How representative are clinical trial cohorts of the general CF population? Implications for trial planning

•Restrictive eligibility criteria lead to non-representative cohorts of patients participating in research and reduce the numbers of patients available to take part in trials.•We audited our clinic population to identify what percentage of our cohort meet the common trial eligibility criteria and to ascertain the most frequent reason(s) for trial ineligibility.•Only 31 % of our total population and 23 % of our modulator ineligible (MI) cohort meet the common eligibility criteria.•The most common reason for ineligibility in both groups was having a ppFEV1 higher than the 90 % cut-off.•Using novel endpoints may allow the inclusion of patients with better lung functions and be the most effective way to increase the number of patients available to take part in trials.