COVID-19 codelist (icd10)

[qwenww]

Hi, I would like to know when to use three items ["U071", "U072", "U109"] for COVID-19 codelist instead of usual two items ["U071", "U072"]? (U109: Multisystem inflammatory syndrome associated with COVID-19, unspecified), thanks!

[wjchulme]

Reposting a digested answer I wrote in slack a while ago:

Abstract

Since Feb 2021, two more ICD-10 codes for Covid, U099 and U109, have been added on top of the usual U071 and U072. These are used by ONS when reporting Covid-related deaths. See attached image for description, taken from this ONS page. ht @cewalters

To investigate how these ICD-10 codes were being used, we looked at covid-related unplanned hospital admissions and deaths, using different combinations of the codes.

tl;dr -- The new codes appear to never be used for hospital admissions, and only very rarely for death certification. Old studies that didn't include the new codes shouldn't need to be revisited. But it's still worth including them for future studies where relevant.

Methods

We looked at these codes when appearing as primary reason for admission or cause of death, and when appearing as any reason.
We used a simplified version of the comparative booster effectiveness population -- basically, anyone vaccinated with Moderna or Pfizer from late october 2021 to january 2022.

We looked a time to covid-related hospitalisation or death following booster vaccination, broken down by different code combinations, eg U071 only, U072 only, U071;U099, etc

Results

Hospitalisations: No new codes (U099, U109) appeared in coding for hospitalisation. The vast majority were U071-coded events. The rest were U072 or U071;U072.

Deaths: A small number of deaths (<50) included the new code U099, but most of these were accompanied by U071. Very few (<10) covid-related deaths would be missed if U099 was not used to in the identifying codelist. U109 was also used very few times (<10) times, always accompanied by another U071 code.

Notes

Code use may be different in unvaccinated / undervaccinated populations. In particular U109 (multisystem organ failure associated with covid-19) might be more likely to appear, as severe events are more common.

The breakdown of code use considered only the first event containing at least one of the codes after booster vaccination. This means, for example, that a person admitted to hospital with covid under code U071 (confirmed covid), who was later admitted to critical care under code U109 (multisystem organ failure associated with covid-19) will not have been picked up in the summary, because admission to critical care usually means a new hospital spell, and so wouldn't be the first event after vaccination. However, it's possible that the new codes U099, U109 simply aren't available for use when coding hospital events.