What is the Asthma Predictive Index?

The seeds for writing about the Asthma Predictive Index (API) were planted in a blog post The Allergy Dude wrote about 2 years ago.  After reading my 2011 issues of the Journal of Allergy and Clinical Immunology, my interest was nurtured.  Many researchers have tried to produce a clinical prediction rule to help physicians and patients with asthma know how long their asthma would persist.  Researchers in Arizona, led by Jose A. Castro-Rodriguez, M.D., proposed the API in an article published in the year 2000.  The API was based on the patient's historical clinical facts, such as family history.  Note that the API should be applied to children ages 2 to 3 years old and tries to predict those with a high risk of persistence of asthma.  In 2007, the National Heart, Lung, Blood Institute (NHLBI)'s Expert Panel Report promoted use of the API.   Here is the Modified API:

High risk children (under age three) who have had four or more wheezing episodes in the past year that lasted more than one day, and affected sleep, are much more likely to have persistent (i.e. lifelong) asthma after the age of five, if they ALSO have either of the following:

One major criteria

~ Parent with asthma

~ Physician diagnosis of atopic dermatitis (often called eczema)

~ Evidence of sensitization to allergens in the air (i.e., positive skin tests or blood tests to allergens such as trees, grasses, weeds, molds, or dust mites)

OR

Two minor criteria

~ Evidence of food allergies

~ >4 percent blood eosinophilia (Increased numbers of white blood cells called eosinophils are made by the body to fight off allergic disease. They can collect in tissues and cause damage to the airways of the lung.)

~ Wheezing apart from colds.

If a child has 1 major criterion or 2 minor criteria, he or she has a 75% chance of having persistent asthma. Alternatively, if the child has a negative Modified Asthma Predictive Index, he or she has a 68% chance of not having persistent asthma past the early school-age years. In the April issue of the Journal of Allergy and Clinical Immunology, Dr. Castro-Rodriguez wrote about the API's "simplicity and relatively good likelihood ratio." The Allergy Dude thinks this is a good start and agrees that there is always room for improvement.  We'd like the chances to be well above 50%, or 50-50.

The API was mentioned again in the NHLBI's Strategic Plan 11/30/09 (page 10).  The plan points out that young children with recurrent wheezing are a treatment dilemma, as just 1/3 have persistent asthma after age 6:

Would daily therapy be appropriate for these children?
How can you identify and avoid unnecessary treatments for the remaining 2/3?

These are good questions.

There is no universal answers currently.  The Allergy Dude weighs the risks and benefits of continuing to treat children who wheeze intermittantly and usually opts to continue treatment, based on symptom control and spirometry data, until a prolonged period without symptoms and normal spirometry have occurred, before tapering treatment.  If you have questions, ask your doctor...