WIESNZ20 cost weights

Documentation and a cost weight table for the WIESNZ20 methodology.


The New Zealand Casemix Framework for Publicly Funded Hospitals provides the definitions for inclusion of hospital events in casemix funding together with information related to the calculation of cost weights for these events and the assignment of events to purchase units. WIESNZ20 is based on ICD-10-AM/ACHI Eighth Edition and AR-DRG v7.0.

ICD-10-AM/ACHI Eleventh Edition was implemented 1 July 2019.  Events 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-DRG7.0. Exclusion rules are based on ICD-10-AM/ACHI Eighth Edition coding and AR-DRG v7.0.  The framework associated with WIESNZ20 is the same as WIESNZ19 except for the following:

  • 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 facility 9225 Hamilton Radiology to the casemix eligible facilities list
  • Added Appendix 8: ICD-10-AM/ACHI Mapping Table
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