Death certificate data: COVID-19 as the underlying cause of death

September 16, 2020

Daniel Howdon, Jason Oke, Carl Heneghan

Overall about one in thirteen deaths with COVID-19 on the death certificate did not have the disease as the underlying cause of death; however, this proportion has risen substantially to nearly a third over the last eight weeks.

World Health Organisation guidelines state that “COVID-19 should be recorded on the medical certificate of cause of death for ALL decedents where the disease, or is assumed to have caused, or contributed to death, i.e. COVID-19 is the underlying cause of death”. Such an example would be someone who has developed pneumonia as a result of COVID-19, dies from acute respiratory distress. Alternatively, COVID-19 may be present on the death certificate as a significant condition contributing to death but not the underlying cause. These guidelines are clear that in such cases these deaths “are not deaths due to COVID-19 and should not be certified as such”:

We set out to determine how many COVID-19 deaths where COVID-19 is the underlying cause and when  COVID-19 is not considered as the underlying cause using Public Health England (PHE) weekly reports on excess mortality (published since the week ending 3 July 2020). 

This allowed us to address the question of whether COVID-19 is the underlying cause of death when it appears on the death certificate.

What did we find

While we found that roughly one in thirteen (7.8%) deaths with COVID-19 on the death certificate did not have the disease as the underlying cause of death, this proportion has risen substantially to 29% (nearly a third) for the last eight weeks of reporting.

What we did

Deaths are classified by the underlying cause of death (“the disease or injury which initiated the train of morbid events leading directly to death”) according to major groupings such as ischaemic heart disease and cancer, and a final catch-all “All Other Causes (Excl. COVID-19)”. We use this information to infer information about deaths where COVID-19 is certified as the underlying cause of death.

First, we use information from the most recent at the time of writing excess mortality report, based on deaths until 28 August to infer the total number of deaths where COVID-19 was stated as the underlying cause of death:

• The sum of the total deaths in Table 7 of the report shows 218,143  deaths without COVID-19 certified as the underlying cause of death. 
• Figure 2 of the report shows 263,826 registered deaths in this period.

The difference between these two numbers gives the total number of deaths where COVID-19 is certified as the underlying cause: 45,683.

• Figure 2 reports 49,560 deaths where COVID-19 is mentioned on the death certificate. 

This implies that there were 3,877 (7.8%) death certificates, where COVID-19 was not the underlying cause of death (49560-45683).

Second, we use similar calculations for every mortality report published to date to obtain the total number and proportion of death certificates that featured COVID-19, not as the underlying cause of death. These numbers are tabulated by week below:

While the total proportion of COVID-19 death certificates not featuring COVID-19 as the underlying cause of death is only 7.8%, this figure has stood at almost 30% (465 of 1,617 deaths in total) over the time period that PHE have published the weekly mortality report. 

This is broadly in line with figures published by the National Records of Scotland indicating that COVID-19 was the underlying cause in 94.6% of death certificates with any such mention until week 21, but only 76.3% from week 22 to week 32.

While death certification is rightly regarded as a gold standard for the ascertainment of cause of death, it is important to be able to distinguish between deaths where COVID-19 was a contributory cause from those where COVID-19 was the underlying cause of death. It appears that, over the course of the epidemic, a change to the respective composition of deaths in this regard has taken place.

The distinction between the underlying cause of death and any other mention on the death certificate will be increasingly important as we enter the autumn and winter months, where increases in respiratory illness are observed annually. This is particularly so since the ONS’s weekly release of data includes a breakdown of deaths featuring COVID-19 according to whether it appeared in any mention on the death certificate, and of a broad classification of ICD-10 codes only according to whether any featured as the underlying cause of death.

Daniel Howdon is a Senior Research Fellow in Health Economics, Leeds Institute of Health Sciences. Bio here 

Jason Oke is a Senior Statistician at the Nuffield Department of Primary Care Health Sciences and Module Coordinator for Statistical Computing with R and Stata (EBHC Med Stats), and Introduction to Statistics for Health Care Research (EBHC), as part of the Evidence-Based Health Care Programme.

Carl Heneghan is Professor of Evidence-Based Medicine, Director of the Centre for Evidence-Based Medicine and Director of Studies for the Evidence-Based Health Care Programme. (Full bio and disclosure statement here)

Disclaimer: the article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the authors and not necessarily those of the host institution, the NHS, the NIHR, or the Department of Health and Social Care. The views are not a substitute for professional medical advice.