Systematic review and meta-analysis on cold air bronchial challenge test for asthma diagnosis

BACKGROUND: Asthma is a heterogeneous disease, making uniform diagnosis challenging, resulting in both under- and overdiagnosis. We conducted a systematic review and meta-analysis to summarise the data on diagnostic accuracy of a cold air bronchial challenge test (CACh) in exercise-induced bronchoconstriction and asthma. METHODS: Databases (PubMed, Embase, Web of Science core collection, Cochrane Library and the Cumulative Index to Nursing and Allied Health Literature EBSCO) were systematically screened for articles evaluating the use of CACh as a diagnostic tool in exercise-induced bronchoconstriction and asthma. A random-effects model was used to calculate the effect on the reduction in forced expiratory volume in 1 s (FEV) by CACh in healthy controls compared to patients with asthma. Risk of bias was evaluated using the Quality Assessment of Diagnostic Accuracy Studies-Comparative. This study is registered with PROSPERO (www.crd.york.ac.uk/PROSPERO/ identifier number CRD42021290350). RESULTS: After screening and removal of duplicates, 39 studies were included. Aggregate sensitivity and specificity of a FEV decrease ≥10% after CACh were 0.808 and 0.959, respectively. The weighted mean difference in percentage FEV decrease after CACh for patients with asthma compared to healthy controls was -17.58. High heterogeneity (I=99) was mainly explained by differences in reference tests to diagnose asthma. Application of the trim-and-fill method to account for publication bias imputed eight studies, resulting in a notable reduction in heterogeneity. The overall effect (a significant decrease in FEV in patients with asthma) remained statistically significant (-8.18, p<0.001). CONCLUSION: Our study shows the high sensitivity and specificity and possible clinical implications of a CACh in the diagnosis of asthma. Further research is needed to confirm this.