Casemix and Diagnosis Related Group (DRG) Allocation – AR-DRG v7.0

DRG codes are calculated by the Ministry of Health. They are not reported to the National Minimum Dataset by hospitals.

The current DRG grouper is AR-DRG version 7.0, which uses up to 30 diagnoses and up to 30 procedures in its calculations. External cause codes are not used by the grouper. It is recommended that hospitals prioritise diagnoses and procedure codes within the current classification system in order to present the grouper with the most significant diagnoses and procedures.

The Ministry of Health groups all NMDS event records with an event end date on or after 1 July 2017 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 coded in ICD-10-AM/ACHI Eleventh Edition will have their codes back-mapped to ICD-10-AM/ACHI Eighth Edition which are then used to derive AR-DRG v7.0.

For further information about DRGs and Casemix rules refer to the New Zealand Casemix Framework for Publicly Funded Hospitals document available on the Weighted Inlier Equivalent Separations page.

Clinical coders are reminded that it is unacceptable to manipulate the Australian Coding Standards (ACS) and/or code assignment to optimise reimbursement/DRG or when trying to problem-solve an error DRG. Consultation with the Ministry of Health is important in order to maintain the integrity, consistency and accuracy of the data collection.

Below are the three Unrelated DRGs and the three Error DRGs from AR-DRG v7.0:

Unrelated DRGs

  • 801A OR Procedures Unrelated to Principal Diagnosis with Catastrophic CC
  • 801B OR Procedures Unrelated to Principal Diagnosis with Severe or Moderate CC
  • 801C OR Procedures Unrelated to Principal Diagnosis without CC

Error DRGs

  • 960Z Ungroupable
  • 961Z Unacceptable Principal Diagnosis
  • 963Z Neonatal Diagnosis Not Consistent W Age/Weight

For more information on AR-DRG v7.0 see Australia Refined Diagnosis Related Groups v7.0 (AR-DRGs v7.0).

If you have a case that has grouped to one of the six Unrelated/Error DRGs and you think the error may reflect a problem in the grouper logic, please contact the Ministry of Health via email: [email protected]

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