- A realistic data set will be fundamental to the success of the investigation, and this was confirmed in the EuSOS study where nearly complete data was available on 46 000 patients. We have therefore adopted the EuSOS dataset with minor changes following advice from the EuSOS steering committee, and believe that these key data points will not discourage centres from participating because of an excessive burden of data collection. The reliability of data collection will be analysed formally using K-statistics or intra-class correlation coefficients as appropriate.