Understanding and measuring symptoms and health status in asthma COPD overlap: content validity of the EXACT and SGRQ

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

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.

Reliability, validity and responsiveness of E-RS:COPD in patients with spirometric asthma-COPD overlap

BACKGROUND

The Evaluating Respiratory Symptoms in Chronic Obstructive Pulmonary Disease (E-RS:COPD) is a patient-reported diary that assesses respiratory symptoms in stable COPD.

METHODS

This post hoc analysis of a randomized, double-blind, parallel-arm trial (GSK ID: 200699; NCT02164539) assessed the structure, reliability, validity and responsiveness of the E-RS, and a separate wheeze item, for use in patients with a primary diagnosis of asthma or COPD, but with spirometric characteristics of both (fixed airflow obstruction and reversibility to salbutamol; a subset of patients referred to as spirometric asthma-COPD overlap [ACO]; N = 338).

RESULTS

Factor analysis demonstrated that E-RS included Cough and Sputum, Chest Symptoms, and Breathlessness domains, with a Total score suitable for quantifying overall respiratory symptoms (comparative fit index: 0.9), consistent with the structure shown in COPD. The wheeze item did not fit the model. Total and domain scores were internally consistent (Cronbach's alpha: 0.7-0.9) and reproducible (intra-class correlations > 0.7). Moderate correlations between RS-Total and RS-Breathlessness scores were observed with St George's Respiratory Questionnaire (SGRQ) Total and Activity domain scores at baseline (r = 0.43 and r = 0.48, respectively). E-RS scores were sensitive to change when a patient global impression of change and SGRQ change scores were used to define responders, with changes of ≥ - 1.4 in RS-Total score interpreted as clinically meaningful.

CONCLUSIONS

E-RS:COPD scores were reliable, valid and responsive in this sample, suggesting the measure may be suitable for evaluating the severity of respiratory symptoms and the effects of treatment in patients with asthma and COPD that exhibit spirometric characteristics of both fixed airflow obstruction and reversibility. Further study of this instrument and wheeze in new samples of patients with ACO is warranted.