methods of collecting biological data:
DESCRIPTION
ESRC Research Methods Festival 2012. Methods of collecting biological data:. Considerations, challenges and implications. Passive smoking. Dietary salt levels. Vitamin D levels. Risk of CVD. Prevalence of STDs. Undiagnosed diabetes. Early kidney disease. Genetics. - PowerPoint PPT PresentationTRANSCRIPT
Methods of collecting biological data:Considerations, challenges and implications
ESRC Research Methods Festival 2012
2
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.
4
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.
6
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)
7
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
10
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)
11
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.
13
…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
?
?
15
…waist measurements
move to a different (less invasive) protocol
16
Blood pressure level, 2008-2010
0
10
20
30
40
50
1998 2003 2008/9 2010 2011
% h
yper
tens
ion
MenWomen
?
?
17
…blood pressure
•Protocol unchanged
•Concerns about non-medically trained interviewers collecting it
•Interest in whether “white coat syndrome” extends to nurses
18
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
Visit us online, natcen.ac.uk
Thank you