Calculating and comparing COVID-19 death rates is not a simple matter. Linda Hantrais (LSE) and Susanne MacGregor (LSHTM) explain why, and how these complex processes enabled public figures, journalists and social media users to spread misleading information

Hantrais, Linda

MacGregor, Susanne

English

LSE Research Online

Containing	COVID,	part	2	|	The	problem	of	unreliableand	incompatible	evidenceCalculating	and	comparing	COVID-19	death	rates	is	not	a	simple	matter.	Linda	Hantrais	(LSE)	and	SusanneMacGregor	(LSHTM)	explain	why,	and	how	these	complex	processes	enabled	public	figures,	journalists	and	socialmedia	users	to	spread	misleading	information.Read	the	first	post	in	the	seriesStatisticians	became	aware	early	in	the	pandemic	that	issues	with	data	collection	and	reporting	methods	wouldmake	trends	in	published	rates	of	infections	and	deaths	difficult	to	interpret,	compare	and	explain.	They	were	quickto	point	out	that	raw	numbers	are	not	reliable	indicators	for	comparing	even	absolute	levels	of	infections	and	deathsacross	countries.	Their	warnings	went	largely	unheeded,	as	the	media	and	political	opponents	continued	to	useheadline	figures	to	contrast	performances	across	countries,	and	to	blame	government	leaders	for	their	relativefailures	to	contain	the	spread	of	the	virus.According	to	the	World	Health	Organisation’s	definition,	issued	on	16	April	2020,	a	COVID-19	death	results	‘from	aclinically	compatible	illness,	in	a	probable	or	confirmed	COVID	case,	unless	there	is	a	clear	alternative	cause	ofdeath	that	cannot	be	related	to	COVID	disease’.	In	the	same	document,	WHO	advised	that,	on	medical	certificates,cause	of	death	should	be	notified	as	COVID	‘for	ALL	decedents	where	the	disease	caused,	or	is	assumed	to	havecaused,	or	contributed	to	death’,	implying	in	the	last	case	that	the	disease	may	have	accelerated	death	from	othercauses.Despite	WHO	recommendations,	national	datasets	used	to	track	the	spread	of	the	virus	and	its	lethality	remainedinconsistent	between	countries.	National	registrations	of	COVID	deaths	also	varied	over	time	within	countriesaccording	to	whether	WHO	definitions	were	applied	and	how	they	were	adapted	in	different	settings	−	hospitals,care	homes	or	the	community	−	and	for	national	or	local	monitoring	purposes.	The	most	accurate	records	wereconsidered	to	be	those	based	on	a	clinical	judgement	in	a	hospital	setting	confirmed	by	a	positive	test	as	theunderlying	or	probable	cause	of	death,	and	collated	at	regional	or	national	level.	In	the	absence	of	a	reliablepositive	test	and	other	known	underlying	conditions,	certification	referred	to	an	expanding	list	of	recognisedsymptoms.Miscounting	could	be	attributed	to	missing	data,	incompatibility	of	data	from	different	sources	as	well	as	collatingand	processing	delays	when	laboratory	test	confirmation	was	awaited.	Under-reporting	arose,	particularly	in	theearly	stages	of	the	pandemic,	if	official	data	included	only	deaths	in	hospitals	confirmed	by	laboratory	tests.	Whendeaths	in	care	homes	and	the	community	were	added,	as	in	France	on	4	April	2020,	spikes	were	recorded	in	thecumulative	statistics.	Fluctuations	in	daily	rates	could	also	be	attributed	to	delays	in	reporting	deaths	occurring	atweekends	until	the	following	week.National	datasets	used	to	track	the	spread	of	the	virus	and	its	lethality	remained	inconsistent	betweencountriesConversely,	one	of	the	reasons	evoked	to	explain	the	persistently	high	death	rate	in	Belgium	was	that	their	statisticsincluded	all	deaths	where	COVID	was	the	‘probable’	cause.	Over-counting	could	also	result	from	revisions	todefinitions.	In	August	2020,	Public	Health	England	controversially	changed	its	definition	of	deaths	to	bring	it	into	linewith	practices	in	other	regions	in	the	UK	and	elsewhere.	Application	of	the	new	definition	was	calculated	to	havereduced	the	total	count	by	over	5,000	deaths.	But,	as	noted	by	Worldometer,	no	downward	adjustment	could	bemade	retrospectively	to	the	‘cumulative	count’	in	international	tables.LSE Covid 19 Blog: Containing COVID, part 2 | The problem of unreliable and incompatible evidence Page 1 of 2		Date originally posted: 2021-04-29Permalink: https://blogs.lse.ac.uk/covid19/2021/04/29/containing-covid-part-2-the-problem-of-unreliable-and-incompatible-evidence/Blog homepage: https://blogs.lse.ac.uk/covid19/In	addition,	testing	was	far	from	being	routine	worldwide	and	was	known	to	return	false	negatives	and	positives,which	explained	why	the	virus	could	be	variously	mentioned	on	a	death	certificate	as	the	probable,	presumptive,suspected	or	confirmed	cause	of	death.	Some	countries	were	testing	only	symptomatic	individuals,	whereas	otherstested	asymptomatic	cases	believed	to	be	at	high	risk	of	being	infected	and	infectious.	Statistics	for	the	number	ofmild	cases	in	the	community	were	most	prone	to	under-counting.	In	countries	with	a	high	positive	rate	of	infections,the	number	of	confirmed	cases	was,	therefore,	likely	to	represent	only	a	small	fraction	of	the	real	number.Discrepancies	in	reporting	practices	made	comparisons	unreliable,	not	only	between	countries	and	regions	withinthem,	but	also	over	time	as	testing	became	more	widely	available.	A	relatively	high	incidence	of	cases	and	deathsper	million	inhabitants	might	reflect	the	efficacy	of	a	testing	strategy	rather	than	the	true	incidence	of	the	diseaseand	its	lethality.	Observations	such	as	these	undermined	the	value	of	comparing	case	fatality	rates	(the	proportionof	COVID	deaths,	compared	to	the	total	number	of	cases	diagnosed).To	overcome	the	seemingly	intractable	problems	of	accurately	monitoring	death	rates,	public	health	expertsadvocated	the	calculation	of	all-cause,	age-adjusted	excess	mortality	directly	or	indirectly	attributable	to	the	virus.Where	available,	early	evidence,	by	June	2020,	indicated	close	to	a	two-fold	increase	in	excess	mortality	in	thecountries	worst	affected	by	the	pandemic.	Over	a	longer	period,	rates	tended	to	level	off,	although	other	collateraldamage	was	reported	due	to	delays	in	treatment	of	otherwise	preventable	or	curable	diseases.	Estimates	of	theimpact	on	the	quality	of	life	demonstrate	that	significant	numbers	of	years	of	life	were	being	lost	among	people	whodid	not	die	from	the	disease.In	addition	to	the	lessons	that	can	be	drawn	about	the	caution	needed	in	understanding,	interpreting	and	usingdifferent	data	sources	to	produce	reliable	evidence	with	which	to	inform	policy,	governments	had	to	consider	howbest	to	prevent,	contain	and	counter	the	spread	of	false	or	misleading	information.	Misinformation	came	not	onlyfrom	viral	posts	on	social	media,	but	also	from	comments	made	by	public	figures,	and	statements	printed	orbroadcast	by	journalists.This	post	represents	the	views	of	the	authors	and	not	those	of	the	COVID-19	blog,	nor	LSE.LSE Covid 19 Blog: Containing COVID, part 2 | The problem of unreliable and incompatible evidence Page 2 of 2		Date originally posted: 2021-04-29Permalink: https://blogs.lse.ac.uk/covid19/2021/04/29/containing-covid-part-2-the-problem-of-unreliable-and-incompatible-evidence/Blog homepage: https://blogs.lse.ac.uk/covid19/

Containing COVID, part 2. The problem of unreliable and incompatible evidence

http://eprints.lse.ac.uk/110578/1/covid19_2021_04_29_containing_covid_part_2_the_problem_of_unreliable.pdf

Containing COVID, part 2. The problem of unreliable and incompatible evidence

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