Methods of collecting biological data:Considerations, challenges and implications

ESRC Research Methods Festival 2012

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Passive smoking

Why collect biological measures?

Prevalence of STDs

Dietary salt levels

Undiagnosed diabetes

Early kidney disease

Vitamin D levels

GeneticsRisk of CVD

Our experience of collecting biological measures

1.

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What have we collected?

Measurements• Height and weight• Waist and hip• Arm circumference• Demi-span• Grip strength• Walking speed• Infant head circ. • Cognitive tests• Balance

Medical measures• Blood pressure• ECG• Lung function• Dental checks•Step tests (fitness)

Samples• Venous blood • Blood spots• Saliva• Urine samples• 24 hour urine• (Tracer water)• Hair

Who should collect what?

2.

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Our traditional approach

Standard interviewer visit + some measures (height and weight)

Nurse follow up visit at participant’s home to collect other measures

Interviewer introduces nurse visit, may make appointment

• NatCen first used nurses in 1994 Health Survey for England

• Requires a special panel of freelance nurses (we have around 150)

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Drawbacks of nurse follow ups: drop out

HSE 2010 (adults)

71% (5,587 visits)

% of interviewed who have nurse

visit

Survey

NDNS Yr 3 74% (698 visits)

ELSA wave 4 86% (8,218 visits)

US (W2Y2 + W3Y1) 65% (4,409 visits)

Nurse HSE sample very

similar to interview:

Slightly fewer smokers and non-

drinkers (esp. men).

Little difference by

Age; sex; BMI; general health;

diet. Slightly more:

Men with high BP

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We have used interviewers to collect…

• Height• Weight• Waist• Saliva sample • Urine samples• Timed walks• Infant length & head

circumference• Grip strength• Cognitive tests

And recently developed protocols to extend interviewer biomarker collection to:

•Blood pressure (Scottish Health Survey)•Dried blood spots (Scottish Health Survey from 2013)

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Drawbacks of nurse follow ups: logistics

Child fasting blood (35%)

• NDNS requires clinics within two hours of each sample point

• Specialist phlebotomists for some visits

Blood to lab within 2 hours for spinning

Nurse visit (74%)

Adult fasting blood (69%)

Child 24 hr urine (74%)

Adult 24 hr urine (80%)

NDNS Interviewe

r visit

Paediatric phlebotomist

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Use of clinics

Diet and Nutrition Survey of Infants and Young Children

• Blood taking from 4 – 18 month olds, immediate spinning of blood

• Feed special tracer water to these infants, specific dose

• Skinfold measuresDecision to use clinic-based follow-up:

• 20 clinics recruited (hospital/private), specific training for staff

• 2 mobile vans with experienced staff (initially for people living far from a clinic)

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Clinic responseSkinfold measure

(99%)

Clinic visit (44%)

Blood (55%)

“Tracer water” taken

(86%)

Interviewer visit

Does it matter who takes the measurements or how they take it?

3.

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…evidence from the Scottish Health Survey

Large scale survey monitoring the health of the Scottish population

Carried out 1995, 1998, 2003 and annually since 2008

Collecting biomeasures using the traditional nurse model since 1995

Switched to using field interviewers in 2012 What impact, if any, will this move have on our

ability to continue to monitor trends in…

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Mean waist measurement, 1995 - 2010

40

50

60

70

80

90

100

110

cm

Men

Women

?

?

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…waist measurements

move to a different (less invasive) protocol

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Blood pressure level, 2008-2010

0

10

20

30

40

50

1998 2003 2008/9 2010 2011

% h

yper

tens

ion

MenWomen

?

?

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…blood pressure

•Protocol unchanged

•Concerns about non-medically trained interviewers collecting it

•Interest in whether “white coat syndrome” extends to nurses

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Validation study objectives were…

1. To establish the degree of correlation between interview and nurse measurements

2. Generate calibration equations that allow for SHeS statistics to be ‘converted’

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How did we do it?

Paired up trained field interviewers and survey nurses (15 pairs)

Pairs visited respondent in own home, taking turns to take BP readings & waist measurements

Purposive sample – oversampled aged 55+300 paired interviews carried out (Mar-May

2012)

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Factors considered

• Order of interviews was randomised

•Carried out consecutively

•Partner not in the home at time of interview

•Same blood pressure machine used

•Participant told whether an interviewer/nurse

•Results from 1st visit not given to participant

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Interview content

Interviewer visit

1. Blood Pressure

2. Waist measurement

Nurse visit

1.Blood pressure

2.Waist measurement (own protocol)

3.Waist measurement (interviewer protocol)

So did it matter who took the

measurements & how?

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Biomarkers – things to considerIt is possible to collect a range of biological measures within a survey based study, but it is important to consider how: Who will collect (interviewer, nurse, clinic, self):

Complexity of measure, protocol, acceptability, analysis requirements, target population

Ethical considerations Training is vital – quality is important! Equipment: ease of use, portability, durability Labs – work with them to agree protocols, check

quality! Data analysis – can be a minefield.

If you want further information or would like to contact us

Lisa Rutherford

Research Director

T. +44 (0)131 221 2555

E. lisa.rutherford@scotcen.org.uk

Visit us online, natcen.ac.uk

Thank you