BCG+释放医疗数据的价值迈向更健康、更富裕的英国

Towards

aHealthier,WealthierUK:UnlockingtheValueofHealthcareDataJuly2023BCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data2Who

we

arePage

3Executive

summaryPage

4Chapter01Page

12IntroductionChapter02UsecasesPage

19Page

32Page

51Chapter03ImplementationfactorsChapter04KeyrecommendationsAbout

theauthorsSurveymethodologyReferencesPage

53Page

54Page

55About

the

Centre

for

Growth:BCG|CentreforGrowthBCG’sCentre

forGrowthfocuses

on

acceleratingsustainable

andinclusiveeconomicgrowthintheUKbyworkingwith

businesses,

government,and

widersocietyto

deliver

breakthroughoutcomes.As

partofBCG,

theCentre

forGrowth

bringstogetherideas,

people,

and

actionto

drivetheUK

forward.

Wework

with

ourglobalexpertnetworkto

identifytransformationalopportunities,

connectkeydecision-makers,

andbuildcoalitionsforchange.

We

offer

long-termstrategic

insight,

extensive

cross-sector

expertise,platformsfor

dialogue,

and

biasto

action.About

BCG:Boston

Consulting

Group

partnerswith

leadersinbusiness

andsocietyto

tackletheirmostimportantchallengesand

capture

their

greatestopportunities.

BCG

was

the

pioneerin

businessstrategy

when

itwas

founded

in1963.

Today,wework

closelywith

clientsto

embrace

atransformationalapproachaimedatbenefitingallstakeholders

-empoweringorganisations

togrow,

build

asustainable

competitiveadvantage,and

drivepositive

societal

impact.Our

diverse

globalteamsbringdeepindustryand

functional

expertiseand

arangeofperspectives

thatchallengethe

status

quoandsparkchange.

BCG

deliverssolutions

throughleading-edge

managementconsulting,technologyanddesign,

and

corporate

and

digitalventures.

Wework

ina

uniquely

collaborativemodelacross

the

firm

and

throughout

alllevelsoftheorganisation,

fuelled

by

thegoalofhelpingourclientsthriveandenabling

them

to

make

theworld

a

betterplace.“Collaborationcanachievebreakthroughchange.Opportunitiesfor

disruptioncanenergise

theUKeconomy.

”BCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data4Executive

summaryThe

UK

faces

several

challenges

over

the

comingyears

as

we

exita

period

of

almost

unprecedenteduncertainty.

But

there

are

two

that

stand

out-

thepoor

outlook

for

the

economy

and

the

hugepressure

weighing

on

our

healthcare

system.With

its

vast

amount

of

healthcare

data

andleading

position

in

life

sciences

andartificialintelligence(AI),

the

UK

has

a

unique

opportunityto

unlock

the

value

of

this

resource

and

worktowards

becoming

a

healthier

and

wealthiercountry.

Capturing

the

full

benefits

of

healthcaredata

–

an

opportunity

that

has

been

long

mootedbut

never

grasped

–

can

lead

to

better

patientoutcomes,

more

efficient

healthcare

delivery

andwill

help

drive

R&D,

innovation

and

investmentacross

the

life

sciences

and

tech

industries.

Wherehealthcare

data

has

been

used

in

this

way,

bothregionally

in

the

UK

and

in

other

countries,

therehave

been

significant

benefits

realised.

In

thispaper

we

discuss

the

current

challenges

inThe

country’s

low

productivity,

falling

real

wages,and

lagging

business

investment

are

hitting

theeconomic

growth

outlook

whileinflation

andinterest

rates

arerising

sharply

–

precipitating

acost-of-living

crisis.

At

the

same

time,

both

NHSwaiting

lists

and

the

number

of

people

out

of

theworkforce

due

to

long-term

illness

are

at

recordhighs

of

7.42

million1

and

2.5

million2

respectively.Neither

of

these

challenges

are

insurmountable.But

solving

them

needs

creative

thinking

andurgent

action.utilising

healthcare

data

and

outline

18

keyrecommendations

for

policymakers

to

unlock

thevalue

of

healthcare

data

in

the

UK.

The

fullrecommendation

list

can

be

found

in

Chapter

4.Healthcaredata

can

havemultiple

benefitswhen

usedin

therightwayNearly60%10pp+£200030%reduction

inhospitalisations1improvement

insuicideattemptprevention2saving

on

hospital

admissionfor

a

patient

with

AKI3reduction

inreoperationsafter

complications4•

Sutter

Health

integratedreal-time

patientprogressdataintotheir

clinical•

New

models

combinedelectronic

health

recordsandanswersto•

App

alertsclinicians

topatientsatriskofAcuteKidney

Injury(AKI)•

Datasharingfor

key

value-based

metrics

acrossnetworkdecision-making

processesquestionnaires•

Bringstogether

datafromblood

tests,

medical

historyandclinicaldecision

tools•

Reoperations

due

topostoperative

complicationsafter

lumpectomy

droppedby

27%onaverage•

Delivered

reductions

of

60%in

hospitalisation,

13%

in•

Predicted

suicideriskmoreaccuratelythan

previousmodelsemergency

department

visitsand

70%

in

days

spent

in

ICU1.The

Commonwealth

Fund.Supporting

Patients

Through

Serious

Illness

and

the

End

of

Life:

Sutter

Health’sAIM

Model,

January

2018.

2.Simon

etal.,

2018.

American

Journal

of

Psychiatry.3.UCL.Mobileappspeedsup

review

and

treatment

of

acutekidney

injury,August

2019.

4.BCG.How

DutchHospitals

MakeValue-BasedHealthCare

Work,

2018BCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data5To

understand

publicperceptionsaroundaccessand

useofhealthcare

data,

BCG

conductedarepresentative

surveyofthe

publicinEngland(references

to

the

NHSin

thisreportrefer

toNHSEngland,

butmuch

ofouranalysis

isrelevant

across

allnations

intheUK).

Oursurveyfoundthat,

contraryto

popularbelief,peoplearegenerallyopento

allowingaccesstotheir

healthcare

data.

However,

thepublic’ssupportfordata

sharing

isdependent

ontargetingthemost

impactful

usecases,Recommendation:

Detail

the

outcomesfromspecificusecases

ofmakinghealthcare

datamore

accessible

to

generatepublicsupportandunderstanding.Supportforsharingdata

with

theNHSisveryhigh,

with

90%ofpeoplewillingto

share

datawith

theNHSforanypurpose.

While

supportislowerforotherorganisations,

there

isstill

muchmore

supportthanopposition

–withtheexception

oftechcompanies.

Here,

buildingpublictrustwill

bevital

ifthey

areto

beinvolvedinthisspace.articulatingoutcomes,

and

ensuringthatsecurity

and

privacyconcernsare

addressed.There

is

huge

support

for

sharing

personal

health

data

with

the

NHS

and

moresupport

than

opposition

for

all

other

organisations,

apart

from

tech

companiesDoyousupport

oroppose

sharingyour

personal

healthdata

with

thefollowingforanypurpose?TheNHSPharmaceuticalcompaniesCentralgovernment90%7%

3%41%29%31%1%2%2%29%28%29%30%39%AcademicinstitutionsLifesciences

companiesTechcompanies38%31%33%32%5%13%27%2%58%Source:

BCGHealthcareDataSurvey2023SupportNeither

support

noropposeDon'tknowOpposeBCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data6Our

report

and

survey

demonstrate

that

when

thepotential

benefits

are

clearly

communicated,

andthe

right

processes

are

put

in

place

to

managetrust,

the

public

are

supportive

of

allowing

accessto

their

data.

However,

previous

missteps

meantrust

is

fragile

and

cannot

be

taken

for

granted

orsquandered.

Much

work

is

already

under

way,building

on

the

Goldacre

Review

and

the

NHS’s“Data

Saves

Lives”

strategy.

But

it

is

important

theUK

does

not

miss

the

opportunity

to

progressefforts

ina

way

that

maximises

the

potential

value,both

in

terms

of

patient

outcomes

and

widereconomic

benefits.

We

have

identified

and

testedpublic

support

fora

series

of

actions

that

can

helpachieve

this

dual

value

proposition.theSDEs

includingsocioeconomicanddemographic

data

from

tax

records,

welfareclaimsand

censusrecords,

behaviouralinformationfrom

consumerdata,

andlifestyledata

from

wearablesand

mobilephones.This

will

support

better

identification

of

at

riskgroups

within

the

population,helping

to

preventdisease

before

it

develops

or

worsens.

It

will

alsohelp

to

improve

communication,ensuring

bettertargeting

so

people

are

more

informed

abouttheir

risks

and

healthier

life

choices.II.

Disease

pathwaysThe

move

from

data

sharing,

where

data

istransferred

to

external

parties,

to

data

access,where

data

is

hosted

on

platforms

known

asSecure

Data

Environments

(SDEs)

and

access

iscontrolled,

has

been

under-discussed

with

thepublic.

Our

survey

shows

that

when

people

areengaged

on

this

point,

a

substantial

majority

(86%)said

they

felt

more

comfortable

with

data

accessover

data

sharing.

The

UK

is

therefore

alreadystarting

from

a

stronger

position

than

ever

before.Recommendation:Fully

integrate

the

widestrange

of

healthcare

data

into

SDEs,

includingbiomarkers

and

multimodal

health

data.This

will

help

maximise

understanding

ofdiseases

including

better

mapping

of

howdiseases

spread

and

develop,

and

thebiomarkers

used

to

identify

them.

It

will

alsoallow

for

more

personalised

interventions,as

itincreases

the

knowledge

of

how

different

groupsrespond

to

different

treatments.To

build

on

this

we

believe

it

is

crucial

to

movetowards

targeting

specific

outcome-based

usecases.

These

will

help

build

and

maintain

publicsupport

and,

by

properly

targeting

the

use

casesand

designing

the

SDEs

with

them

in

mind,

thepotential

value

of

data

can

be

maximised.Leveraging

AI

and

machine

learning

is

a

commontheme

whichwill

be

crucial

across

the

piece

ifthese

outcome-based

use

cases

are

to

beachieved.

For

example,

modelling

of

early

AI

R&Dtechnologies

has

already

indicated

a

potentialreduction

in

time

and

cost

of

drug

discovery

by

aminimum

of

25-50%3.III.

Clinical

trialsRecommendation:Improve

the

process

ofsetting

up

and

recruiting

for

clinical

trials

intheUK,

by

developing

an

accessible

‘conciergeservice’

to

quickly

determine

whether

aparticular

trial

is

feasible,as

well

as

tools

toexplore

the

sensitivity

of

inclusion/exclusioncriteria

for

clinical

trial

participants.Along

with

other

steps,

such

as

those

set

out

inthe

recent

Lord

O’Shaughnessy

review,

this

canhelp

restore

the

UK’sposition

as

a

leading

placeto

conduct

clinical

trials.

In

turn,

this

should

helpdrive

investment

and

innovation

into

the

UKacross

related

sectors,

and

ensure

the

UK

is

atthe

forefront

of

healthcare

discovery.Recommendation:

Focus

on

outcome-basedusecases

in

the

followingfour

areas:I.

PreventionRecommendation:

Allow

for

integration

ofawidervariety

ofnon-healthcare

data

intoBCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data7IV.

Clinical

careThis

can

help

improve

diagnosis

in

hospitals,potentially

reducing

waiting

times

andimproving

treatment

by

giving

a

richer

view

ofthe

impact

of

past

treatments

on

differentpatients.Recommendation:Leverage

new

technologiesincluding

machine

learning,generative

AI,

andAI-driven

algorithms

to

optimise

clinical

caredecision-making

and

resource

management

inthe

NHS.We

tested

these

use

cases

with

the

public

inoursurvey

and

found

broad

support

for

all

of

them.This

illustrates

that

when

the

potential

benefitsand

outcomes

of

accessing

personal

health

dataare

properly

explained,people

are

supportive.Thereismajoritysupport

for

data

beingusedin

all

usecasesImagineyourpersonalhealth

data

was

made

accessible

onasecureplatform.

For

eachofthefollowing,would

yousupportoropposeyourdata

beingused?SupportOpposeTohelp

understand

myindividuallikelihood

ofspecific

diseases

orillnesses8%1%77%76%14%16%Enableimprovements

inclinicalcareprocesses

suchasscreening

foranddiagnosing

illnesses6%2%Comparing

any

treatments

I’m

given

with

how

others

respondto

help

researchers

understand

how

to

treat

specific

diseases

better71%19%2%

8%Compilingaregister

ofpotential

organ

orblood

donorsforaccess

by

hospitals64%19%22%2%

15%2%

14%3%

15%Helpidentifyeligibleparticipantsinclinical

trialstospeed

upclinicalresearch62%Helphospital

andmedical

staffrecruitaccording

to

whichservices

havehighest

need58%24%Enabling

the

government

to

understandwhere

tobuildnew

medical

facilities

andhow

best

to

utilise

existing

ones52%27%3%18%Source:

BCGHealthcareDataSurvey2023SupportNeither

supportnor

opposeDon't

knowOpposeBCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data8As

wellastargetingtheseoutcome-basedusecases

there

areseveral

successfactorsthatarecrucial

forrealising

the

full

potential

ofdataandthecreationoftheSDEs:Inthelongerterm,

the

NHSshould

establishpublicdecision

panels,

such

asthepublicparticipationpanelalreadyusedbyGenomicsEngland,

andmore

accessible

data

usageregistersfor

engaging

thepublicindecisionsaroundhow

their

data

willbeaccessed

andused.

Our

surveyshowed42%said

theuseofpublicdecision

panelsmadethem

morecomfortable

with

data

beingcollected

andaccessed,

while

47%were

reassuredbydatausageregisters.

These

steps

are

keyto

ensuringthepublicareempowered

with

therightinformationand

proactivelyinvolved

inthedecision-making

process.Datatransparency

andpublicengagementTrust

and

transparencyareprerequisiteswhen

itcomesto

healthcare

data.

It

isvital

to

proactivelybuildpublictrustand

ensure

transparency

ateverystage

ofdata

access.

This

includesagenuinewillingness

to

understand

andcommunicate

lessons

thathave

beenlearntfrom

past

mistakes.Recommendation:

Put

in

placethe

rightframeworks

and

mechanismsto

deliver

the

leveloftransparency

andinformationneeded,includingacleareffort

to

beopen

aboutwhatlessons

havebeenlearntandhow

processeshavebeen

adapted.

This

willensurethatpublictrustismaintained

over

time.Recommendation:

Use

publicdecision

panelsand

datausageregistersto

engage

the

publicindecisions

aroundhow

their

data

willbeaccessedand

used.

Thiswill

helpensurethey

haveasayindecision-making

processes

and

canreviewand

refresh

theseprocesses

over

time(e.g.assess

what

level

ofengagementisneeded

fromparticipantswithrelevant

characteristics).Intheshortterm,

akeypartof

thiswillbeestablishing

betterpubliccommunicationsaroundhealthcare

datausageand

itspotentialbenefits.

Thisshould

form

partofawiderlong-termpublicengagementstrategy

thatisUseofCOPInoticesDuring

the

pandemic,

ControlofPatientInformation(COPI)noticeswereusedtocoherent

across

NHSdata

projects.

Acommonmisconception

hasbeen

thatindividualsopposeaccessto

their

personal

healthdatabydefault,which

hasledto

ageneralunwillingnesstoengagethepublicon

the

topic.

However,

ourresultsshow

thatnearlythree-quarters

ofpeople(73%)

eitherwantedto

beproactively

toldabouttheuseoftheir

data

(37%)orbeableto

requesttheinformation

(36%)

when

they

wanted.

It

istherefore

importantthatstakeholders

donotshyaway

from

conversations

abouthow,

where,

andwhy

datais

accessed.

Section

3.1details

the

keyareasthiscampaignmustaddressbased

on

oursurveyfindings.expeditethegatheringofandaccess

to

dataacross

thehealthcare

system,

even

ifindividualshad

opted

outofdata

sharing.

COPInotices

wereusedto

supportunderstanding

ofdisease

andwere

criticalto

theUK’srapididentification

anddeliveryoftreatments,

includingvaccines.We

found

there

is

broad

support

(53%)

fordeploying

a

similar

approach

in

the

future.

Thisrises

significantly

if

used

to

address

some

of

themost

acute

challenges

facing

the

NHS.

Nearlythree-quarters

of

respondents

support

the

use

ofnotices

(or

similar)

for

researching

chronic

and/orserious

diseases

(73%)

and

treating

andpreventing

long-term

serious

disease

(72%).

Two-thirds

(65%)

also

supported

the

use

of

theseregulations

to

improve

efficiencies

in

the

NHS

thatwould

reduce

patient

backlog.Recommendation:

Establish

ajoined-uppublicengagementstrategy

thatisconsistentlyadopted

across

allNHSdata

projects,

withaspecificcomms

campaignaroundhealthcaredata

usageandthepotential

benefits.BCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data9Consideration

should

be

given

to

using

thisapproach

for

the

most

difficult

challenges

facingthe

NHS

in

the

future.

However,

it

must

be

done

insucha

way

that

engages

the

public

early,

involvesthem

over

time,

and

clearly

explains

the

benefitsand

end

goal.Recommendation:

Consider

using

COPInoticesmore

frequently

beyondCOVID-19.

Thisincludesutilising

them

forresearchingchronicand/or

seriousdiseases,

treatingand

preventinglong-termseriousdiseases,

and

improvingefficiencies

intheNHSto

reduce

thebacklog,

assupportedbythepublic.Continuingthesame

approach

to

data

access

used

in

COVID-19garneredmajoritysupport

inanumber

of

high

impactareasDoyouthinkitis

appropriateorinappropriatefordata

to

becollected,

usedand

shared

in

asimilarway

to

duringCOVID-19foreachofthefollowingscenarios?Researching

chronic

and/or

seriousdiseases

like

cancer

and

Alzheimer’s73%72%11%

4%

12%12%

4%

11%Treating

and

preventing

long-term

seriousdiseases

e.g.cardiovascular

diseasesImproving

efficiencies

in

theNHStoreducethebacklog65%15%15%5%6%15%15%Responding

toother

futurepublic

healthemergencies64%Understanding

more

aboutmental

healthconditions58%17%7%18%Helpingpharmaceutical

companies

developnew

treatments

for

serious

and/or

long-term

diseases58%56%56%18%6%18%19%19%Researching

and

developing

treatments

for

betterhealth

e.g.

smoking-related

illnesses19%6%Speeding

up

clinicaltrialstohelpidentifyand

launch

new

drugsinthe

UK19%6%Helpingdigital

healthcompanies

developnew

productsbasedon

your

needs33%25%8%34%AppropriateDon't

knowSource:

BCGHealthcareDataSurvey2023Neither

appropriate

nor

inappropriateInappropriateBCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data10Designandoperation

ofSDEs•Bringskillsinto

theNHStoensure

thequalityofdataontheSDEsisofthenecessary

leveland

theworkforceisequippedto

analyse

thedataanduse

theanalyticaltoolsprovided.Aspart

oftheshiftfromdata

sharingtodataaccess,

thegovernment

isbuildingaseriesofSDEsatboth

anational

and

sub-national

level

tobringtogether

data

forresearch.Section3.2includesmoredetail

onourseriesofrecommendationstoensurethey

aresetupinawaythat

maximisespatientandeconomicbenefits.

Thecommonthemeisthat

theSDEsneedtobefullyresourced

overthemedium

andlong-term–apotentiallycostlyexercise.

Itisthereforevitalthat

theirvalueisfullycapturedand

partially

reinvested

tocovertheirrunningcostsanddevelopment

overtime.

Itwillalso

beessential

tohavesufficientsupportfromtheIntegratedCare

Boardsto

ensure

that

theSDEsaresufficientlyfundedand

resourced.••Ensure

sufficientfunding

isputinplacetotarget

outcome-basedusecases.Introducetargetsto

holdIntegratedCareBoards

(ICBs)directlyaccountable

forcreatingresearchopportunitiestoensuresufficientresourcingofSDEs.CapturingvaluefromdataTheNHSmustcaptureand

reinvest

thevaluecreatedfrom

data

access.

Thisisvitalforensuringtheeffectiveness

andlongevity

of

SDEsandrealisingthewide-reachingbenefitsofbetterhealthcaredata

access.Recommendations:Asimplewaytodothiswouldbetochargecertainorganisations

for

access

to

the

SDEs,thoughthismayriskmissingsomeofthevaluecreateddowntheline.

Furthermore,

thecurrentapproachtakenby

theNHSistomakeaccesstothe

SDEsfree.

Ifdataaccessistobefree,it

isvitaltheNHS

usesalternativevalue-sharingmechanismsto•Review

theDataAccessRequestService(DARS)

processonce

theSDEsarefullyupand

running

toensureitisasstreamlinedaspossible,

whilstmaintaining

thevitalsecurityand

ethicalchecksonthoseseeking

toaccessthedata.adequatelycapturethepotentialvalue.

Thismayrequire

aflexible

approachthat

drawsuponarange

ofshort

and

long-termvalue-capturingmechanisms,

depending

onthesituation.

Clearguidance

shouldbeprovidedsoallpartsoftheNHSareconsistently

abletounderstand

thepotentialvalue

indatauseand

negotiate••Ensure

theDARSprocessissufficientlyresourced.Review

and

revise

(whereappropriate)thenecessary

purposeandbenefitsofdataaccesstoalsocapturewiderpotentialbenefitsto

theUK

economyfrom

innovation.appropriateterms

thatdelivermaximum

value.Someofthismustthenbereinvested

back

intolocalNHSservices.•Createaservice

wrapperthatprovidesallNHSSDEs(national

and

sub-national)

with

thesamebasic

governance

andadministrativeprocessessuchasapplicationsforpermissions,

requirementsfor

approval,andmanagement

oftheusersaccessing

thedata.This

final

point

is

crucial.

We

found

that

66%

of

thepublic

do

not

mind

value

or

profits

being

generatedfrom

their

healthcare

data

providing

some

of

thatvalue

is

reinvested

into

the

health

system

and/orthere

are

wider

public

benefits.

When

this

happens,the

level

of

support

for

profit-making

from

healthdata

was

more

than

double

that

of

thoseuncomfortable

with

any

profit-making.

We

believethe

best

way

to

reinvest

into

the

healthcare

systemwould

be

to

createa

central

fund

where

revenuefrom

healthcare

data

is

collected

and

used

toreinvest

in

local

NHS

services,

as

well

as

to

helpresource

the

SDEs

over

time.••MaintainanelementofcompetitionbetweenSDEs–such

asonservicesandanalyticaltools,including

marketplacesfor

them

–tohelpfosterinnovation

and

driveimprovements.IntegratedataacrossthenationalSDEandsub-national

SDEs,aswell

astheFederatedDataPlatformwhichisalso

beingbuilt.BCG|CentreforGrowthTowardsaHealthier,

Wealthier

UK:UnlockingtheValueof

Healthcare

Data11Respondents

were

significantly

more

comfortable

withprofit

beinggenerated,

ifsomeof

thoseprofits

were

reinvestedinthehealth

systemHealthdatacan

beusedto

provide

insightson

drug

developments

andtechnicalinnovations.

Thiscanalso

resultinfuture

profitsfor

thosecompanies,

as

wellaswiderpublicbenefitsthroughimprovedhealthcare

(e.g.

more

effectivetreatmentsfor

disease).

Which

ofthefollowingisclosest

toyour

view?5%6%Comfortable

withhealth

datagenerating

profit

inany

scenario25%Comfortable

withhealth

data

generating29%profit

if

italso

generates

wider

public

benefitsComfortable

withhealth

data

generating

profitif

some

of

the

profit

isreinvested

inthe

health

systemUncomfortable

withany

profitsgenerated

from

health

dataDon’t

know35%Source:

BCGHealthcareDataSurvey2023There

are

fewpoliciesthatcouldaddresspressureontheNHSand

boostoureconomy–makingbetteruseofhealthcare

data

isone.

Furthermore,

itdoes

notneed

majoradditional

investment

orspending.

It

isanopportunitywecannot

afford

to

miss.Recommendations:•Establish

a