Q&A: A GMLOS primer

Q: I’ve heard that the geometric length of stay (GMLOS) is always rounded to the nearest whole number as inpatient claims are paid by day. Based on my understanding of the inpatient prospective payment system (IPPS), I thought that each inpatient stay is paid by a fixed amount, regardless of the number of days the patient is in the hospital. Can you clarify this for me? Also, are there any cases when the GMLOS wouldn’t be rounded to the closest whole number?

A: You’re correct that under the IPPS, each hospital encounter is paid a specific amount of money per encounter, which is calculated using the relative weight (RW) of each MS-DRG (no matter where you work, the RW for each MS-DRG will be the same). The relative weight is then multiplied by the hospital’s base rate (which varies from facility to facility; the national base rate for 2021 is $5891.33). This is a simplified answer as other things are taken into consideration when determining a hospital’s reimbursement for an inpatient stay, such as how the facility performs on certain quality programs, whether they are a teaching hospital, or the facilities location.

As for your question regarding payment by days or episode of care, let’s look at an example. Let’s just assume that, based on the documentation in the medical record, the patient had a principal diagnosis that led to the assignment of MS-DRG 179, Respiratory infection and inflammation without a CC/MCC. This MS-DRG has a length of stay of about 4.0 days and a RW of 0.8711. To answer the question of payment we would take the RW and multiply it by the hospital’s base rate, which would give us a total reimbursement of approximately $5,131.93 with a GMLOS of 4.0 days. So, what all this means is that the facility will be paid a little over five thousand dollars for approximately four days of care for this patient.

I can further determine what the payment per day would be by dividing the total payment for this encounter by the number of days which we calculate rounding up the GMLOS. This number is always rounded up to simplify—againthere is a lot more detail that goes into this. Based on the information provided I have a pretty good idea what the payment should be per day, $1,282.98 per/day for four days.

Using the GMLOS as a guide I can then determine when this patient should be discharged (generally speaking).If the person is hospitalized longer than the estimated four days, you can see that with each additional day the payment to the hospital becomes less per day. For example, if this person is hospitalized six days the hospital still receives the $5,131.93 (unless something occurs like a surgical procedure that would change the discharge DRG) but, now it has to cover six days of care versus the original four days dropping the rate from $1,282.98 to $855.32 per/day. This payment must cover all care provided by the facility including room and board. The only thing not covered is physician care.

To recap, if the patient goes home in less than four days the amount of payment per day would increase, or if they stay longer than the average four days, it would decrease per day, or if the patient is transferred to another facility, then the reimbursement could change completely, based on whether or not the discharge DRG is a transfer DRG. Based on this information, the hospital could cover their cost for taking care of this patient or lose money based on a patient’s length of stay and what tests are performed or what care is provided during the patient’s stay.

I want to stress that much more goes into these calculations to determine how much a facility would be paid then simply what is covered in this example. As a CDI specialist, you will establish the “working” MS-DRG for a patient. This working MS-DRG will give you the GMLOS. This GMLOS is generally what the CDI specialist will use to determine their review schedule for the patient’s medical record.

For example, I know if a person has a four-day GMLOS, I can probably wait 24-48 hours to do my initial review, giving the physician a chance to evaluate any testing the patient may have undergone. If the patient only has a three or fewer days expected GMLOS, I know I need to perform my initial review sooner.

Knowing the GMLOS for an encounter would also trigger a CDI specialist to question when a person is not discharged when expected, which could indicate that a follow-up review is necessary. 

Remember, a CDI specialist’s job is to make sure the documentation is present in the medical record to support the appropriate principal diagnosis assignment, secondary diagnoses, and any procedures performed during the patient’s stay. Accurate documentation will lead to an appropriately assigned MS-DRG, which will include the appropriate expected LOS for that patient.

Editor’s Note: Sharme Brodie, RN, CCDS, CCDS-O, CDI education specialist and CDI Boot Camp instructor for HCPro in Middleton, Massachusetts, answered this question. For information, contact her at sbrodie@hcpro.com. For information regarding CDI Boot Camps, click here. This article was originally published in August 2019 and has been updated according to all new coding and documentation guidelines.