Data references

Excel spreadsheet listing AR-DRG v10.0 MDCs and DRGs

From 1 July 2023 National Collections groups all National Minimum Dataset (NMDS) event records with an event end date on or after 1 July 2023 to AR-DRG v10.0.

AR-DRG v10.0 accepts ICD-10-AM/ACHI Eleventh Edition codes. ICD-10-AM/ACHI Eleventh Edition was used from 1 July 2019 until 30 June 2023.

ICD-10-AM/ACHI Twelfth Edition was implemented 1 July 2023. Event records clinically coded in ICD-10-AM/ACHI Twelfth Edition will have their codes back-mapped to ICD-10-AM/ACHI Eleventh Edition which are then used to group into AR-DRG v10.0.

AR-DRG v10.0 comprises 795 DRGs in 397 Adjacent DRGs (ADRGs). This compares with 771 DRGs in version 7.0 and 406 ADRGs.

AR-DRG v10.0 Format

The format of each AR-DRG v10.0 consists of four alphanumeric characters organised in terms of ‘MAAD’, where:

M – indicates the broad group (the MDC) to which the DRG belongs.

AA – identifies the adjacent DRG (ADRG) within the MDC and the partition to which the ADRG belongs. An ADRG consists of one or more DRGs generally defined by the same diagnosis or intervention codes. DRGs within an ADRG have differing levels of complexity, and are partitioned on the basis of several factors, including diagnoses/procedures used as a severity split, sameday, and level of comorbid disease and/or clinical complication.

The second and third characters (AA) identify the ADRG grouping and partition to which the ADRG belongs. These ranges are:

• 01 to 59 = to indicate the Intervention Partition
• 60 to 99 = to indicate the Medical Partition.

D – is a split indicator that ranks DRGs within an ADRG on the basis of their clinical complexity. The values are:

A = highest clinical complexity
B = second highest clinical complexity
C = third highest clinical complexity
D = fourth highest clinical complexity
Z = no split for the ADRG (ie, no subgroups).

Major Diagnostic Categories (MDCs)

The MDC is a category generally based on a single body system or aetiology that is associated with a particular health specialty. MDCs are assigned according to the principal diagnosis. In AR-DRG v10.0 there are 23 MDCs and one Pre MDC.

Episode Clinical Complexity (ECC)

The Episode Clinical Complexity model was introduced in AR-DRG v8.0 and has continued to be refined in later AR-DRG classification systems. The new ECC model was introduced for determining clinical complexity. The ECC model assigns diagnosis complexity level (DCL) weights and episode clinical complexity scores (ECCS). The episode clinical complexity scores quantify relative levels of resource utilisation within each ADRG and are used to split ADRGs into DRGs on the basis of resource homogeneity.

The ECCS determines the final DRG to which an episode of care is assigned within an ADRG.

An ECCS is an output from the grouper software and is a value between 0 and 32 with decimals of .5 (eg, 21.5)

The complexity terms listed are used in the naming of DRGs where an episode clinical complexity score has been used as a splitting variable:

• Minor complexity
• Intermediate complexity
• Major complexity
• Extreme complexity.

Further information about the ECC model and ECCS derivations is available on the IHACPA AR-DRG Version 10.0 webpage.

Excel spreadsheet listing AR-DRG v7.0 MDCs and DRGs

From 1 July 2017 to 30 June 2023 National Collections grouped all National Minimum Dataset (NMDS) event records to AR-DRG v7.0.

AR-DRG v7.0 accepts ICD-10-AM/ACHI Eighth Edition codes. ICD-10-AM/ACHI Eighth Edition was used from 1 July 2014 until 30 June 2019.

ICD-10-AM/ACHI Eleventh Edition was implemented 1 July 2019. Event records clinically coded in Eleventh Edition had their codes back-mapped to ICD-10-AM/ACHI Eighth Edition, which were used to group into AR-DRG v7.0.

AR-DRG v7.0 comprises 771 DRGs in 406 Adjacent DRGs (ADRGs). This compares with 708 DRGs in version 6.0x and 399 ADRGs. Reflecting changes in clinical practices, most of the new DRGs in v7.0 are for same day episodes of care.

AR-DRG v7.0 Format

The format of each AR-DRG v7.0 consists of four alphanumeric characters organised in terms of ‘MAAD’, where:

M – indicates the broad group (the MDC) to which the DRG belongs.

AA – identifies the adjacent DRG (ADRG) within the MDC and the partition to which the ADRG belongs. An ADRG consists of one or more DRGs generally defined by the same diagnosis or procedure code list. DRGs within an ADRG have differing levels of resource consumption, and are partitioned on the basis of several factors, including diagnoses/procedures used as a severity split, sameday, and level of comorbid disease and/or clinical complication.

The second and third characters (AA) identify the ADRG grouping and partition to which the ADRG belongs. These ranges are:

• 01 to 39 = surgical
• 40 to 59 = other
• 60 to 99 = medical.

D – is a split indicator that ranks DRGs within an ADRG on the basis of their consumption of resources. The values are:

A = highest consumption of resources
B = second highest consumption of resources
C = third highest consumption of resources
D = fourth highest consumption of resources
Z = no split for the adjacent DRG (ie, no subgroups).

Major Diagnostic Categories (MDCs)

The MDC is a category generally based on a single body system or aetiology that is associated with a particular health specialty. MDCs are assigned according to the principal diagnosis. In AR-DRG v7.0 there are 23 MDCs and one Pre MDC.

Patient Clinical Complexity Level (PCCL)

Patient clinical complexity level is a measure of the cumulative effect of a patient’s complications and/or comorbidities (CC), and are calculated for each episode. PCCL values are:

• 0 = no CC effect
• 1 = minor CC
• 2 = moderate CC
• 3 = severe CC
• 4 = catastrophic CC.

The PCCL calculation is complex and has been designed to prevent similar conditions from being counted more than once during the grouping process.  A detailed explanation of the PCCL algorithm is in Appendix C of the AR-DRG v7.0 Definitions Manual, Volume 3.

(Source: Independent Health and Aged Care Pricing Authority: AR-DRG v7.0 Definitions Manual 2013)

Excel spreadsheet listing AR-DRG v6.0x MDCs and DRGs

From 1 July 2013 to 30 June 2017 National Collections grouped all National Minimum Dataset (NMDS) event records to AR-DRG v6.0x.

AR-DRG v6.0x accepts ICD-10-AM/ACHI Sixth Edition codes. ICD-10-AM/ACHI Eighth Edition was implemented 1 July 2014. Event records clinically coded in Eighth Edition had their codes back-mapped to ICD-10-AM/ACHI Sixth Edition, which were used to group into AR-DRG v6.0x.

AR-DRG v6.0x comprises 708 DRGs in 399 Adjacent DRGs (ADRGs).

AR-DRG v6.0x Format

The format of each AR-DRG v6.0x consists of four alphanumeric characters organised in terms of ‘ADDS’, where:

A – indicates the broad group to which the DRG belongs (MDC).

DD – identifies the adjacent DRG (ADRG) within the MDC and the partition to which the ADRG belongs. An ADRG consists of one or more DRGs generally defined by the same diagnosis or procedure code list. DRGs within an ADRG have differing levels of resource consumption, and are partitioned on the basis of several factors, including diagnoses/procedures used as a severity split, sameday, and level of comorbid disease and/or clinical complication.

The second and third characters (DD) identify the ADRG grouping and partition to which the ADRG belongs. These ranges are:

• 01 to 39 = surgical
• 40 to 59 = other
• 60 to 99 = medical.

S – is a split indicator that ranks DRGs within an ADRG on the basis of their consumption of resources. The values are:

A = highest consumption of resources
B = second highest consumption of resources
C = third highest consumption of resources
D = fourth highest consumption of resources
Z = no split for the adjacent DRG (ie, no subgroups).

Major Diagnostic Categories (MDCs)

The MDC is a category generally based on a single body system or aetiology that is associated with a particular health specialty. In AR-DRG v7.0 there are 23 MDCs and one Pre MDC.

Patient Clinical Complexity Level (PCCL)

Patient clinical complexity level is a measure of the cumulative effect of a patient’s complications and/or comorbidities (CC), and are calculated for each episode. PCCL values are:

• 0 = no CC effect
• 1 = minor CC
• 2 = moderate CC
• 3 = severe CC
• 4 = catastrophic CC.

The PCCL calculation is complex and has been designed to prevent similar conditions from being counted more than once during the grouping process.  A detailed explanation of the PCCL algorithm is in Appendix C of the AR-DRG v6.0 Definitions Manual, Volume 3.

(Source: Independent Health and Aged Care Pricing Authority: AR-DRG v6.0 Definitions Manual 2008)

New Zealand Casemix Framework Document WIESNZ25 v1.0 December 2024 Tracked Changes (DOCX, 911KB)

New Zealand Casemix Framework Document WIESNZ25 v1.0 December 2024 Clean Copy (DOCX, 889KB)

This year is a major change year involving the upgrade to ICD-10-AM/ACHI Twelfth Edition, the new DRG version AR-DRG v11.0, review of NZ DRGs, co-payments and a full new set of weights for implementation from 1 July 2025. 

Exclusion rules are based on ICD-10-AM/ACHI Twelfth Edition clinical coding and AR-DRG v11.0.

WIESNZ25 includes the following changes from the previous year: 

·         ICD-10-AM/ACHI diagnosis and procedure codes including descriptors updated to 12th Edition

·         DRGs and descriptors updated to AR-DRG v11.0

·         Revised NZ DRG Allocation

o   Updated NZ DRG B02W Stroke Clot Retrieval to B08W Other Stroke Clot Interventions including the rule for NZ DRG allocation

·         Revised DRGs in section DRGs Excluded from Mechanical Ventilation Days

·         Revised co-payment definitions and values for:

o   Abdominal Aortic Aneurysm (AAA)

o   Spinal Fusion (SF)

o   Electrophysiological Studies (EPS)

o   Bilateral Mastectomy or Combined Mastectomy and Reconstruction (MR)

o   Gender Reaffirming Surgery (GR)

o   Peritonectomy with HIPEC (PH)

·         Revised co-payment values for:

o   Live Donor Nephrectomy (LDN)

o   Ventricular Assist Device (VAD) for Adults

o   Complex Traumatic Limb (TLC)

o   Cardiac Lead Extraction (LE)

o   Pelvic Evisceration (PE) Surgery

o   Neurostimulator (NS) 

·         Revised exclusion rules for:

o   Same Day Pharmacotherapy for Prophylaxis or Treatment of Neoplasm

o   Lithotripsy

o   Colposcopies

o   Same Day Transrectal Ultrasound (TRUS) Guided Biopsy of Prostate and Transperineal (TPA) Biopsy of Prostate

·         Revised Disability and Health of Older People

·         Revised various sections from 5 Purchase Unit Allocation

·         Added new Section 5.4 Mapping of Health Specialty Codes to Non-Casemix Purchase Units

·         Updated all Appendices.

During the financial year updates to the framework may be required for example, a problem is found with one of the rules or a facility is approved for inclusion to the WIES facilities eligible list. Updates will be documented at the start of the Casemix Framework document under section 'Version Updates to Casemix Framework Document'.

New Zealand Casemix Framework For Publicly Funded Hospitals (WIESNZ24) Tracked Changes v1.2 20 March 2024

New Zealand Casemix Framework For Publicly Funded Hospitals (WIESNZ24) v1.5 4 October  2024

WIESNZ24 is based on ICD-10-AM/ACHI Eleventh Edition and AR-DRG v10.0.

NMDS event records clinically coded in ICD-10-AM/ACHI Twelfth Edition will have their codes back-mapped to ICD-10-AM/ACHI Eleventh Edition which are then used to derive AR-DRG10.0.

Exclusion rules are based on ICD-10-AM/ACHI Eleventh Edition clinical coding and AR-DRG v10.0. The framework associated with WIESNZ24 is the same as WIESNZ23 except for the following:

• Revised NZ DRG Allocation
  • Updated NZ DRG R64W
• New Co-payment for Neurostimulator (NS)
• Revised co-payment definitions and values for:
  • Abdominal Aortic Aneurysm (AAA)
  • Electrophysiological Studies (EPS)
  • Cardiac Lead Extraction (LE)
  • Peritonectomy with HIPEC (PH)
• Revised co-payment values for:
  • Spinal Fusion (SF)
  • Live Donor Nephrectomy (LDN)
  • Ventricular Assist Device (VAD) for Adults
  • Complex Traumatic Limb (TLC)
  • Bilateral Mastectomy or Combined Mastectomy and Reconstruction (MR)
  • Gender Reaffirming Surgery (GR)
  • Pelvic Evisceration (PE) Surgery
• New exclusion rules for:
  • Same Day Intravenous Drug Infusions (MS02029)
  • Same Day Intravenous Gamma Globulin Infusions (MS03010)
• Revised exclusion rules for:
  • Transplants
  • Radiotherapy
  • Hysteroscopy
• Revised DRG Mapping and Exclusion of Skin Lesion Procedures
• Revised Disability and Health of Older People.

During the financial year updates to the framework may be required for example, a problem is found with one of the rules or a facility is approved for inclusion to the WIES facilities eligible list. Updates will be documented at the start of the Casemix Framework document under section 'Version Updates to Casemix Framework Document'.

New Zealand Casemix Framework For Publicly Funded Hospitals (WIESNZ23) v1.4 25 September 2024

WIESNZ23 is based on the classifications ICD-10-AM/ACHI Eleventh Edition and AR-DRG v10.0.

NMDS event records clinically coded in ICD-10-AM/ACHI Twelfth Edition will have their codes back-mapped to ICD-10-AM/ACHI Eleventh Edition which are then used to derive AR-DRG v10.0.  

Exclusion rules are based on ICD-10-AM/ACHI Eleventh Edition clinical coding and AR-DRG v10.0.  The framework associated with WIESNZ23 is the same as WIESNZ22 except for the following:

• ICD-10-AM/ACHI diagnosis and procedure codes including descriptions updated to Eleventh Edition
• DRGs and descriptions updated to AR-DRG v10.0
• New and revised same day/one day designations
• Revised NZ DRG Allocation
  • Deleted NZ DRG F03M
  • Updated NZ DRG B02W
  • Updated the code for the NZ DRG O66T to O66W
• Deleted co-payment for Atrial Septal Defect (ASD)
• Revised co-payment definitions and values for:
  • Abdominal Aortic Aneurysm (AAA)
  • Scoliosis (SCOL) renamed to Spinal Fusion (SF)
  • Electrophysiological Studies (EPS)
  • Live Donor Nephrectomy (LDN)
  • Ventricular Assist Device (VAD) for Adults
  • Complex Traumatic Limb (TLC)
  • Bilateral Mastectomy or Combined Mastectomy and Reconstruction (MR)
  • Gender Reaffirming Surgery (GR)
  • Peritonectomy with HIPEC (PH)
  • Pelvic Evisceration (PE) Surgery
• Revised co-payment value for:
  • Cardiac Lead Extraction (LE)
• Revised exclusion rules for:
  • Medical termination of pregnancy
  • Same day pharmacotherapy for treatment of neoplasm
  • Colposcopies
  • Gastroenterology procedures
  • Bronchoscopies
  • Same Day Transrectal Ultrasound (TRUS) Guided Biopsy of Prostate and Transperineal (TPA) Biopsy of Prostate
• Revised DRG Mapping and Exclusion of Ophthalmology Injections
• Revised excluded purchase unit codes for:
  • Peritoneal Dialysis
  • Same Day Radiotherapy
• Added new facilities Franklin Private Hospital (9300) and Waitemata Endoscopy (9080) to the casemix eligible facilities list.

During the financial year updates to the framework may be required for example, a problem is found with one of the rules or a facility is approved for inclusion to the WIES facilities eligible list. Updates are documented at the start of the Casemix Framework document under section 'Version Updates to Casemix Framework Document'.

New Zealand Casemix Framework For Publicly Funded Hospitals (WIESNZ22) v1.4 August 2023

WIESNZ22 is based on the classifications ICD-10-AM/ACHI Eighth Edition and AR-DRG v7.0.

NMDS event records clinically coded in ICD-10-AM/ACHI Eleventh Edition will have their codes back-mapped to ICD-10-AM/ACH Eighth Edition which are then used to derive AR-DRG v7.0. Exclusion rules are based on ICD-10-AM/ACHI Eighth Edition coding and AR-DRG v7.0. 

This WIESNZ22 version includes the following changes from the previous year:

• Removed section ‘Special Funding Arrangement for Temporomandibular Joint Replacement (TMJ)’
• Revised Scoliosis co-payment definition
• Revised Live Donor Nephrectomy (LDN) co-payment value
• Revised Ventricular Assist Devices (VADs) for Adults co-payment definition and value
• Revised Gender Reaffirming Surgery (GR) definition
• Revised patient’s age to be calculated at time of admission
• Revised Disability and Health of Older People exclusion rule
• Revised excluded purchase unit code for Postnatal Early Intervention
• Added new excluded purchase unit code for Same Day Radiotherapy
• Revised anaesthesia criteria to include sedation on two exclusion rules
• Added new facilities Southern Cross Central Lakes Hospital (9297), South Island Plastic Surgery (9311), Mr Terrace Creagh (9312), Face Breast and Body (9313) and OneSixOne (9271), Franklin Private Hospital (9300) and Waitemata Endoscopy (9080) to the casemix eligible facilities list.

New Zealand Casemix Framework For Publicly Funded Hospitals (WIESNZ21) v1.4

WIESNZ21 is based on the classifications ICD-10-AM/ACHI Eighth Edition and AR-DRG v7.0.

NMDS event records clinically coded in ICD-10-AM/ACHI Eleventh Edition will have their codes back-mapped to ICD-10-AM/ACH Eighth Edition which are then used to derive AR-DRG v7.0.  Exclusion rules are based on ICD-10-AM/ACHI Eighth Edition coding and AR-DRG v7.0. 

This WIESNZ21 version includes the following changes from the previous year:

• New and revised same day/one day designations
• Revised co-payment definitions:
  • Aortic Aneurysm (AAA) co-payment
  • Scoliosis
  • Electrophysiological Studies (EPS)
  • Complex Traumatic Limb (TLC)
  • Gender Affirming Surgery (GR)
• Reinstated co-payment for Isolated Limb Infusion (ILI)
• New co-payment for:
  • Peritonectomy with HIPEC (PH)
  • Pelvic Evisceration (PE) Surgery for Waitemata DHB
• Revised co-payment values for:
  • Atrial Septal Defect (ASD)
  • Ventricular Assist Devices (LVAD)
  • Bilateral Mastectomy or Combined Mastectomy and Reconstruction
  • Cardiac Lead Extraction (LE)
• Revised costweight values for NZ DRGs C03W and J11W
• Moved section ‘Note on anaesthesia coding’ to be sequenced before exclusion rules that have an anaesthesia criteria
• Revised exclusion rules:
  • Same day pharmacotherapy for treatment of neoplasm
  • ERCP
  • Cystoscopies
  • Gastroscopy procedures
  • Bronchoscopy
• Added new facilities to the casemix eligible facilities list. The facilities are Rutherford Clinic (9245), East Bay Specialist Centre (9283), Cambridge Specialist Centre (9284), Southern Cross Central Lakes Hospital (9297), South Island Plastic Surgery (9311), Mr Terrace Creagh (9312), Face Breast and Body (9313) and OneSixOne (9271)
• Added DRGs P07Z and P08Z to the Neonatal Inpatient Casemix (W06.03) rule
• Updated exclusion rules Cystoscopies and Bronchoscopies so the second procedure did not include GA. Changed wording from ‘block [1910] codes’ to ‘sedation codes’ as per the third procedure.

New Zealand Casemix Framework For Publicly Funded Hospitals (WIESNZ20) v1.2

WIESNZ20 is based on the classifications ICD-10-AM/ACHI Eighth Edition and AR-DRG v7.0.

NMDS event records clinically coded in ICD-10-AM/ACHI Eleventh Edition will have their codes back-mapped to ICD-10-AM/ACH Eighth Edition which are then used to derive AR-DRG v7.0.  Exclusion rules are based on ICD-10-AM/ACHI Eighth Edition coding and AR-DRG v7.0. 

This WIESNZ20 version includes the following changes from the previous year:

• Revised definition of the NZ DRG B02W for stroke clot retrieval
• Retired co-payment for isolated limb infusion
• New co-payments for:
  • Gender affirming surgery
  • Cardiac lead extraction
• Revised co-payment values for:
  • Abdominal aortic aneurysm (AAA)
  • Atrial septal defect (ASD)
  • Scoliosis
  • Live donor nephrectomy
  • Ventricular assist devices (VADs)
  • Complex traumatic limb cases
  • Bilateral mastectomy or combined mastectomy and reconstruction
• Revised bilateral mastectomy or combined mastectomy and reconstruction co-payment to include DRG J14Z
• New exclusion rule for transrectal ultrasound (TRUS) guided biopsy of prostate and transperineal (TPA) biopsy of prostate
• Revised exclusion rules:
  • Rhesus isoimmunisation and other isoimmunisation
  • Renal haemodialysis
  • Same day radiotherapy
• New health specialty code S44 Orthopaedic spinal surgery
• Health specialty code P39 Maternal Fetal Medicine (MFM) Services added to the NMDS. Previously valid for NNPAC reporting only
• Added Appendix 8: ICD-10-AM/ACHI Mapping Table
• Added new facilities to the casemix eligible facilities list. The facilities are Hamilton Radiology (9225), The Rutherford Clinic (9245), East Bay Specialist Centre (9283) and Cambridge Specialist Centre (9284).