Accompanying Conditions of Deaths from COVID-19, March 2020 – February 2022

Methodology for coding of deaths

The figures in this Frontier Series Output are based on deaths that have occurred in Ireland between 01 March 2020 and 28 February 2022, have been registered with the General Register Office (GRO) and subsequently notified to the Central Statistics Office (CSO). These figures are provisional. Final data is published in annual reports.

On receipt of the data, one of the key tasks for the CSO is to assign the Underlying Cause of Death (UCOD). The UCOD refers to the “disease or injury that initiated the train of morbid events leading directly to death” (World Health Organization, 2016, p.31).

The UCOD is classified according to the World Health Organization's International Statistical Classification of Diseases and Related Health Problems 10th Revision (WHO, ICD-10). The hierarchy in which the medical conditions are written on the death certificate impacts on the assignment of the UCOD.

From 01 January 2018, the CSO is using IRIS software to assign the UCOD. IRIS is a European developed automated coding software, endorsed by Eurostat and is maintained by the IRIS institute to include all WHO updates.

Deaths due to COVID-19

The corresponding ICD-10 codes for COVID-19 are

• U07.1 (virus identified) where COVID-19 was confirmed by laboratory testing irrespective of severity of clinical signs or symptoms; and
• U07.2 (virus not identified) where COVID-19 was clinically-epidemiologically diagnosed but laboratory testing is inconclusive or not available (including probable or suspected COVID-19).

A COVID-19 death is defined, for surveillance purposes, as a death resulting from a clinically compatible illness in a probable or confirmed COVID-19 case, unless there is a clear alternative cause of death that cannot be related to COVID-19 disease (e.g. trauma). There should be no period of complete recovery between the illness and death.

It is important to note that there will be a number of deaths where COVID-19 will not be assigned as the UCOD and therefore, the COVID-19 deaths in this analysis will vary from those put into the public domain by the Department of Health.

The coding of causes of deaths in the CSO applies all ICD-10 rules in a consistent manner. The CSO relies on the data provided by medical certifiers who assure the accuracy and completeness of medical conditions on the certificates, including the correct causal sequence which affects the selection of the underlying cause of death.

COVID-19 as a single cause of death

A death certificate can list multiple accompanying medical conditions. The International Form of Medical Certificate of Cause of Death is structured according to specified guidelines (World Health Organization, 1979), attesting a chain of events that resulted in the death.

Where COVID-19 is the single cause of death, no other condition is reported on the medical certificate of cause of death (see Example 1). However, it is possible for a person to have several conditions listed as accompanying medical conditions on the certificate. These may be pre-existing conditions or complications of COVID-19 (see Example 2). In Example 2, COVID-19 is the underlying cause of death as defined by the WHO.

Example 1
1(a)  COVID-19
1(b)  --
2      --

Example 1 is a COVID-19 as a single cause of death. Single cause is where only COVID-19 and no other conditions have been listed on the death certificate.

Example 2
1(a)  Pneumonia
1(b)  COVID-19
2      Diabetes

Example 2 would not be considered a death where COVID-19 was the single cause, as other conditions and complications have been listed with it.

Selection of other conditions recorded in COVID-19 deaths for analysis

The conditions listed in Tables 2 and 3 of this Frontier Series Output were selected as follows:

• For completeness of the data presented, all groupings of diseases are included (highlighted in bold on tables) according to the WHO’s ICD-10 chapters of disease codes.
• More specific diseases and conditions were selected based on the list of medical conditions published by the Health Service Executive (2022) that put people at higher risk from COVID-19. Omitted from tabulation in this release are alpha-1-antitrypsin deficiency and maple-syrup-urine disease because no deaths from COVID-19 occurred with these conditions specified as an accompanying medical condition for the deceased person.
• Some additional diseases are included to provide more context. Breast and prostate cancer are included as the second and third most common malignant neoplasms causing deaths in Ireland. Furthermore, dementia, Alzheimer disease and type 2 diabetes are listed due to the higher risk from COVID-19 in older persons. Finally, pneumonia as the most common respiratory condition mentioned on the death certificates is also added.

References

Health Service Executive (2022) “People at higher risk”, HSE Website. https://www2.hse.ie/conditions/covid19/people-at-higher-risk/.

World Health Organization (1979) Medical Certification of Cause of Death: Instructions for Physicians on Use of International Form of Medical Certificate of Cause of Death (4th edition). Geneva: World Health Organization.

World Health Organization (2016) International Statistical Classification of Diseases and Related Health Problems 10th Revision – Volume 2 Instruction Manual (5th edition). Geneva: World Health Organization.