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What Does Case Mix Mean in Home Health?

by Keith Grunig

Home Health Case Mix Questions Image

Case Mix Weight Explained

A lot is said about case mix, but there really isn't a lot published about Case Mix and what it actually means, and even further, what does it mean in the home health context.  National Association of Home Care and Hospice (NAHC) has a small explainer of key terms in home health.  NAHC defines it as “Case Mix—term used to identify resource use for Medicare providers. For Medicare home health, certain M items indicate clinical severity, functional status and service utilization and determine the case mix score.” You can access the link to that definition (here).  

There are many terms that are thrown around such as Case Mix, HHRG, and HIPPS.  In reality, these terms are all basically the same thing.  They are representations in various forms of how sick a person is.  Case Mix, is a numerical term that represents the condition of a patient.  In general, CMS uses the number 1 as a typical home health patient. If the patient is a little less sick (or more functional) the number could go down.  If a patient is sicker (or less functional), then the number will be higher.  The numbers are not large fluctuations.  Think of it as standard deviation, or deviation from the mean in math terms.  Most of the time, the number will be fairly close to 1.  

Home Care Answers has built a PDGM calculator that shows each patient's case mix.  I will explain below why case mix matters to agencies below. 

Case Mix Changes from PDGM to PPS

CMS outlined changes on how case mix would be scored with PPS going away and PDGM replacing it as the reimbursement model.  Most notably, therapy utilization is no longer part of the reimbursement calculation.  There are a few other changes, but we will write another post about that as it is more technical than an overview of case mix.  You can read about the changes here.

Case Mix- Why does it matter?

CMS tracks all the data that agencies provide back to them through OASIS assessments.  Agencies provide all the ammunition needed for CMS to enact changes.  The change from PPS to PDGM was driven, and validated, by the data that agencies gave them.  Who should we blame for the difficulties wrought by PDGM?  Well, look no further than in the mirror.  Agencies gave the data that fueled the change and chaos of PDGM.  Therapy utilization, compared to case mix weights, was often too high.  If a patient is more or fully independent based on the case mix derived from OASIS, then why is so much therapy given?  Well, in PPS days, it was to drive revenue.  Therapy overutilization as a means for reimbursement was a significant driver to PDGM coming along.  

Case mix matters a lot.  The case mix is a representation of how sick, functional, or independent a given patient is.  That is also tied to reimbursement.  The sicker or less functional the patient, the more reimbursement given.  It's really that simple.   

Case Mix Corrected

At Home Care Answers, we find that, most of the time, patients are sicker and/or less independent that the patient wants to admit, or the clinician assesses the patient through OASIS assessments.  In your minds' eye, imagine a patient.  The patient is a 78-year-old female who has Parkinson's disease, dementia starting to manifest, diabetes, history of smoking, and lives alone but has a daughter who comes regularly to help the patient. and recently had a hip replacement.  The patient is referred to home health and is seated in her living room chair when the clinician arrives.  The patient is already dressed in sweat pants when the nurse arrives.  The nurse starts the OASIS and asks if the patient has pain.  "No, I feel very good and don't have any pain."  The clinician marks zero on OASIS.  The med log shows opioids and the nurse documents that the patient had recently taken pain meds according to the doctor's instruction.  The nurse then gets to the ADL section of OASIS and notices that the patient is already dressed.  The nurse asks can you dress yourself?  The patient answers "I got dressed this morning."  The clinician marks that the patient can independently dress the lower body.  In fact, as the nurse asks additional questions about the ADLs (activities of daily living) the patient responds that she is fine and can do it.  The nurse doesn't ask the patient to demonstrate any of these actions or activities.  Therapists want to have 10 visits to help the patient improve balance and gait training.   Upon completion of OASIS, the home health agency does the coding, omits Parkinson's as a diagnosis, and completes the OASIS and submits with the signed plan of care.  The case mix on the patient is .987 based on the OASIS.  Home Care Answers then reviews the chart and notices some inconsistencies in the diagnosis, documentation, and the OASIS.  Home Care Answers corrects the coding to include Parkinson's.  Upon review of the ADL section, we notice that the patient was completely dressed in sweat pants.  But given the fact that the patient just had a hip replacement and shouldn't bend the hip more than 45 degrees.  With Parkinson's and dementia, and with the hip replacement, the patient has some imbalance issues.  Just because the patient did everything independently doesn't mean the patient SHOULD and is doing it safely.  Likely, the patient shouldn't shower independently, dress the lower body independently, and certainly should not get up and down out of bed or the chair alone.  After our review and suggested changes to the OASIS and coding, the patient now has a case mix of 1.069.  That is an increase of .0883 in case mix.  

Why does this matter?  Prior to the OASIS and coding corrections, under PDGM, the agency would be reimbursed $3,623.  After our suggested changes and coding, the agency will now be reimbursed $3,944.54.  That is $320.80 more than the agency would have been reimbursed or a 7.716% increase.   

At Home Care Answers, we can tell you what the case mix is, what the change is, and show why it matters.  In the example above, those are actually the average case mix weights of all patients we have reviewed since January 1, 2020.  We have reporting to show each agency the value and change in case mix that we help them discover and we create.  Here is what it is below.  Note, we've been able to help agencies find an additional $8,089,560.63 of additional reimbursement that would have been left on the table.  But more importantly, it gives CMS accurate data on which to base decisions and changes for future tweaks to PDGM.  


Prior Total $91,380,026.91
New Total $99,469,587.54
Prior Average $3,623.75
New Average $3,944.54
Average Prior Case Mix 0.9796
Average Case Mix 1.0652
Average Case Mix Gain 0.0856
Total Gain $8,089,560.63
Average Gain $320.80
Percent Gained 7.716%

We show this important information for each patient we review also.  It shows PDGM information before/after auditing, HIPPS code, Case Mix Summary and other important for each patient in a simple report.


We want to help you get OASIS correct.  Many agencies just send the OASIS down the river and move on.  But what about discharge?  If the patient shows on paper as independent, but clearly isn't, then how will the patient show improvement upon discharge?  This affects quality measures also.  Most of the time, patients do improve from the great work that agencies do.  But it is often not recorded on OASIS at the beginning of the episode, and therefore cannot be documented at discharge.  That's too bad and the agency loses out.  When everything is said and done, it is essential for OASIS to be correct.  When OASIS is correct, revenue follows.  Outcomes follow.  Compliance follows.  




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