Q&A: Elixhauser comorbidities
Q: What are Elixhauser comorbidities, and how does present on admission (POA) status, clinical significance, and sequencing play a role in reporting them?
A: Elixhauser comorbidities are a set of 38 categories mapped through ICD-10 codes, and each comorbidity is assigned a score or a weight that is used to help predict the overall risk of inpatient hospital mortality for a particular condition. There are some conditions that are highly associated with in-house mortality and others that are not likely to lead to mortality. A good example is metastatic cancer, one of the highest weighted conditions that is associated with mortality for in-house deaths, unlike depression that does not have a high correlation with hospital deaths. When listed as secondary diagnoses, usually present on admission (POA), they will represent a patient’s risk adjustment, which includes resource allocation, length of stay, or outcome predictions like hospital mortality and readmission.
Some conditions are listed twice as a comorbidity such as for hypertension, with a comorbidity for complicated hypertension and another for uncomplicated hypertension. Only one can be listed and ideally it will be complicated hypertension since it has a higher weight associated with it. This situation of having multiple Elixhauser comorbidities also applies to diabetes and liver disease. However, Elixhauser comorbidities are not considered diagnoses themselves. For example, weight loss is an Elixhauser comorbidity but not a diagnosis, although there are ICD-10 diagnosis codes mapped to the condition like malnutrition or cachexia. Claiming any of the diagnosis codes that map to an Elixhauser comorbidity is how the comorbidity is reported.
Most of the comorbidities require POA status, and in instances that the status is not required, it is usually because there is some sort of presumption already included in the Elixhauser methodology. For example, AIDS or cancer do not develop during hospital encounters so no matter what the POA status is, the Elixhauser methodology automatically gives credit for it. For most of the comorbidities, however, reporting them as POA is necessary to get credit for it. Eighteen of the 38 comorbidities are dependent on the POA indicator.
Some key considerations coding teams should keep in mind to ensure accuracy is to first educate themselves on the importance of reporting these conditions with accurate POA statuses. When it comes to making sure the diagnosis is reportable, coders need to verify the condition is documented and meets clinical significance based on guidelines. Codes cannot be added if they aren’t significant to the patient's stay, specifically meeting the Uniform Hospital Discharge Data Set (UHDDS) definition for reporting additional diagnoses.
Thrombocytopenia is an Elixhauser comorbidity that can be identified when the platelet count is abnormal, but proving its clinical significance is where coders have to leverage critical thinking and build a strong query. Signs to look for include increased bleeding (nosebleeds, bleeding gums, gastrointestinal bleed), procedure delays because platelets were not in normal range, or adjustments to medication due to abnormal platelets counts. Sometimes coders might have to do a little more digging to make their queries stronger, and they will need to make sure that the clinical notes can support a compliant query for the condition.
For some Elixhauser comorbidities, it is likely internal definitions and thresholds will need to be determined. Going back to cachexia, this condition falls under the comorbidity for weight loss within the Elixhauser where the POA indicator does matter. Providers will often describe patients as being cachectic, but coders will need to determine whether it is clinically supported and how did the condition impact care for the patient. A less stringent definition for cachexia may include some sort of muscle loss and chronic metabolic condition, and it could be expanded to include recent weight loss. The muscle wasting and presence of a metabolic condition would still be key, yet it is a definition that teams may go back and forth on. Having internal guidelines to follow and providing examples of when to query so that both coding and CDI teams are on the same page with the condition can be helpful. Go through that diagnosis list on the comorbidity mapping to see where there are opportunities for reporting improvements.
For medically complicated patients, there may easily be 50 or 60 diagnosis codes for patients that were actively treated during their particular stay, though most claims have a limit of up to 25 diagnosis codes. It can be a challenge to determine the best sequence of a large number of codes. Let’s say metastatic cancer dropped below the first 25 codes for a patient. This would be a huge opportunity to sequence it higher given its weight, otherwise it essentially doesn’t count if it is listed below the first 25 codes. Coding teams should be fully aware of the importance of some of these conditions. Luckily some Elixhauser comorbidities can represent multiple conditions, so only one condition would need to be sequenced closer to the top, such as obesity, which can represent both obesity and body mass index. Doing this type of sequencing would require a diligent effort.
Elixhauser resources can be found on the HCUP website. To download the actual comorbidity listing for 2025, click here.
Editor’s note: This Q&A originally appeared in JustCoding. The information was provided by Amy Kratochvil, RHIT, CDIP, CCDS, system director for HIM coding and CDI at UChicago Medicine in Chicago, Illinois, and Tiara Minor, RN, BSN, CCDS, director of CDI at the University of Miami Health System in Miami, Florida, on the August 27, 2025, episode of the ACDIS Podcast.