Frequently Asked Questions

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How reliable is Medicaid Covered Inpatient Days in the MAX Inpatient Hospital (IP) data?

Medicaid Covered Inpatient Days from MAX IP records should be used with caution.  In many cases, the Medicaid Covered Inpatient Days data element accurately reflects Length of Stay (LOS), but in some cases Medicaid covered Inpatient Days can be an inaccurate measure of LOS.  Here are some selected examples:

  • Medicaid Covered Inpatient Days are set to zero for IP crossover records (claims for which both Medicare and Medicaid make payments) for dual Medicare and Medicaid enrollees.  This is because Medicare is the first payer.  Medicaid pays for only copayment and deductible amounts, as applicable.
  • MSIS instructions for Medicaid Covered Inpatient Days state that, if the claim is a combined mother/newborn claim, the days should include both the days for the mother and the newborn.  In this instance, the count of covered days could exceed the number of days from beginning to ending dates of service.  Also, there would be no easy way to separate days for the mother from days for the newborn.
  • For IP records whose Medicaid Covered Inpatient Days data element value is greater than 365, the data element value is recoded to 365.  This could occur for very long stays.


For these and other reasons, the claims adjustment process may cause the Medicaid Covered Inpatient Days data element to have a value that is inconsistent with the beginning and ending dates of service.   To determine LOS, researchers are urged to calculate the value instead of using Medicaid Covered Inpatient Days.  The most accurate calculation is to count the number of days from the beginning date of service to the ending date of service plus one day.  There should be no inpatient hospital stays with LOS = 0.  If a patient was admitted and discharged on the same day, LOS = 1.


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