Healthcare Quarterly

Healthcare Quarterly 1(3) March 1998 : 88-88.doi:10.12927/hcq..17377

Quarterly Index: Evaluating Changes in Practice with Resource Intensity Weights


Resource Intensity Weights (RIW) provide an estimate of the relative cost of resources used in the care of groups of similar patients. Comparable RIW values are calculated for inpatient (CMGTM)and day surgery groups (DPGTM) based on estimates of the expected length of stay and/or the costs of cases assigned to specific cells. As an indicator of resource use, RIWs represent a powerful tool for utilization management.
One resource management strategy that has been used to reduce hospital costs has been to shift traditional inpatient services to an ambulatory care setting. This trend can be clearly seen by comparing the growth in the number of lens insertions performed in an inpatient setting represented by CMG 55 (Lens Insertion) versus an ambulatory care1 setting represented by DPG 5 (Lens Procedures):

The above analysis clearly shows a decline in the overall volume of cases assigned to CMG 55 and a corresponding increase in the volume of cases assigned to DPG 5.

A similar pattern can be shown by province. The following graph illustrates the differential shift in service setting for this procedure for selected provinces submitting 100% of their data to CIHI over this period.

For 1996/97, 66% of uncomplicated cases in the DAD assigned to CMG 55 have a length of stay (LOS) of one day (see graph below). While not all cases with a one day stay could be treated in an ambulatory setting, the impact of moving even a small percentage of these cases to day surgery could significantly lower the resources required for lens insertion procedures.

RIW can be used as an estimate of the impact of shifting even 20% (535 cases) of the cases of one day length of stay to ambulatory care based on the total number of weighted cases in these cells. By multiplying the volume of inpatient cases by the corresponding RIW value for this CMG, the number of weighted cases is calculated. These same steps are done using the DPG RIW. The resulting resource burden for 535 cases assigned to DPG 5 and CMG 55 are as follows:

Inpatient Weighted Cases: 535 x .5936 = 317.58
Ambulatory Weighted Cases: 535 x .3882 = 207.69

In relative terms, moving these patients to an ambulatory setting increases efficiency of treatment by 35%.


Information for the Quarterly Index provided by the Canadian Institute for Health information (CIHI). For Information about CIHI or to access the Institute's publications please consult its website at For more information regarding these statistics please contact Warren Skea at (613) 241-7860 ext. 4042, or via email at


1. Hospital utilization data are from CIHI's Discharge Abstract Database (note: partial reporting for 96/97 from Saskatchewan, Manitoba, and Prince Edward Island does not include discharges from Quebec).


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