007. Bethesda, MD: NHLBI; 2007:282. http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf Accessed December 12, 2011}