20 March 2025
Chris Johnston
[FYI request #28619 email] Tēnā koe Chris,
Your request for official information, reference: HNZ00079974
Thank you for your email on 20 February 2025, asking Health New Zealand | Te Whatu Ora for the
following under the Official Information Act 1982 (the Act):
1) Does HealthNZ systems record the number of people in NZ hospitals presenting with
Chest pain or heart issues for the years 2017 to 2024 in any form? Which system(s)
collects and stores these and are they stored against an NHI number? State the coding
scheme used (eg ICD-10, DRGs)
2) Does HealthNZ systems record the number of people in NZ hospitals diagnosed with
Chest pain or heart issues for the years 2017 to 2024 in any form? State the coding
scheme used (eg ICD-10, DRGs)? Indicate which of these systems store the NHI
number (or a hashed/obscured version of it).
3) From which systems are HealthNZ able to collate Age Ranges of those attending NZ
Hospitals - particularly for the following categories - under 40, 40 to 65 inclusive, over
65? Indicate which of these systems store the NHI number (or a hashed/obscured
version of it).
4) From which systems are HealthNZ able to collate Doses of COVID vaccines (
0,1,2,3,4,5,6,7+)? Indicate which of these systems store the NHI number (or a
hashed/obscured version of it).
5) Where a person had multiple visits to an Emergency Dept in a year please confirm that
these are able to be identified and in which HealthNZ systems. Indicate which of these
systems store the NHI number (or a hashed/obscured version of it).
6) Please confirm that HealthNZ recruit and employ information analysts that are able to:
a) Count rows in a database, and also distinct values in a column (eg NHI numbers, or
their hashed/obscured equivalent).
b) Link tables together via inner or outer joins if required based on the NHI number or its
hashed/obscured equivalent.
c) Confirm that analysts with the required skills above do have access to the systems
outlined in the questions 1 to 5 above.
If the responses to the questions above confirm that a dataset is available, then please:
7) Proceed with the original OIA request, suitably amending any typos or inadvertent mis-
speak on my part that led HealthNZ to believe that it could not fulfil the OIA request
because the data did not exist. For example:
- HealthNZ may have interpreted my mentioning of NHI as a field that was not available
because it was encrypted but actually the hashed/obscured value serves the same
purpose); OR
- There may be a debate about the terms and coding schemes or field for "presenting"
vs "diagnosed" and I am happy for presenting to be reinterpreted as diagnosed IF this is
the cause of your rejection AND it enables the dataset to be generated.
b) Explain which aspect of the information requested in the OIA is not available as
stated in your letter of the 19 Feb 2025.
For clarity, my understanding was that the HealthNZ systems:
- Record and store for each hospital event ICD or DRG codes, health provider, NHI (or
hashed equivalent), date of the event
- Record and store for every vaccination (especially for COVID) the NHI (or
hashed/obscured equivalent), date of event and relevant coding to identify the product,
batchID, and product type (eg COVID vaccine).
- Record and store for every person in the NHI system (used to be PerOrg) - the NHI
number or hashed/obscured equivalent, and the date of birth (from which age range
can be calculated at the point an event occurs).
- Data warehouse and surveillance/analytical platforms that bring all of the above
together using IDs such as the NHI (or its hashed/obscured equivalents) for reporting
and insight purposes.
Please confirm that my understanding of (8) is correct or explain in what way this
understanding is not incorrect?
Response
For clarity, I have responded to each part of your request in turn.
1) Does HealthNZ systems record the number of people in NZ hospitals presenting
with Chest pain or heart issues for the years 2017 to 2024 in any form? Which
system(s) collects and stores these and are they stored against an NHI
number? State the coding scheme used (eg ICD-10, DRGs)
Health New Zealand holds the National Minimum Dataset (NMDS) which records information about
all publicly and any privately funded hospital events. The data is based on information from the
treating hospitals, which is reported to Health NZ to collate into a national dataset.
NMDS used ICD-10-AM codes to indicate the condition which caused the admission (primary
diagnosis), and some secondary diagnosis information. In most cases the secondary diagnosis
information relates not to the symptoms that were presenting, but what the clinician concluded was
causing them.
NHI number is reported on the records from the treating hospitals, and collated into the NMDS.
Health NZ also holds the National Non-Admitted Patient Collection (NNPAC) which records
information about outpatient events provided in hospitals, including Emergency Department (ED)
attendances. This data is based on information reported by hospitals to Health NZ to collate into a
national dataset. In 2019, the coding system Systematized Medical Nomenclature for Medicine–
Clinical Terminology (SNOMED) was added to NNPAC data for the Chief Presenting Complaint. All
hospitals were reporting SNOMED codes in 2024.
SNOMED coding was the source of the information provided for HNZ00078687.
At present SNOMED coding is not implemented across all hospitals in a consistent manner.
Additionally, there are no analytical frames for aggregating the thousands of terms reported – ie to
put a set of SNOMED codes into one group of similar conditions. As such, SNOMED coding
information is currently unsuitable for detailed analysis.
NHI number is reported on the records from the treating hospitals and collated into NNPAC.
2) Does HealthNZ systems record the number of people in NZ hospitals diagnosed
with Chest pain or heart issues for the years 2017 to 2024 in any form? State the
coding scheme used (eg ICD-10, DRGs)? Indicate which of these systems store
the NHI number (or a hashed/obscured version of it).
See response above re coding of diagnostic information in NMDS and NNPAC data. This is the
data held nationally by HNZ for hospital events.
3) From which systems are HealthNZ able to collate Age Ranges of those attending
NZ Hospitals - particularly for the following categories - under 40, 40 to 65 inclusive,
over 65? Indicate which of these systems store the NHI number (or a
hashed/obscured version of it).
NMDS and NNPAC both record an age on the record submitted to Health NZ.
4) From which systems are HealthNZ able to collate Doses of COVID vaccines (
0,1,2,3,4,5,6,7+)? Indicate which of these systems store the NHI number (or a
hashed/obscured version of it).
Health NZ uses the Aotearoa Immunisation Register (AIR) which records information about most
publicly funded vaccines provided in New Zealand. The data is based on records of immunisations
given by a number of health providers, including primary care providers and pharmacists. The AIR
includes information about COVID vaccinations given.
The AIR includes the NHI number of the person receiving the vaccine.
5) Where a person had multiple visits to an Emergency Dept in a year please confirm
that these are able to be identified and in which HealthNZ systems. Indicate which
of these systems store the NHI number (or a hashed/obscured version of it).
NNPAC collects ED attendances, and includes NHI information.
6) Please confirm that HealthNZ recruit and employ information analysts that are able
to:
c) Count rows in a database, and also distinct values in a column (eg NHI numbers, or
their hashed/obscured equivalent).
Yes.
d) Link tables together via inner or outer joins if required based on the NHI number or its
hashed/obscured equivalent.
Yes. This linking is difficult and time consuming, the time required depends on the specifics of the
data requested.
c) Confirm that analysts with the required skills above do have access to the systems
outlined in the questions 1 to 5 above.
Analytical teams across HNZ have access to different datasets depending on the team in which
they work, and the area of focus for that team.
Using and linking databases together requires the analyst to have in-depth knowledge of the data
collections which they are linking, and an understanding of how errors could arise if the data were
analysed incorrectly. This is complex analytical work, which takes time and resource.
Complex analysis amounts to creation of information and not covered by the Act. Health NZ is
legally required to provide data which we hold, but is not required to create new information for OIA
responses. In this instance, linking the requisite data together to respond to your request would
amount to having to create new information through the application of complex skill and judgement.
7) If the responses to the questions above confirm that a dataset is available, then please:
a) Proceed with the original OIA request, suitably amending any typos or inadvertent mis-
speak on my part that led HealthNZ to believe that it could not fulfil the OIA request
because the data did not exist. For example:
- HealthNZ may have interpreted my mentioning of NHI as a field that was not available
because it was encrypted but actually the hashed/obscured value serves the same
purpose); OR
- There may be a debate about the terms and coding schemes or field for "presenting" vs
"diagnosed" and I am happy for presenting to be reinterpreted as diagnosed IF this is the
cause of your rejection AND it enables the dataset to be generated.
b) Explain which aspect of the information requested in the OIA is not available as stated in
your letter of the 19 Feb 2025.
8) For clarity, my understanding was that the HealthNZ systems:
- Record and store for each hospital event ICD or DRG codes, health provider, NHI (or
hashed equivalent), date of the event
- Record and store for every vaccination (especially for COVID) the NHI (or
hashed/obscured equivalent), date of event and relevant coding to identify the product,
batchID, and product type (eg COVID vaccine).
- Record and store for every person in the NHI system (used to be PerOrg) - the NHI
number or hashed/obscured equivalent, and the date of birth (from which age range can be
calculated at the point an event occurs).
- Data warehouse and surveillance/analytical platforms that bring all of the above together
using IDs such as the NHI (or its hashed/obscured equivalents) for reporting and insight
purposes.
Please confirm that my understanding of (8) is correct or explain in what way this
understanding is not incorrect?
Our responses to questions 1-6 cover off these questions. The data you are requesting is not one
existing dataset, it would require linking several disparate datasets together and requires in-depth
knowledge of the contributing datasets.
The information you have requested is complex analytical research, and providing this type of
analysis amounts to creation of information under the Act (refer to section 18(g)).
How to get in touch
If you have any questions, you can contact us at
[email address].
If you are not happy with this response, you have the right to make a complaint to the
Ombudsman. Information about how to do this is available at
www.ombudsman.parliament.nz or
by phoning 0800 802 602.
As this information may be of interest to other members of the public, Health NZ may proactively
release a copy of this response on our website. All requester data, including your name and
contact details, will be removed prior to release.
Nāku iti noa, nā
Danielle Coe
Manager (OIAs) – Government Services
Health New Zealand | Te Whatu Ora
TeWhatuOra.govt.nz
Health NZ, PO Box 793,
Wellington 6140, New Zealand
