Elixhauser Comorbidity Index was developed as part of the Healthcare Cost and Utilization Project (HCUP).  It’s sponsored by the Agency for Healthcare Research and Quality and is utilized by U.S. News and World Reports Best Hospitals as a method of categorizing comorbidities.  Elixhauser Comorbidity Index predicts resource allocation, assesses the quality of care, and risk adjusts patient models.  

The Elixhauser Comorbidity Indexes Refined for ICD-10-CM are designed to predict two frequently reported health outcomes: risk of in-hospital mortality and/or risk of 30-day, all-cause readmission. Because the scores are different for each comorbidity measure in the two indices, the facility must decide which comorbidity index they wish to calculate. For example, the Comorbidity Measure of ‘Diabetes with chronic complications’ can have two scores depending on the selected index; the AHRQ Mortality weight (score) is 4, while the AHRQ Readm weight (score) is negative 2. 

So how do you locate and determine Elixhauser scores?  The accurate coding of secondary diagnoses and POA assignment is key, coupled with grouping software.   The Elixhauser comorbidity software refined for ICD-10-CM “creates comorbidity measures that identify pre-existing medical conditions that are not directly related to the main reason for the hospital encounter and that, if present on admission, would be associated with a substantial impact on certain outcomes, such as an increase in length of stay, charges, or in-hospital mortality.”

There are 38 comorbidity measures that are identified using 4,417 secondary ICD-10-CM diagnoses along with the appropriate POA indicator on an inpatient discharge or outpatient record. Twenty of the thirty-eight comorbidity measures do not require the use of POA indicators because the condition can be assumed to be pre-existing and not the result of hospital care. The remaining 18 comorbidity measures must have a POA indicator of YES to be calculated.  Individual diagnosis codes may be assigned to more than one comorbidity measure in the Elixhauser Comorbidity Software Refined for ICD-10-CM - In v2023.1, there are 120 out of 4,417 ICD-10-CM diagnosis codes that are included in more than one comorbidity measure.

Example: If a secondary diagnosis code of I50.33, Acute on chronic diastolic (congestive) heart failure occurred after the patient was in the hospital, the diagnosis will not trigger the comorbidity measure for heart failure (CMR_HF). The software requires the condition be present on admission.

Example: If a secondary diagnosis code of K25.4, Chronic or unspecified gastric ulcer with hemorrhage is not present on admission because the hemorrhaging occurred after the patient was in the hospital, the diagnosis will not trigger the comorbidity measure for peptic ulcer with bleeding (ULCER_PEPTIC). The software requires the condition be present on admission.

In brief summary, even though secondary diagnoses may not impact DRG/SOI/ROM, they could affect the Elixhauser score.  What are the three fundaments instrumental for accurate capture of Elixhauser data?  1) Obtain knowledge of the comorbidity indexes and corresponding diagnoses.   2) Team up with HIM coders and auditors to capture the most accurate diagnoses and present on admission indicators to calculate the correct score.  As always, each record should be reviewed independently and coded in accordance with the ICD-10-CM Official Coding Guidelines.   3) Have the appropriate grouping software is an integral piece that will enhance and simplify the process of calculating scores.   

Kristi Landry, RHIA, CCS, CDIP

Manager, Consulting

Reference: https://hcup-us.ahrq.gov/toolssoftware/comorbidityicd10/comorbidity_icd10.jsp