The COPD Assessment Test: what have we learned over its first 5 years?

It is 5 years since the development and first validation of the COPD Assessment Test (CAT) [1], so the review of papers concerning the CAT by GUPTA et al. [2] in this issue of the European Respiratory Journal is very timely. The authors identified over 40 studies using a systematic approach to minimise biases, although they acknowledge that they introduced one bias by selecting papers published only in English, French and Spanish, so eight papers were excluded. That may not be too problematic, as the included papers report data on over 25 000 patients from 35 countries across five continents (none from Australasia or Antarctica).