ICD-10: What about specificity and reimbursement?

March 17th, 2017 / By Clarissa George

In a recent blog, my colleague Jason Mark examined specificity with Atrial Fibrillation (irregular heartbeat) to see if there are noticeable shifts in the specificity of codes being used under ICD-10. He looked at the difference in specificity for Atrial Fibrillation from October 2015 to January 2017. One of the questions raised at the end of Jason’s blog was how unspecified codes might affect reimbursement. Today, I will dig further into this question by examining the average DRG weights in specific vs. unspecific visits with Atrial Fibrillation.

DRG Weights in Specific vs. Unspecific Visits – Atrial Fibrillation

To simplify the discussion, I will use the same January 2017 data that Jason did in his blog. As a reminder, this data is from more than 1,000 3M client facilities. Recall that for Atrial Fibrillation in January 2017 there were: 

  • 160,083 – Total Inpatient visits with one of the four specific atrial fibrillation codes
  • 97,996 – Visits coded with a specified code (I480, I481, I482)
  • 62,087 – Visits coded with the unspecified code of I4891

If the reimbursement rate is higher for visits with specific codes, then the average DRG weight will be higher than those that contain the unspecified code. For Atrial Fibrillation we will compare the 97,996 specific visits to the 62,087 unspecific visits. We would assume visits with more specific codes would have a higher average DRG weight than those that do not, but to double check our assumption let’s look at the following data for January 2017:



Indeed the average DRG weight is higher for visits with a specific code of Atrial Fibrillation than those that have the unspecific code by about 0.03. This shows that reimbursement can be affected by specificity, but it also raises another question: Did the visits with a more specific code just have more complicated reasons for admission that increased this group’s reimbursement? To examine this question, we will filter the data to review visits that only had Atrial Fibrillation as their primary diagnosis or reason for admission. This will help level the comparison as we review visits that are most likely to be similar.

Visits with Atrial Fibrillation as a Primary Diagnosis or Reason for Admit

For visits in January 2017 where Atrial Fibrillation was the primary diagnosis or reason for admission, we see the following numbers:



We can see there are significantly fewer visits where this is the case: 7,977 visits with a specified code and 7,095 visits with an unspecified code – which makes sense since we are trying to look at similar visits. The overall DRG weight is also smaller in terms of total numbers (these visits were less complicated than the entire bucket of visits with Atrial Fibrillation). However, the difference between the two DRG weights is larger. Average DRG weight for visits with a specific Atrial Fibrillation code was 1.25 whereas visits with an unspecific code were 1.14. Thus, the difference is 0.11 or nearly 10 percent which is a much more significant change than looking at all visits that simply contained the code! This means that narrowing the data to look at visits that are more likely to be similar gives a more accurate picture of how specificity is likely impacting reimbursement.