Index predicts asthma in high-risk preschool children

Researchers have shown that the modified Asthma Predictive Index (mAPI) has high predictive value for future asthma development, when applied in the first 3 years of life.

The team, led by Daniel Jackson (University of Wisconsin, Madison, USA), analyzed data from the Childhood Origins of Asthma (COAST) cohort on 289 children with family history of allergy and/or asthma who were followed up from birth.

The mAPI threshold requires the child to have had at least four wheezing episodes in a year as well as at least one major criterion (parental asthma, atopic dermatitis, allergic sensitization to at least one aeroallergen) and two minor criteria (wheezing unrelated to colds, circulating eosinophils ≥4%, allergic sensitization to milk, eggs, or peanuts).

Applying the mAPI at years 1, 2, and 3, the team found that its predictive power increased over time, such that it was most accurate in year 3. They calculate that when a child at high risk for asthma, such as those from the COAST cohort, has a positive mAPI at age 3 years, the posttest probability of asthma at 6, 8, and 11 years is 90%, 96%, and 89%, respectively, compared with a pretest probability of 30%.

When the team relaxed the criteria of the mAPI to only two or more wheezing episodes in a year, they found that the predictive power of positive test results decreased; the posttest probabilities were 87%, 85%, and 82% at years 6, 8, and 11, respectively.

However, they note that a negative result had poor predictive power irrespective of which version of the mAPI was used, being associated with a 23–29% posttest probability of asthma diagnosis during follow-up compared with a 30% pretest probability.

The team also reports that the mAPI could improve asthma prediction in an unselected sample with a lower pretest probability, although to a lesser degree than for high-risk children. For a pretest probability of 11% (derived from a previous study), a positive mAPI at year 3 was associated with a posttest probability of asthma of 67%, 62%, and 57% at years 6, 8, and 11, respectively.

Writing in the Journal of Allergy and Clinical Immunology In Practice, Jackson et al say that the mAPI has several advantages, including ease of clinical application.

“Although asthma prediction during early life remains challenging, the mAPI’s high predictive ability of school-age asthma after a positive test can have clinical value for identifying children at risk of asthma persisting into school age and beyond,” they comment.

“Ultimately, the findings in this study may help clinicians and scientists better identify at-risk children, allowing for earlier diagnosis and targeted prevention strategies.”

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