Asthma Predictive Index (API)

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.