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MIT-LCP / mimic-code

MIMIC Code Repository: Code shared by the research community for the MIMIC family of databases
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Question about DRG codes in MIMIC-IV #1561

Open hanyin88 opened 1 year ago

hanyin88 commented 1 year ago

Hello there,

I am hoping to seek some clarification on the DRG Codes available in the latest MIMIC-IV.

In the documentation it was mentioned that: "(DRG) Descriptions have been updated using the latest dictionaries made available from mass.gov and HCUP".

Upon closer look, it appears all HCFA DRG are really MS-DRG. Is this correct?

If so, may I clarify what version of MS-DRG did we use? Of interest, there are about 25 codes not included in MS-DRG v37 and v34 respectively. It seems we have a mixer of older and newer MS-DRG codes.

alistairewj commented 1 year ago

Oh DRGs.. HCFA stands for Health Care Finance Administration, which was renamed the Centers for Medicare and Medicaid Services (CMS) in July, 2001. Medicare was one of the original sources of DRGs which we can call HFCA-DRG. The HCFA-DRGs correspond to the DRGs which were historically used by Medicare’s Inpatient Prospective Payment System. However, the system was changed (before MIMIC-IV) to a new system called Medicare Severity (MS) DRGs. The previous codes and the new codes overlap (!!!). This is one of the reasons why the drgcodes table in MIMIC-III had the full-text of the DRG code with every coded entry and had a drg_type column.

For MIMIC-IV, we don't have this issue at all as the data post-dates the change in coding system. Still it's better to refer to them as MS-DRGs for clarity. I sometimes forget and call them HFCA-DRGs myself though so the docs may have blurred the lines.. lmk if they do anywhere and I can fix.

Strictly speaking each hospitalization has DRG codes using the version available during the year of the hospitalization. We can't release the exact version (that would reveal the year), but you can use anchor_year to upper bound which version they had. Is it very important to know the exact version for your use of the system?

FYI we used the mapping from HCUP to give a description for our DRGs: https://hcup-us.ahrq.gov/db/state/siddbdocumentation.jsp

hanyin88 commented 1 year ago

Oh DRGs.. HCFA stands for Health Care Finance Administration, which was renamed the Centers for Medicare and Medicaid Services (CMS) in July, 2001. Medicare was one of the original sources of DRGs which we can call HFCA-DRG. The HCFA-DRGs correspond to the DRGs which were historically used by Medicare’s Inpatient Prospective Payment System. However, the system was changed (before MIMIC-IV) to a new system called Medicare Severity (MS) DRGs. The previous codes and the new codes overlap (!!!). This is one of the reasons why the drgcodes table in MIMIC-III had the full-text of the DRG code with every coded entry and had a drg_type column.

For MIMIC-IV, we don't have this issue at all as the data post-dates the change in coding system. Still it's better to refer to them as MS-DRGs for clarity. I sometimes forget and call them HFCA-DRGs myself though so the docs may have blurred the lines.. lmk if they do anywhere and I can fix.

Strictly speaking each hospitalization has DRG codes using the version available during the year of the hospitalization. We can't release the exact version (that would reveal the year), but you can use anchor_year to upper bound which version they had. Is it very important to know the exact version for your use of the system?

FYI we used the mapping from HCUP to give a description for our DRGs: https://hcup-us.ahrq.gov/db/state/siddbdocumentation.jsp

Thank you for the super detailed reply and this is tremendously helpful!!! Deeply appreciate the hard work in navigating the complex history.

To answer your question, I am working on a project for DRG prediction, so in the ideal world it would be nice to have a unified version across the database, though I completely realize it would be hard to do. This is not a big deal now I know the historical context, and I could just manually identify those different DRG codes across different years (CMS update the rule yearly).

For the other point you mentioned, currently in MIMIC-iV there are only two groups: HCFA and APR. To your point, it might be a good idea to label HCFA to MS-DRG in future iteration.

One final question if I may, I noticed majority of patients in MIMIC-IV have both HCFA(MS) and APR DRGs assigned, which seems to be unusual as I know in really practice one only need one DRG (based on insurance for the most part) during hospital stay. Is it just how the system works in BIDMC?

Many thanks.

alistairewj commented 1 year ago

OK, possible I left it as HCFA for legacy reasons (tried not to change too much from MIMIC-III). I've forgotten now!

Yeah it's a bit tedious but at least with the full text of the code you can identify the DRG codes which are no longer valid.

One final question if I may, I noticed majority of patients in MIMIC-IV have both HCFA(MS) and APR DRGs assigned, which seems to be unusual as I know in really practice one only need one DRG (based on insurance for the most part) during hospital stay. Is it just how the system works in BIDMC?

Honestly not sure about this one, but codes from both systems exist for every patient, so I suspect some sort of internal mapping table that we don't have insight into.