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Updated: Jul 6, 2026

Inverse Probability of Treatment Weighting (Propensity Score) using the Military Health System Data Repository and National Death Index
Published on: January 8, 2020
Using the National Death Index to validate the noninformative censoring assumption of survival estimation
YingXing Wu1, Anthony P Furnary, Gary L Grunkemeier
1Medical Data Research Center, Providence Health System, Portland, Oregon, USA. yingxing.wu@providence.org
Background:
In survival analysis, a patient who is missing complete follow-up is included in the analysis as a censored observation. The analysis makes the assumption that the censoring is noninformative; that is, that a censored patient has the same risk of death as those who have complete follow-up. We tested this assumption in a large, long-term follow-up study.
Methods:
From 1986 through 2003, 14,495 patients underwent isolated coronary artery bypass grafting procedures. Of 13,963 eligible patients, 2312 were lost to follow-up. We obtained National Death Index data to complete our follow-up, and then compared survival between the original data and the complete National Death Index-augmented data.
Results:
The National Death Index data revealed 855 additional deaths and increased the total follow-up years from 86,810 to 102,157. Survival estimates and regression models did not differ between the original and National Death Index-augmented data.
Conclusions:
Patients lost to follow-up might not differ with regard to survival from those with complete data. The requirement for 95% completeness is somewhat arbitrary. The quality and type of follow-up is more important than the percentage in time-related analyses.
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