Mortality ascertainment of participants in the National Wilms Tumor Study using the National Death Index: comparison of active and passive follow-up results

Table 1 NDI* match counts by January 1, 2002 vital status as ascertained in April 2005

	January 1, 2002 vital status ascertained in April, 2005 from NWTS* records
	Dead				Alive		Unknown		Total (%)
NDI*	1970–1978		1979–2001
Match	0		709		0		18		727	(11.7)
No Match	198		80		1,052		2,333		3,663	(58.9)
Not sent	0		0		1,826		1†		1,827	(29.4)
Total (%)	198	(3.2)	789	(12.7)	2,878	(46.3)	2,352	(37.8)	6,217	(100.0)

* NDI, National Death Index; NWTS, National Wilms Tumor Study.
† Record not sent to the NDI due to an error in date last seen which was later corrected