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The Acute Asthma Intensity Research Score (AAIRS) is a 7-component, 17-point (0 – 16 with 16 most severe) acute asthma exacerbation severity score. Components of the score include accessory muscle (suprasternal-sternocleidomastoid, intercostal, subcostal) retractions, air entry, wheezing, oxygen saturation on room air (>=95%, 0 points; 92 – 94%, 1 point; <92%, 2 points), and expiratory phase prolongation.1
We previously reported the performance of the AAIRS to measure baseline acute asthma exacerbation severity and responsiveness to change during treatment in a prospective cohort of 661 patients aged 5 – 17 years who were admitted to our tertiary children’s hospital emergency department with acute exacerbations.1 The criterion outcome measure for that analysis was %-predicted forced expiratory volume in 1-second (%FEV1).
In this study we sought to examine the performance of the AAIRS to predict hospital or pediatric intensive care unit (PICU) admission.2 In addition, we examined the performance of the AAIRS to predict %-predicted airway resistance by impulse oscillometry (%IOS), as well as to confirm prior findings of prediction of %FEV1 after recruitment of the entire cohort of 933 participants.
For each participant studied during an acute exacerbation in our pediatric emergency department we performed a comprehensive pulmonary examination and calculated the AAIRS before (baseline) and after 2 hours of treatment. Participants attempted spirometry for %FEV1 and measurement of %IOS using a CareFusion MasterScreen™ PFT system (CareFusion, Yorba Linda, CA) at each time point. The clinical team was not provided study data, including values for the AAIRS, and followed an asthma clinical practice guideline that used an unvalidated severity score. The study (protocol #080058) was approved by our institutional review board.
We assessed predictive validity with multivariable logistic regression models to examine whether the baseline AAIRS or 2-hour change of the AAIRS is associated with hospital or PICU admission, adjusted for age, gender, race and, for the change-of-AAIRS analysis, baseline AAIRS.3 Construct validity was assessed as the accuracy of the AAIRS to predict %FEV1 and %IOS at baseline. For these analyses we used multivariable linear regression with %FEV1 or %IOS as the outcome variable and the AAIRS, age, gender and race as predictor variables. Responsiveness was assessed as the ability of change of the AAIRS to predict change of %FEV1 and %IOS after 2 hours of treatment.3–6 We used multivariable linear regression models to examine 2-hour change of %FEV1 or %IOS with change of the AAIRS, adjusted for age, gender, race, baseline AAIRS and baseline %FEV1 or %IOS, respectively.
Of 806 unique participants amongst the cohort of 933 recruited participants, median [IQR] age was 8.9 [6.9, 11.3] years, 61% were male, 58% were African-American, and AAIRS was 5 [2, 8] at baseline and 2 [0, 5] at 2 hours. One-hundred forty-four (18%) were admitted to floor beds and 42 (5%) to the PICU. %FEV1 was 50 [36, 72; n = 469] at baseline and 61 [43, 77; n = 351] at 2 hours. Corresponding values for %IOS were 162 [125, 219; n = 174] at baseline and 125 [103, 159; n = 133] at 2 hours. The results of multivariable regression models used to assess the AAIRS are displayed in Table 1.
We found associations of the AAIRS with hospital or PICU admission. For example, a 1-point increase of the AAIRS at baseline was associated with 1.3 times the odds for hospital floor admission. Similarly, beta-coefficients were clinically meaningful for the associations of the AAIRS with %FEV1 and %IOS at baseline and in response to treatment. For example, a 1-point increase in the AAIRS score at baseline is associated with a decrease of %FEV1 of approximately 5%.
Additionally, our children’s hospital now uses the AAIRS as part of an asthma clinical practice guideline according to three levels of severity: mild (AAIRS 1 – 6); moderate (AAIRS 7 – 11); and severe (AAIRS 12 – 16). Hospitalization rates according to these severity levels for participants at baseline were: mild 72/517 (14%); moderate 101/267 (38%); and severe 13/22 (59%). Corresponding hospitalization rates for severity levels amongst participants remaining in the emergency department at 2 hours were: mild 111/493 (22%); moderate 58/79 (73%); and severe 1/1 (100%).
In summary, the AAIRS demonstrates predictive validity for hospitalization and PICU admission as well as construct validity and responsiveness to clinically meaningful changes of lung function. Expert guidelines recommend use of a comprehensive exacerbation severity score to determine which patients should be admitted to the hospital to improve patient care and resource utilization.7 The AAIRS might also complement pediatric and adult clinical prediction rules for asthma hospitalization.8,9 Knowledge of the baseline AAIRS and change in response to treatment might inform clinical decision-making at the bedside.
Research support: This research was supported by the National Institutes of Health: [K23 HL80005] (Dr. Arnold); NIAID [K24 AI77930] (Dr. Hartert); and NIH/NCRR [UL1 RR024975] (Vanderbilt CTSA).
This work was performed at the Monroe Carell Jr. Children’s Hospital at Vanderbilt, Vanderbilt University Medical Center, Nashville, TN 37232.
Author Disclosure Statements: Dr. Arnold had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. The authors have no conflicts of interest to disclose.
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