Record Identifier Variables (RXRECIDX, LINKIDX, DRUGIDX. The variable RXRECIDX uniquely identifies each record on the file. This 15-character variable comprises the following components: prescribed medicine drug-round-level identifier generated through the HC (positions 1-12) + enumeration number (positions 13-15). The prescribed medicine drug-round-level ID generated through the HC (positions 1-12) can be used to link a prescribed medicine event to the conditions file and to other event files, via link files, and is provided on this file as the variable LINKIDX. For more details on linking, please refer to Section 6.2 and to the 2016 Appendix File. The prescribed medicine drug-level ID generated through the HC, DRUGIDX, can be used to link drugs across rounds. DRUGIDX was first added to the file for 2009; for 1996 through 2008, the RXNDC linked drugs across rounds. The following hypothetical example illustrates the structure of these ID variables. This example illustrates a person in Rounds 1 and 2 of the household interview who reported having purchased Amoxicillin three times. The following example shows three acquisition-level records, all having the same DRUGIDX (00002026002), for one person (DUPERSID=00002026) in two rounds. Generally, within a round, one NDC is associated with a prescribed medicine event because matching was performed at a drug level, as opposed to an acquisition level. The LINKIDX (000020260083) remains the same for both records in Round 1 but varies across rounds. The RXRECIDX (000020260083001, 000020260083002, 000020260103001) differs for all three records. DUPERSID PURCHRD RXRECIDX LINKIDX DRUGIDX RXNDC 00002026 1 000020260083001 000020260083 00002026002 00093310905 00002026 1 000020260083002 000020260083 00002026002 00093310905 00002026 2 000020260103001 000020260103 00002026002 00003010955 There can be multiple RXNDCs for a LINKIDX. All the acquisitions in the LINKIDX represent the same drug (active ingredients), but the RXNDCs may represent different manufacturers. (For more details on matching, please see Section 4.0).
