Each case identified by site study staff as potentially eligible for enrollment into the study will be entered into the case disposition log (CDL) and will be assigned a unique site-specific study identification number. These cases will be considered the study sampling frame. The SCC will select a preliminary target cohort of subjects from the sampling frame by selecting all e-SP cases and undertaking a random sample of NoP and BP cases within site to ensure 1:1:1 enrollment ratio between the 3 study groups. In the event that a sampling frame at a given site contains less NoP or BP cases when compared to e-SP cases, all NoP or BP cases will be selected for enrollment into the study and additional cases will be randomly selected from another site within the country to make up for the deficit if sampling frames allow. Sampling within site or alternatively within country ensures that NoP cases are matched to e-SP cases by lot of recalled PD solution. Cases within The Netherlands, Portugal and the UK all used the same recalled lot of PD solutions. Therefore, if within site and within country sampling cannot be achieved, across country sampling can be undertaken in these 3 countries. If it is determined that all e-SP and NoP cases in the sampling frame were on CAPD at the time of the index event, any BP cases identified in the sampling frame on APD at the time of index event may be excluded from the selection process (may not be selected to comprise the preliminary target cohort) and would therefore not be enrolled into the study.