Average case mix indexes determined quarterly — Facility average case mix index — Medicaid average case mix index.
RCW 74.46.501
in effect(1) From individual case mix weights for the applicable quarter, the department shall determine two average case mix indexes for each medicaid nursing facility, one for all residents in the facility, known as the facility average case mix index, and one for medicaid residents, known as the medicaid average case mix index. (2)(a) In calculating a facility's two average case mix indexes for each quarter, the department shall include all residents or medicaid residents, as applicable, who were physically in the facility during the quarter in question based on the resident assessment instrument completed by the facility and the requirements and limitations for the instrument's completion and transmission (January 1st through March 31st, April 1st through June 30th, July 1st through September 30th, or October 1st through December 31st). (b) The facility average case mix index shall exclude all default cases as defined in this chapter. However, the medicaid average case mix index shall include all default cases. (3) Both the facility average and the medicaid average case mix indexes shall be determined by multiplying the case mix weight of each resident, or each medicaid resident, as applicable, by the number of days, as defined in this section and as applicable, the resident was at each particular case mix classification or group, and then averaging. (4) In determining the number of days a resident is classified into a particular case mix group, the department shall determine a start date for calculating case mix grouping periods as specified by rule. (5) The cut-off date for the department to use resident assessment data, for the purposes of calculating both the facility average and the medicaid average case mix indexes, and for establishing and updating a facility's direct care component rate, shall be one month and one day after the end of the quarter for which the resident assessment data applies. (6) Although the facility average and the medicaid average case mix indexes shall both be calculated quarterly, the cost-rebasing period facility average case mix index will be used throughout the applicable cost-rebasing period in combination with cost report data as specified by RCW 74.46.561 , to establish a facility's allowable cost per case mix unit. A facility's medicaid average case mix index shall be used to update a nursing facility's direct care component rate semiannually.
(1) From individual case mix weights for the applicable quarter, the department shall determine two average case mix indexes for each medicaid nursing facility, one for all residents in the facility, known as the facility average case mix index, and one for medicaid residents, known as the medicaid average case mix index.
(2)(a) In calculating a facility's two average case mix indexes for each quarter, the department shall include all residents or medicaid residents, as applicable, who were physically in the facility during the quarter in question based on the resident assessment instrument completed by the facility and the requirements and limitations for the instrument's completion and transmission (January 1st through March 31st, April 1st through June 30th, July 1st through September 30th, or October 1st through December 31st).
(b) The facility average case mix index shall exclude all default cases as defined in this chapter. However, the medicaid average case mix index shall include all default cases.
(3) Both the facility average and the medicaid average case mix indexes shall be determined by multiplying the case mix weight of each resident, or each medicaid resident, as applicable, by the number of days, as defined in this section and as applicable, the resident was at each particular case mix classification or group, and then averaging.
(4) In determining the number of days a resident is classified into a particular case mix group, the department shall determine a start date for calculating case mix grouping periods as specified by rule.
(5) The cut-off date for the department to use resident assessment data, for the purposes of calculating both the facility average and the medicaid average case mix indexes, and for establishing and updating a facility's direct care component rate, shall be one month and one day after the end of the quarter for which the resident assessment data applies.
(6) Although the facility average and the medicaid average case mix indexes shall both be calculated quarterly, the cost-rebasing period facility average case mix index will be used throughout the applicable cost-rebasing period in combination with cost report data as specified by RCW 74.46.561 , to establish a facility's allowable cost per case mix unit. A facility's medicaid average case mix index shall be used to update a nursing facility's direct care component rate semiannually.
Source: WA Statutes (Official Site)URL: https://app.leg.wa.gov/RCW/default.aspx?cite=74.46&full=trueFetched: 6/29/2026