NHI number format change: Public comment document

Comments are invited on the content, wording and format/usefulness of the proposed change to this standard.

Please use the template below to record your comments. Be sure to quote the relevant paragraph number. Include a reason for any change or you propose. Unfortunately, we cannot accept marked-up copies of the document itself.

In your submission, please clearly identity yourself and the organisation (if any) that you are representing.

Submissions should be emailed to by 14 November 2017.

A working group will consider all submissions and agree on any changes to the document. Further public comment is expected to be sought before a final decision is made.

Note:this draft is released for public comment only. It is not a published document.

General Comment
Paragraph number / Comment
Submitted by:
Name:
Organisation:
  1. Proposed change to NHI number format:

Background

  1. The National Health Index System and its included National Health Index number (NHI number)[1] has been in place for more than 20 years. It is the primary system used to uniquely identify an individual to enable matching of that individual’s demographic data with health information.
  2. The National Health Index has assigned the majority of the currently available NHI range. At current rates of allocation there are sufficient available NHI numbers for another 8 to 9 years. All existing NHI numbers are forecast to be exhausted around 2025.[2]
  3. NHI numbers are used pervasively throughout the health and disability sector and systems are designed for a seven digit sequence. Because the identifier is used so widely and in so many systems there will be a significant programme of change required to update systems to use a new number format. It is important that this change is signalled early to provide the sector with sufficient lead time to investigate and implement any required changes.

Considerations

  1. Several options have been considered. These include removing or changing the check digit sum, moving to an extended character number sequence, or reconfiguring the current seven character number sequence. Each has its advantages and disadvantages.
  2. While the use of manually inputted NHIs will decrease over time, it is still likely that NHIs will be used in a manual form either on written forms, manually entered, spoken over communication systems like telephone or transmitted by analogue (and therefore degradable) technology such as facsimile for many years to come. The check digit remains an important feature to reduce the chances of transposition and transcription errors in these circumstances.
  3. Any change to the NHI check-digit algorithm will require changes to the underlying source code in systems.
  4. Any change to the NHI length will require changes to the underlying source code in systems as well as the underlying databases and user-interfaces that hold that data. Database and user-interface changes to accommodate a change in NHI length would be a substantial and large piece of work.
  5. Basic changes to the format that substitute numeric and alpha characters are unlikely to require a change in most databases.
  6. For the reasons above it would be hugely disruptive to move to an ‘internationally unique’ format such as that used by the Australian Individual Healthcare Identifier (IHI).[3] In any case, the NHI represents an identifier in the NZ health system and global healthcare identifier standards remain immature.
  7. Additionally, the recommend option must not preclude the future linking of NHI numbers to RealMe verified identities to facilitate an individual’s transactions with the health system (e.g. General Practice enrolment).

Recommended option

  1. The recommended option is to change the check digit algorithm and number format within the existing NHI identifier length of 7 characters, from AAANNNN to AAANNAA. The cutover would occur once the existing number range is exhausted and the old format would be retained alongside the new format. No mapping between NHI numbers would be required.
  2. This option will minimise the impact on sector systems (i.e. it can be contained within the same space and within the same database field size as the existing identifier), maintains a similar look to existing identifier, and reduces the potential for issuing NHI numbers containing offensive expressions.
  3. The check-digit would be changed to an alphabetic character based on a modulus 24 operation to eliminate existing transposition problems with the modulus 11 operation.
  4. The “Z” range of numbers will be reserved as test identifiers.
  5. Under this proposal and at current allocation rates there would be sufficient NHI numbers to last another 130 years.

[1]The NHI number is an alpha-numeric identifier in the format of AAANNNN, where A is an alpha character and N is a numeric. The last character is a modulus 11 check digit.

[2] This assumes that the Z range of NHI numbers will be reserved for testing purposes.

[3]The IHI is a 16 digit number sequence. Digits N1-N6 represent the “issuer identification number” which includes the industry identifier, country code, and number type.