About primary cause of admissions for Elixhauser comorbidity compuation

Prerequisites

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Description

Hi!
My questions is regarding the computation of comorbidities using the queries in:

• https://github.com/MIT-LCP/mimic-code/blob/main/mimic-iii/concepts/comorbidity/elixhauser_ahrq_v37_no_drg.sql
• https://github.com/MIT-LCP/mimic-code/blob/main/mimic-iii/concepts/comorbidity/elixhauser_ahrq_v37.sql

1. Both queries use seq_num = 1. Which is not the standard way of computing comorbidities, these should actually be excluded. Why is this the case in these scripts? It is confusing when you first see the code. Plus it is hard to see the difference between both scripts as they are both no_drg right? (by considering seq_num=1)

2. Only https://github.com/MIT-LCP/mimic-code/blob/main/mimic-iii/concepts/comorbidity/elixhauser_ahrq_v37_no_drg.sql mentions this at the beginning of the script:

-- This code uses the latest version of Elixhauser provided by AHRQ
-- However, it does not filter based on diagnosis related groups (DRGs)
-- As such, "comorbidities" identified are more likely to be associated with the primary reason for their hospital stay

-- The code:
-- removes "primary" ICD9_CODE (seq_num != 1)
-- uses AHRQ published rules to define comorbidities

Does this later bit means that ny replacing the current "seq_num = 1 " by "seq_num != 1" the comorbidities will be computed with drg filter?

Thank you!

Compare mimic-iii/concepts/comorbidity/elixhauser_ahrq_v37_no_drg.sql with mimic-iii/concepts/comorbidity/elixhauser_ahrq_v37.sql, starting with their diagnosis filters and comments. Check the referenced AHRQ rules and MIMIC-III diagnosis fields; done means the distinction between the queries and the seq_num behavior is clearly documented.