A recent article in the Daily Mail suggested that the death toll from COVID-19 is 80% higher than currently reported. This was based on a comparison of the 1,649 deaths reported by ONS for March 27th with the figure of 926 deaths reported on that day by the Department of Health and Social Care (DHSC).
Because the number of new deaths reported daily adds to the totals of previous days there is a lag effect. Cumulative totals do not necessarily represent all of the deaths that have occurred up to that date.
The percentage difference was large (80%) at the beginning of the pandemic (late March) but is reducing mainly: because the number of new deaths announced each day is smaller as a proportion to the cumulative total than it was early on.
Here is a worked example based on the recent figures.
The total on the 10th of April is 8,114 with 866 new deaths. Based on how the numbers have been revised over the last four days and assuming the number of new cases stays at 900 for the next week we can estimate what the percentage difference between the figure announced on the 10th April (8,144) is, with what the revised figure will be a week later.
This table explains shows our calculations.
| Date | Assumed number of new cases announced | Number of new cases attributed back to the 10thApril | Revised total for the 10th April | Percentage difference between original and revised number |
| 11th April | 900 | 900 * 0.18 = 162 | 8114 + 162 = 8276 | 8276/8114 = 2% |
| 12th April | 900 | 900 * 0.4 = 360 | 8276 + 360 = 8636 | 8636/8114 = 6.4% |
| 13th April | 900 | 900 * 0.17 =153 | 8636 + 153 = 8789 | 8789/8114 = 8.3% |
| 14th April | 900 | 900 * 0.08 =72 | 8789 + 72 = 8861 | 8861/8114 = 9.2% |
| 15th April | 900 | 900 * 0.05 =45 | 8861 + 45 = 8906 | 8906/8114 = 9.8% |
| 16th April | 900 | 900 * 0.02 =18 | 8906 + 18 = 8924 | 8924/8114 = 10.0% |
| 17th April | 900 | 900 * 0.02 = 18 | 8924 + 18 = 8942 | 8942/8114 = 10.2% |
If the attribution continues as it has done in the past four days, and assuming new cases at or around 900, the total number of deaths is likely to be about 10% higher by the time the numbers are recalculated on the 17th April.
If the average number of new cases over the next week is closer to 1,000 per day then the difference will be higher, at 11.3%. Assuming a worst-case scenario of 1,200 new cases per day, the disparity could be 13.6%. None of these estimations come close to the figures of 70-80%.
Revised NHS figures are close to the ONS figures, and we can assume that when the ONS publish their figures for the 10th April the difference will be much closer than they were on the 27th March.
AUTHORS
Jason Oke is a senior statistician at the Nuffield Department of Primary Care Health Sciences. (Bio here)
Carl Heneghan is Professor of Evidence-Based Medicine, Director of the Centre for Evidence-Based Medicine. (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.
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Source: The Centre for Evidence-Based Medicine
