Reliability and Minimum Important Difference of Sputum Weight in Bronchiectasis

Abstract

BACKGROUND: Despite the widespread use of sputum weight to assess the effect of airway clearance interventions, its psychometric properties have not been evaluated. The purpose of this ad hoc analysis was to determine the test-retest reliability of 24-h sputum weight in clinically stable individuals with bronchiectasis. This study also aimed to estimate the minimum important difference of 24-h sputum weight after an airway clearance session in subjects with bronchiectasis. METHODS: Sixty subjects were included in the 24-h test-retest cohort, 42 of whom were part of the airway clearance cohort. For the 24-h test-retest cohort, spontaneously expectorated sputum was collected over 24 h on 2 different days without any airway clearance interventions. For the airway clearance cohort, sputum expectoration was also collected during 3 airway clearance sessions and over the 24 h following these interventions. Intraclass correlation coefficient (ICC 3,1) and Bland-Altman analysis were used to assess reliability. The minimum important difference was calculated using distribution-based and anchor-based methods, with cough impact as assessed with the Leicester Cough Questionnaire and the global rating of change as anchors. RESULTS: The reliability was acceptable (ICC 3,1 5 0.75) for sputum weight over 24 h without any intervention. The agreement level was wide, particularly for high levels of sputum expectoration. The minimum important difference of the sputum collected in the 24 h after the intervention from baseline was 26.4 g (about 217%), determined using distributionbased methods. There was no correlation between sputum weight and the anchors, thus the anchor-based methodology could not be used. CONCLUSIONS: Multiple measurements should be considered to increase the agreement when sputum weight is used as an outcome measure for short periods in people with bronchiectasis. A reduction of 6.4 g (or 17% from baseline) in sputum collected during the 24 h after the airway clearance intervention may be considered the minimum important difference in people with bronchiectasis. (ClinicalTrials.gov registration NCT02392663; NCT01854788; NCT02614300.

Reliability and Validity of Computerized Adventitious Respiratory Sounds in People with Bronchiectasis

“…The limits of agreement were quite wide for all parameters, particularly in the between-day analysis; the only exception was when the average of the crackles did not exceed seven. Therefore, the use of repeat measurements may be a good solution to improve the dispersion around the mean, as previously was reported for other outcome measures [25,47]. Overall, SEM and SDC values tend to be high for all ARS parameters, particularly in the between-days analysis, as it was expected.…”

“…Sociodemographic data (age, gender) and chronic respiratory medication were reported by the participants in the first session. Lung function (forced spirometry) [24], sputum volume collected in the containers (average of 24 h sputum volume obtained in the two previous days) [25], the impact of coughing (Leicester Cough Questionnaire, LCQ) [26], quality of life (quality of life-bronchiectasis, QoL-B) [27] and dyspnea (MRC Breathlessness Score) [28] were also assessed at the beginning of the first session. Disease severity was calculated using the Bronchiectasis Severity Index (BSI) [29].…”

European Respiratory Society statement on airway clearance techniques in adults with bronchiectasis

“…Following other interventions in bronchiectasis, these studies should incorporate long term follow up, i.e., not less than three months for PROMs and not less than six months for exacerbations, hospitalisations or cost-effectiveness. Although sputum quantity is the most frequent outcome measure selected as primary outcome in ACTs trials in bronchiectasis, its measurement properties are ambiguous [122]; thus, its interpretation is still unclear [123]. Future trials should incorporate more robust measures, such as exacerbation frequency, hospital admission and patient-reported outcomes, particularly validated diseasespecific questionnaires that have a clear interpretation [124,125].…”

Active cycle of breathing technique versus oscillating PEP therapy versus walking with huffing during an acute exacerbation of bronchiectasis: a randomised, controlled trial protocol

“…Twenty-four-hour sputum volume has been shown to be a responsive outcome measure during acute exacerbations of bronchiectasis [ 29 , 43 , 45 ]. Either an increase in sputum volume during the session, or one-hour post-session, or a decrease in sputum volume in the following 24-h period will be interpreted as an improvement in sputum clearance [ 29 , 30 , 43 ].…”

“…The goal of ACBT and O-PEP therapy is to facilitate secretion removal, therefore an improvement in sputum removal would correspond with an increase in sputum expectorated during or immediately following an airway clearance session, plus or minus a decrease in sputum expectoration in the 24 h following an airway clearance session [17,29,30]. A recent international guideline also recommended implementation of the ACBT or O-PEP therapy for individuals with stable bronchiectasis (level D-low level evidence), based on current evidence available [12].…”