This asthma predictive index (API) calculator evaluates the likelihood of active asthma diagnosis during school years in children aged three and less with recurrent wheezing. Below the form there is in depth information on the criteria used and instructions on the result.


Number of wheezing episodes per year


API major criteria


API minor criteria

How does this asthma predictive index (API) calculator work?

This health tool is designed to provide a rapid answer to the likelihood of pediatric patients of three years or less, of developing childhood asthma during the school years.

The asthma predictive index brings together several variables that have been found relevant to asthma in other studies as well:

■ Number of wheezing episodes per year:

- Less than three;

- Three or more.

■ API major criteria:

- Family history (parent) with asthma;

- Patient diagnosed with eczema (atopic dermatitis).

■ API minor criteria:

- Diagnosed sensitivity to allergens in the air (demonstrated through positive skin prick tests or blood tests to a series of allergens such as dust mites, molds, weeds etc.);

- Wheezing present apart from colds;

- Greater than 4% blood eosinophils.

Subsequent validation studies have followed and proved a good specificity of the method, however, the API is not considered a screening tool for later asthma diagnosis for all types of pediatric patients and is best used in cases with recurrent wheezing episodes present.

Asthma Predictive Index (API) interpretation

The positive - stringent API requires:

■ Three or more episodes of wheezing per year during the first three years.

■ At least one major criteria or at least two of the minor criteria.

This result is associated with a 77% chance of diagnosed active asthma in the school years.

The positive – loose API requires:

■ Less than three episodes of wheezing per year in the first three years of life.

■ At least one major criteria or at least two of the minor criteria.

In the derivation study, 59% of patients with positive - loose API were diagnosed with active asthma.

Asthma predictive index results in the API calculator that don’t validate either of the above are considered negative and carry a chance of less than 3% of diagnosed asthma in the following years.

Asthma diagnostic in children

This type of diagnosis is often less specific due to the symptoms that are variable and due to the high chance of other wheezing disorders coexisting.

Misdiagnosis occurs with the following conditions: chronic bronchitis, wheezy bronchitis, recurrent pneumonia or gastroesophageal reflux, amongst others.

The API is required to delineate wheezing as predictor of asthma with the naturally occurring wheezing symptom in approximately 40% of all children.

Because there are no accurate testing methods available, clinical presentation remains the only option of prediction. With the application of such an index, cases with respiratory conditions associated with future asthma diagnosis can benefit from medical relief.

There is also available a modified version of API (mAPI), which adds another minor criteria, that of diagnosed food allergies.


1) Castro-Rodríguez JA, Holberg CJ, Wright AL, Martinez FD. (2000) A clinical index to define risk of asthma in young children with recurrent wheezing. Am J Respir Crit Care Med; 162(4 Pt 1):1403-6.

2) Leonardi NA, Spycher BD, Strippoli MP, Frey U, Silverman M, Kuehni CE. (2011) Validation of the Asthma Predictive Index and comparison with simpler clinical prediction rules. J Allergy Clin Immunol. 2011 Jun;127(6):1466-72.

3) Castro-Rodriguez JA. (2011) The Asthma Predictive Index: early diagnosis of asthma. Curr Opin Allergy Clin Immunol; 11:157–161.

4) Akl E, Irani AM, Amin P, Levin L, Epstein T. (2014) Optimum Predictors of Childhood Asthma: Persistent Wheeze or the Asthma Predictive Index? J Allergy Clin Immunol Pract; 2(6):709–715.

28 Aug, 2016