Fig. 1

Reported problems in achieving national data collection in 28 European countries. Legend: Practical support refers to the need for more funding and staff to support data collection. Infrastructure includes regional not national datasets, and those countries where private and university hospitals are not linked, or respiratory and oncology hospitals that work independently. It also includes the absence of a single patient identifier, and also those countries without electronic transfer of data. Political will was stated by 1 co-author as was concern regarding legal requirements and issues of patient consent by a further 3 co-authors. Miscellaneous includes quite specific difficulties encountered in three countries. One co-author stated an historical lack of interest in epidemiology as a whole as a barrier to better data collection. Three languages are spoken in one country and in another, patients are often treated abroad, which makes evaluating treatment outcomes and follow-up very difficult. Seven countries stated there were no difficulties in collecting data at a national level