Assessment of a bronchodilator response in preschoolers: A systematic review

Abstract

Background: A bronchodilator response (BDR) can be assessed in preschool-aged children using spirometry, respiratory oscillometry, the interrupter technique, and specific airway resistance, yet a systematic comparison of BDR thresholds across studies has not been completed. Methods: A systematic review was performed on all studies up to May 2023 measuring a bronchodilator effect in children 2-6 years old using one of these techniques (PROSPERO CRD42021264659). Studies were identified using MEDLINE, Cochrane, EMBASE, CINAHL via EBSCO, Web of Science databases, and reference lists of relevant manuscripts. Results: Of 1224 screened studies, 43 were included. Over 85% were from predominantly Caucasian populations, and only 22 studies (51.2%) calculated a BDR cut-off based on a healthy control group. Sample sizes ranged from 25-916. Only two studies (4.6%) adhered to formal recommendations for study design: at least 300 subjects, randomised for placebo response testing in healthy children, and incorporated within-session and between-session test repeatability. A relative BDR was most consistently reported by the included studies (95%) but varied widely across all techniques. A variety of statistical methods were used to define a BDR. The highest BDR feasibility was reported with oscillometry techniques in this age group. Conclusion: A BDR in 2-6-year-olds cannot be defined based on the reviewed literature due to inconsistent methodology and cut-off calculations. Precise and feasible evaluation of lung function in young children is crucial for early detection and intervention of airway diseases. A standardised approach is required to develop robust BDR thresholds.