Measuring respiratory symptoms in moderate/severe asthma: evaluation of a respiratory symptom tool, the E-RS®: COPD in asthma populations

Maggie Tabberer; Robyn von Maltzahn; Elizabeth D Bacci; Hayley Karn; Ray Hsieh; Timothy A Howell; Zelie Bailes; Andrew Fowler; Laurie Lee; Lindsey T Murray

doi:10.1186/s41687-021-00338-6

Measuring respiratory symptoms in moderate/severe asthma: evaluation of a respiratory symptom tool, the E-RS®: COPD in asthma populations

J Patient Rep Outcomes. 2021 Oct 10;5(1):104. doi: 10.1186/s41687-021-00338-6.

Authors

Affiliations

¹ GSK House, 980 Great West Road, Brentford, Middlesex, TW8 9GS, UK. margaret.x.tabberer@gsk.com.
² GSK House, 980 Great West Road, Brentford, Middlesex, TW8 9GS, UK.
³ Evidera, Patient-Centered Research, 615 2nd Avenue, Seattle, WA, 98104, USA.
⁴ Evidera, Patient-Centered Research, 201 Talgarth Road, London, W6 8BJ, UK.
⁵ Evidera, Patient-Centered Research, 7101 Wisconsin Avenue, Bethesda, MD, 20814, USA.
⁶ GSK, 1250 S Collegeville Road, Collegeville, PA, 19426, USA.

Abstract

Background: Symptom constructs included in the Evaluating Respiratory Symptoms in Chronic Obstructive Pulmonary Disease (E-RS®: COPD) tool may be relevant to patients with asthma. The purpose of this study was to evaluate content validity and psychometric performance of the E-RS: COPD in moderate/severe asthma patients.

Methods: Content validity of the E-RS: COPD was evaluated in patients with moderate/severe asthma using concept elicitation and cognitive debriefing interviews. Secondary analyses using data from two clinical trials in patients with moderate/severe asthma evaluated the factor structure of the E-RS: COPD plus two supplementary items (wheeze; shortness of breath with strenuous physical activity) and assessed psychometric properties of the tool, which will be referred to as E-RS®: Asthma when used in asthma populations.

Results: Qualitative interviews (N = 25) achieved concept saturation for asthma respiratory symptoms. Concepts in the E-RS: COPD were relevant to patients and instructions were understood. Most patients (19/25; 76%) reported experiencing all concepts in the E-RS: COPD; no patients indicated missing symptoms. Secondary analyses of clinical trial data supported the original factor structure (RS-Total and three symptom-specific subscales). The two supplemental items did not fit with this factor structure and were not retained. RS-Total and subscale score reliability was high (internal consistency [α] > 0.70). Validity was demonstrated through significant (P < 0.0001) relationships with the St George's Respiratory Questionnaire (SGRQ) and Asthma Symptom Severity scale. E-RS: Asthma was responsive to change when evaluated using SGRQ, Patient Global Impression of Change and Asthma Quality of Life Questionnaire as anchors (P < 0.0001). Clinically meaningful change thresholds were also identified (RS-Total: - 2.0 units).

Conclusions: The E-RS: Asthma is reliable and responsive for evaluating respiratory symptoms in patients with moderate/severe asthma.

Keywords: Asthma; Content validity; Patient-reported outcome; Psychometric; Qualitative; Reliability; Respiratory symptoms; Responsiveness; Validity.