Published studies used several methods to assess the impact of lung transplantation on patient survival. To interpret the results of these studies, a basic understanding of the models used and underlying hypotheses is required.
The most often used method consists in assessing the survival of waiting-list patients and measuring the impact of lung transplantation on the baseline hazard (instantaneous risk) for death, usually with a Cox proportional hazards model. This strategy involves strong assumptions about the link between the baseline hazard in waiting-list patients and lung transplant recipients. Whether these assumptions are true is extremely difficult to establish. Some studies compared predicted survival without transplantation to observed survival after transplantation. We recently reported a new method in which predicted survival without transplantation is compared to predicted survival after transplantation.
All the methods described to date evaluate only the impact of transplantation on patient survival. The concomitant use of other markers such as respiratory function or quality of life would produce a more detailed picture of lung transplantation benefits.
Evaluating the benefits of lung transplantation involves the use of complex statistical methods. The results should be considered with circumspection, and none of the methods described to date allows definitive conclusions.Le texte complet de cet article est disponible en PDF.
Keywords : Biostatistics, Cox model, Survival analysis, Transplantation