Asthma Predictive Index (API)

Evaluates risk of asthma diagnosis in the future for children aged three or less suffering from recurrent wheezing.

In the text below the calculator there is more information about the criteria used and on how the result is interpreted.

The asthma predictive index assesses the likelihood of pediatric patients of three years or less (suffering from recurrent wheezing), to be developing childhood asthma during the school years.

The API is based on the following criteria:

■ Number of wheezing episodes per year;

■ Family history;

■ Diagnosis of atopic dermatitis;

■ Diagnosed sensitivity to allergens in the air;

■ Greater than 4% blood eosinophils.

The API has three types of possible results:

■ Positive by stringent criteria (≥3 wheezing episodes AND 1 major OR 2 minor) which carries a 77% chance of diagnosed active asthma;

■ Positive by loose criteria (<3 wheezing episodes AND 1 major OR 2 minor), which carries a 59% of diagnosis;

■ Negative, which carries less than 3% chance of asthma diagnosis.


Number of wheezing episodes per year*


API major criteria


API minor criteria

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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.


API criteria

The model checks whether pediatric patients aged three or less who experience recurrent wheezing episodes are at risk of developing asthma in the following years.

API was created following a study conducted by José Castro-Rodríguez, who is an assistant professor of Pediatrics and family medicine at Pontifica Universidad Católica in Chile.

There are three types of criteria in the API:

1. Number of wheezing episodes per year, where the user can select either “Less than three” or “Three or more”.

The first may constitute part of the positive result by loose criteria whilst the latter may constitute part of the positive result by stringent criteria (subject to the other criteria being met).

2. API major criteria

- Family history (parent) with asthma;

- Patient diagnosed with eczema (atopic dermatitis).

3. API minor criteria

- Patient diagnosed with sensitivity to allergens in the air*;

- Wheezing present apart from colds;

- Greater than 4% blood eosinophils.

*Demonstrated through positive skin prick tests or blood tests to a series of allergens such as dust mites, mold, weeds etc.

Subsequent validation studies have shown that the index has good specificity, however, the method remains for usage in children of three and below, with recurrent wheezing episodes, rather than in all pediatric patients.

There is also a modified asthma predictive index version which adds an additional criteria that refers to food allergies.


Result interpretation

There are two types of positive (risk of developing childhood asthma) results, a positive stringent (77% asthma diagnosis risk) and a positive loose one (59% diagnosis risk).

Both positive results require at least one major criteria OR at least two of the minor criteria.

The difference is made by the number of wheezing episodes per year where:

■ Positive stringent criteria require three or more;

■ Positive loose criteria require less than three.

Asthma predictive index results that don’t validate either of the above are considered negative and are associated with less than 3% risk of diagnosed asthma in the following years.


Asthma diagnosis in children

Because symptoms are often variable and there is a high risk of other wheezing disorders coexisting, asthma diagnosis in children is highly specific.

Wheezing is also a naturally occurring symptom in approximately 40% of all children.

Clinical presentation remains the basis of diagnosis, therefore the application of criteria such as that in API can help standardize diagnosis and reveal the pediatric patients who might benefit, in the future, from medical relief.

Differential diagnosis often involves conditions such as chronic bronchitis, wheezy bronchitis, recurrent pneumonia or gastroesophageal reflux.


Original source

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

Other references

1. Leonardi NA, Spycher BD, Strippoli MP, Frey U, Silverman M, Kuehni CE. Validation of the Asthma Predictive Index and comparison with simpler clinical prediction rules. J Allergy Clin Immunol. 2011; 127(6):1466-72.e6.

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

Specialty: Pulmonology

System: Respiratory

Objective: Risk Predictor

Type: Index

No. Of Criteria: 6

Year Of Study: 2000

Abbreviation: API

Article By: Denise Nedea

Published On: April 13, 2017

Last Checked: April 13, 2017

Next Review: April 13, 2023