Table 1. Distribution of NPI-UPIN matches identified by three independent approaches and the level of across-approach agreement, for physician NPIs identified in the 2007-2008 SEER-Medicare claims data.

Within-approach NPI-UPIN match					Across-approach agreement+
Approach 1: SEER-Medicare claims	Approach 2: NPI Directory: listed UPIN	Approach 3: NPI and UPIN Directories: listed names	N (Total=470,313)	% of NPIs	All	Two	One source only	Unresolvable Conflicts++
YES	YES	YES	224,557	47.8	219,315	5,179		63
YES	YES	NO	45,392	9.7		44,681		711
YES	NO	YES	49,927	10.6		49,044		883
NO	YES	YES	63,860	13.6		61,373		2487
YES	NO	NO	11,887	2.5			11,816	71
NO	YES	NO	16,148	3.4			16,015	133
NO	NO	YES	16,760	3.6			16,419	341
NO	NO	NO	41,782	8.9

NPI: National Provider Identifier; SEER: Surveillance, Epidemiology, End Results; UPIN: Unique Physician Identification Number

⁺Among matches that were identified within at least 2 approaches.

⁺⁺Unresolvable conflicts defined as >1 NPI to 1 UPIN or 1 NPI to >1UPIN