The maximum symptom day (MSD), which has never been validated, yet has been used as a measure of asthma symptom control in inner-city populations, was recently determined to be reliable, responsive, and valid, according to a study published in the Journal of Allergy and Clinical Immunology.

Researchers used outcome data from the Mouse Allergen and Asthma Intervention Trial (n=350), which evaluated participants every 3 months for 1 year, to assess the reliability, validity, responsiveness, and predictive characteristics of the MSD. The MSD was defined as the largest value of the number of days in the prior 2 weeks that a participant reports cough, wheezing, or shortness of breath, slowed activities because of these symptoms, or nocturnal awakening as a result of these symptoms. Data included the MSD, days of rescue inhaler use in the prior 2 weeks, unanticipated asthma-related healthcare use and oral steroid use in the prior 3 months, and the Childhood Asthma Control Test (C-ACT; ages 5-11), Asthma Control Test (AC; ages 12-17), and Pediatric Asthma Therapy Assessment Questionnaire-Control Subscale (ATAQ-Control).

Internal consistency reliability was assessed by Cronbach α at all visits. Test-retest reliability was assessed by the intraclass correlation coefficient in individuals who had stable control on the ACT/C-ACT. Between baseline and the 6-month visit, this was 0.57 and 0.55 between the 6-month and 12-month visit, which indicated moderate test-retest reliability.

Criterion validity was demonstrated by identifying significant Spearman correlations between MSD and ACT/C-ACT scores, ATAQ-Control scores, and days of rescue inhaler use at all visits. The absolute mean correlations with the ACT, C-ACT, and ATAQ-Control scores were 0.71, 0.52, and 0.53, respectively.

Predictive validity was confirmed by demonstrating significant associations between MSD and risk for acute healthcare use or corticosteroid need in the following 3 months (1-day increase in MSD = 4% increase in risk for an acute care encounter; relative risk, 1.04 [95% CI, 1.02-1.06]; P <.01).

“[T]he maximum symptom day is a reliable, responsive, and valid measure of asthma symptomatology that is consistently correlated with other measures of asthma control among inner-city populations,” the researchers wrote. “Increases in maximum symptom day were associated with increased risk of subsequent asthma-related acute healthcare utilization and use of corticosteroids, without floor or ceiling effects.”

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Reference

Wu TD, Perzanowski M, Peng RD, et al. Validation of the maximum symptom day among children with asthma [published online October 18, 2018]. J Allergy Clin Immunol. doi:10.1016/j.jaci.2018.10.008