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Original Articles: Adult Cardiac

Using the National Death Index to Validate the Noninformative Censoring Assumption of Survival Estimation

Medical Data Research Center, Providence Health System, Portland, Oregon

Accepted for publication December 4, 2007.

^_* Address correspondence to Dr Wu, 9205 SW Barnes Rd, Ste 33, Portland, OR 97225 (Email: yingxing.wu{at}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.

This article has been cited by other articles:

				Y. Wu, J. J.M. Takkenberg, and G. L. Grunkemeier Measuring Follow-Up Completeness Ann. Thorac. Surg., April 1, 2008; 85(4): 1155 - 1157. [Abstract] [Full Text] [PDF]