The impact of the loss to follow-up when using the Kaplan Meier estimator and the Cox proportional hazard model / Avaliação do efeito das perdas de seguimento nas análises feitas pelo estimador produto - limite de Kaplan - Meier e pelo modelo de riscos proporcionais de Cox
AUTOR(ES)
Marcia Moreira Holcman
DATA DE PUBLICAÇÃO
2006
RESUMO
Introduction: The Kaplan Meier product limit estimator (KM) and the Cox proportional hazard (HR) model are the most used tools in survival analysis. These two methods have the key assumption that censoring must be independent from the survival time. Objective: To analyze the consequences of loss to follow up in these two methods. Methods: The study has utilized the data of the Cancer Registry of the patients of Hospital do Cancer in São Paulo of 1994. The informative censure was simulated transforming the death by 5 to 50% into alive. Besides 5 to 50% was spared at random simulating the non-informative censoring. The survival probability and was calculated to the first, third and fifth year of follow up. All the estimated probabilities and HRs were compared with the results of the original data. Results: Patients with greater scholars, lower stages and admitted by health plans or private had more losses to follow up. The maximum proportion of accepted loss to follow up is 10% to 15% when using the KM estimator, and the HR are less affected by the loss to follow-up and one can afford having 20% of it. When the losses were non informative there were no differences between the original probabilities. Conclusions: The possibility of over or under estimated probability must be analyzed in the presence of the losses to follow- up when using the KM and HR in survival analyses.
ASSUNTO(S)
cox proportional hazard model kaplan-meier análise de sobrevida kaplan-meier survival analysis modelo de cox perda de seguimento loss to follow-up
