A Better Asthma Prediction Tool for Preschoolers?

A simple screening tool based on cough, wheeze, and medication use flagged asthma risk in 3-year-olds with greater accuracy than standard strategies, researchers reported.

The CHILDhood Asthma Risk Tool (CHART) outperformed specialists’ assessments and the modified Asthma Predictive Index (mAPI) for predicting asthma diagnosis by age 5 in one cohort and was validated for prediction at ages 5 and 7 in two others, reported Padmaja Subbarao, MD, MSc, of the Hospital for Sick Children in Toronto, and colleagues in JAMA Network Open.

“CHART could be easily incorporated as a routine screening tool in primary care to identify children who need monitoring, timely symptom control, and introduction of preventive therapies,” the group suggested. This could “improve quality of life for patients and reduce the clinical and economic burden of asthma.”

Pragmatic and inexpensive screening tools are needed as the first step in screening for asthma, but the mAPI requires invasive testing, like blood or allergy skin prick tests, “which are challenging in young children,” Subbarao’s group noted. “Other tools, such as the Persistent Asthma Predictive Score, Predicting Asthma Risk in Children, or Pediatric Asthma Risk Score, either have been developed in children predisposed to asthma, require invasive tests, or are not validated in general populations.”

They developed CHART, which categorizes children into risk groups based on symptoms before age 3 and recommends follow-up actions for each group.

• High risk: two or more episodes of wheeze in the past year, concurrent with emergency department visits, hospitalizations, asthma medication, or frequent dry cough
• Moderate risk: multiple cough and wheeze episodes in the prior 12 months but no emergency care or hospitalization or asthma medication use
• Low risk: cough episodes alone or with no more than one episode of wheeze occurring in the prior 12 months, and no more than two wheeze episodes ever

High-risk children are flagged for physician evaluation for therapy, while moderate-risk kids get screened again in 6 months and low-risk kids get screened after 12 months.

Applying this to the 2,511 children (53% male) seen for their 3-year clinic visit in Canada in the CHILD Study from 2008 through 2012, 7% were classified as being at high risk, 24% at moderate risk, and 69% at low risk.

The performance of CHART was highest for prediction of persistent wheeze by age 5, with an area under the receiver operating characteristic curve (AUROC) of 0.94 (95% CI 0.90-0.97). In that regard, it outperformed physician diagnoses and the mAPI (sensitivity 91.1% vs 62.0% and 48.5%). All three prediction types had similar specificity and negative predictive value, although mAPI had the highest positive predictive value (PPV; 60.0% vs 43.4% with CHART).

CHART also had the best performance for predicting asthma diagnosis at age 5 (AUROC 0.73, sensitivity 50.0% vs 24.4% with mAPI and 43.5% for physicians) and emergency department visits or hospitalization for wheeze or asthma (AUROC 0.70, sensitivity 45.5% vs 25.0% with mAPI and 34.4% for physicians). CHART performed on par with the Pediatric Asthma Risk score for asthma prediction at age 5.

“Although CHART also had the highest sensitivity and AUROC for corticosteroid and bronchodilator use, mAPI had slightly higher specificity and PPV,” the researchers noted.

Validation in 2,185 children at age 5 in the general population Raine Study from Australia and 349 children in the high-risk population of the Canadian Asthma Primary Prevention Study (CAPPS) at age 7 showed similar performance of CHART, with AUROCs of 0.82 and 0.87.

“It is important to note that CHART is designed as a pragmatic screening tool to help busy primary care clinicians identify the small proportion of children at high risk for persistent wheezing (7% in our population) among all children who report wheeze (42% at any time point),” Subbarao and colleagues wrote. “Once children are identified as being at high risk, clinicians will need to evaluate this smaller group for both severity and endotype of asthma.”

Biomarkers, such as blood eosinophils, might help guide therapeutic choices, such as inhaled corticosteroids versus antileukotrienes in this age group, they added, and tools like CHART can help in narrowing the group who needs invasive and more expensive tests to just high-risk children.

Limitations of the study were the largely urban, albeit multiethnic, population of children and that the Raine Study and CAPPS didn’t have all the measures at preschool age to calculate mAPI.

“In addition, the sensitivity (50%) and PPV (41.5%) for asthma in CHART are suboptimal for a screening test,” the researchers noted. “The striking contrast to the high performance obtained for persistent wheeze suggests that this may be rooted in physicians’ hesitance to diagnose asthma at a young age.”