Over the course of the 18 month study, 6 observational assessments will take place. If the patient experiences a situation with increased inflammation during the study period (for example any kind of infection or intervention) up to two more study visits will take place. Each study visit will include blood sampling, performed without the need for an extra needle stick, and a breath sampling in order to calculate the red blood survival and to measure markers for inflammation in the blood. The breath sample will be taken using the easy to use GaSampler device developed by a company called Quintron especially for medical breath sampling.