Study Validates Asthma Symptom Tracker

Susan London

November 11, 2013

The Asthma Symptom Tracker (AST) performs well for monitoring the status of asthma symptoms in the pediatric population over time, according to results from a 6-month longitudinal cohort study.

Flory L. Nkoy, MD, MPH, from the University of Utah, Salt Lake City, and colleagues assessed the tool's performance among 210 children aged 2 to 18 years who were admitted to the hospital because of their asthma.

During the hospitalization and for the 6 months thereafter, the children or their parents completed the AST, a paper-based tool designed to be used at home that combines weekly use of the Asthma Control Test questionnaire with a color-coded graph to visually display trends over time.

The results, published online November 11 in Pediatrics, showed that the AST had moderate test–retest reliability and good validity, determined by a high correlation of scores with Asthma Control Questionnaire scores.

The authors found that with each 1-point decrease (worsening) in the 25-point AST score, children had a 13% higher use of oral corticosteroids and were 23% more likely to have an unscheduled acute care visit for asthma.

In addition, children who had poor asthma control, as defined by a score of less than 15, had sharply higher use of use of oral steroids (odds ratio, 2.6) and odds of unscheduled hospital visits (odds ratio, 10.8).

"Our study demonstrates that the AST is a reliable, valid, and responsive tool for weekly, ongoing monitoring of asthma control," the researchers write. "We hope that use of the AST can facilitate care continuity and shift asthma care from the current reactive, acute model to a preventive, proactive model where assessments are made weekly and treatment decisions are tailored to patients' individual needs."

It remains to be determined whether use of the AST reduces asthma exacerbations, they acknowledge.

The study was conducted in an academic children's hospital in Salt Lake City among patients admitted with a primary diagnosis of asthma. Overall, the children had a median age of 5.0 years, and 60% were boys. Nearly three fourths of the weekly AST assessments were completed by the parents.

Study results showed that the AST had moderate test–retest reliability, with an intraclass correlation of 0.50 to 0.65. There also was strong internal consistency, as measured with Cronbach's alpha, both at baseline (0.70) and during the follow-up period (0.82 - 0.90).

In addition, the AST had good validity when scores were compared with Asthma Control Questionnaire scores, both at baseline (R, −0.80) and at 4 times during follow-up (R, −0.63 to −0.72).

The AST also showed good responsiveness to changes in symptoms over time: Each 1-point increase (worsening) in Asthma Control Questionnaire score was associated with a significant 2.65-point decrease in AST at baseline and a significant 3.11-point decrease in AST during follow-up.

The study was supported by the Agency for Healthcare Research and Quality, the National Cancer Institute, the National Center for Research Resources, and the National Center for Advancing Translational Sciences, National Institutes of Health. Dr. Nkoy and 3 coauthors receive salaries and travel support through an Agency for Healthcare Research and Quality grant, and 4 coauthors receive salary support through an Agency for Healthcare Research and Quality grant. The other authors have disclosed no relevant financial relationships.

Pediatrics. Published online November 11, 2013.

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