Beginning with 2019, Arizona uses a different masking method. The coding of Medical Record Number is not consistent with prior years.

There are no discharge records with the same MRN from 2017-2018.

Beginning in 2017, CO supplies an MRN field that has been encrypted by a built-in function in SQL called "Always Encrypted". According to a data contact, the MRN field was converted via "Deterministic" method (not "Randomized"), so you should be able to match a single patient's multiple records looking up the same MRN even if encrypted.

In 2004, Colorado changed their encryption routine for Medical Record Number.

In 2003, the Colorado Medical Record Number coding scheme changed; therefore, it cannot be used to track patients consistently before and after 2003.

The Hawaii medical record number (MRN_R) cannot be used to track patients consistently over time from 2003 to 2004. Hawaii provides a re-identification medical record number. Hawaii reported that there were problems with the consistent assignment of the re-identified MRNs in 2004. Beginning with 2005, the patient should retain the same re-identification number across years, which permits readmission studies from 2005 forward.

Prior to 2002, Hawaii encrypted their medical record numbers using an algorithm unique to the data organization. There is slight variation in the assignment of encrypted medical record number across years prior to 2002 due to differences in handling non-numeric characters each year and other variations of this sort. Nonetheless, the patient retains the same identification number up through 2001, which allows for readmission studies within years and longitudinal analysis across years through 2001.

Iowa reports encrypted medical record numbers.

Caution should be used when using MRN_S to track patients back to 1999. The values supplied by the data source in the 1999 data appear different from the values supplied beginning in 2000.

Maine provides encrypted medical record numbers. During HCUP processing, medical record numbers were re-encrypted (MRN_R).

The format of encrypted medical record number (MRN_R) is inconsistent across years.

• Prior to 1993, the medical record number was supplied with no padding of the values.
• Beginning in 1993, the supplied medical record number included padding that was retained in the encrypted values.

Beginning in Q4 of 2015 the source values changed. Therefore, MRN_R is not consistent with data from prior years.

In 2018 the source values changed; therefore, they are not consistent with data from 2014-2017.

In 2014 the source values changed; therefore, they are not consistent with data from previous years.

Prior to the 2010 data year, mothers' medical record numbers were encrypted using a specific encryption routine that is different from the routine used to encrypt medical record numbers. Because of the use of different encryption routines for these two fields, values in the MOMNUM_R field do not match the values in MRN_R field.

Beginning in 2008 the source values changed; therefore, they are not consistent with data from previous years.

Again in 2010, the source values changed and they are not consistent with previous years.