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Nigel Unwin a Departments of Medicine and Epidemiology
and Public Health, University of Newcastle, Medical School, Newcastle
NE2 4HH, b Department of Public Health
Medicine, County Durham Health Authority, Durham DH1 5XZ, c Department of Clinical
Biochemistry and Metabolic Medicine, University of Newcastle, Newcastle
upon Tyne NE2 4HH, d Department of Physiology, University of Sunderland, Sunderland
SR1 3SD
Correspondence to: Dr Unwin n.c.unwin{at}ncl.ac.uk
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Abstract |
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Objective: To compare the implications of four widely
used cholesterol screening and treatment guidelines by applying them to
a population in the United Kingdom.
Design: Guidelines were applied to population based
data from a cross sectional study of cardiovascular disease and risk
factors.
Setting: Newcastle upon Tyne, United Kingdom.
Subjects: General population sample (predominantly of
European origin) of 322 men and 319 women aged 25-64 years.
Main outcome measures: Proportions recommended for
screening and treatment.
Methods: Criteria from the British Hyperlipidaemia
Association, the British Drugs and Therapeutics Bulletin
(which used the Sheffield table), the European Atherosclerosis Society, and the American national cholesterol education programme were applied
to the population.
Results: Proportions recommended for treatment varied
appreciably. Based on the British Drugs and Therapeutics
Bulletin guidelines, treatment was recommended for 5.3% (95%
confidence interval 2.9% to 7.7%) of men and 3.3% (1.5% to 5.3%)
of women, while equivalent respective values were 4.6 (2.3 to 6.9) and
2.8 (1.0 to 4.6) for the British Hyperlipidaemia Association, 23% (18.4% to 27.6%) and 10.6% (7.3% to 14.0%) for the European
Atherosclerosis Society, and 37.2% (31.9% to 42.5%) and 22.2%
(17.6% to 26.8%) for the national cholesterol education programme.
Only the British Hyperlipidaemia Association and Drugs and
Therapeutics Bulletin guidelines recommend selective screening.
Applying British Hyperlipidaemia Association guidelines, from 7.1%
(4.3% to 9.9%) of men in level one to 56.7% (51.3% to 62.1%) of
men in level three, and from 4.4% (2.1% to 6.7%) of women in level
one to 54.4% (48.9% to 59.9%) of women in level three would have
been recommended for cholesterol screening. Had the Drugs and
Therapeutics Bulletin guidelines been applied, 22.2% (16.5%
to 27.9%) of men and 12.2% (8.6% to 15.8%) of women would have been
screened.
Conclusions: Without evidence based
guidelines, there are problems of variation. A consistent approach
needs to be developed and agreed across the United Kingdom.
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Key messages
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Introduction |
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Considerable attention has been focused recently on
promoting evidence based practice and the potential of guidelines to
inform and support appropriate care and changes in clinical
behaviour.1-3 Guidelines have been drawn up on the
prevention of coronary heart disease
in particular, on the screening
and management of patients with lipid disorders. Guidance on the use of
statins, based on the Sheffield table,4 was recently
circulated to all doctors in the United Kingdom.5 There
are important differences in the recommendations of the major
guidelines, however, yet neither these differences nor the implications
for clinical practice have been studied.
We have applied data from a population based survey to the different
guidelines for a population aged 25-64 years.6 We aimed to
describe the potential implications of differences in commonly
available and widely promoted guidelines produced by the British
Hyperlipidaemia Association,7 the British Drugs and
Therapeutics Bulletin,8 the European
Atherosclerosis Society,9 and the American national
cholesterol education program.10
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Methods |
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Recruitment and data collection
The data used in this paper are from the Newcastle heart
project
a population based study of coronary heart disease, diabetes,
and associated risk factors in the general (predominantly of European
origin), Chinese, and South Asian populations of Newcastle upon
Tyne.6 We have used data from the general population for this paper. This was a population based sample from the patient register of the Newcastle Family Health Services Authority, the list of
all individuals in Newcastle registered with a general practitioner. We
took an age and sex stratified random sample of those aged 25 to 64 years after removing any Chinese sounding names (less than 0.5% of the
sample).11
Lipid analyses
Subjects were recruited to the study between April 1993 and
November 1994. After overnight fasting, subjects' height and weight
were measured, their body mass index (kg/m2) was computed,
and a fasting blood sample was taken. Until May 1994 the lipid analyses
were performed on a Cobas Bio centrifugal analyser (Roche Products Ltd,
Welwyn Garden City) and after this date a DAX analyser was used (Bayer
plc, Basingstoke). Throughout the study period, the laboratory
participated in an external quality assurance scheme. This showed no
changes in bias (inaccuracy) for cholesterol or high density
lipoprotein cholesterol. However, the data for triglycerides confirmed
that the DAX data showed a positive bias relative to the Cobas Bio data
and therefore results obtained with the DAX were adjusted as previously
described.12 The low density lipoprotein cholesterol
concentration was calculated using the Friedewald
formula.7
Cardiovascular data
Subjects had two blood pressure measurements. These were
made by trained observers using a standard mercury sphygmomanometer
with an alternate size cuff.13 A 12 lead electrocardiogram was recorded with the subjects at rest. The findings were coded according to the Minnesota manual by two independent observers; a third
observer was used where the two disagreed.14 Each subject completed a questionnaire, which included items on diabetes,
hypertension, coronary heart disease, and stroke (all diagnosed by a
doctor); smoking status; causes of death in any parents or siblings who had died; and the World Health Organisation questionnaire on
intermittent claudication.15 For women, the questionnaire
also inquired about age at the time of the menopause, and any factors
affecting its onset. Local ethical committee approval was received for
the study and all subjects gave informed consent before participating.
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Applying the guidelines
Space does not permit a detailed description of the
guidelines. Here, we have focused on the people for whom the guidelines
recommend intensive treatment in the form of rigorous dietary
intervention underpinned by professional dietetic advice, with or
without drug treatment. Table 1 summarises how we applied each of the
guidelines to the data. The European Atherosclerosis Society and
national cholesterol education program guidelines specify two
target levels for active intervention: one for drug treatment (if a
trial of dietary intervention fails) and the other for intensive
dietary intervention only. Table 2 gives the definitions of the
different conditions and risk factors we used in applying the
guidelines to the study population.
Data analysis
Data were analysed using SPSS software. Results are
presented for 20 year age groups and for all ages (25-64 years) for men
and women separately. The results for all ages were age adjusted to the
1991 England and Wales male and female populations respectively.
Confidence intervals were calculated using Confidence Interval Analysis
software (BMJ Publishing, London).
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Results |
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Altogether 322 men and 319 women aged 25-64 were screened, giving a response rate of 67%. Most subjects were European; 10 men and four women had South Asian sounding names.11 Table 3 shows the percentages of men and women with the risk factors and conditions used in the analyses. The age adjusted total cholesterol concentrations were mean (SD) 5.6 (1.1) mmol/l in men and 5.4 (1.2) in women; the mean high density lipoprotein cholesterol concentrations were 1.3 (0.4) mmol/l and 1.6 (0.4) respectively; and the mean low density lipoprotein cholesterol concentrations were 3.4 (1.1) mmol/l and 3.2 (1.0) respectively.
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Table 4 shows the proportions of men and women who would be screened for cholesterol concentration if the guidelines of the British Hyperlipidaemia Association and the Drugs and Therapeutics Bulletin were followed. The proportions vary widely from 4.4% in women of all ages on the first level of the British Hyperlipidaemia Association guidelines to over 50% for both men and women on the third level.
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Table 5 shows the percentages of men and women recommended for treatment according to the different guidelines. In both men and women, the highest percentages recommended for treatment are associated with the national cholesterol education program guidelines. Here 37% of men and 22% of women met the criteria for active intervention, approximately evenly divided between those who would be recommended for intensive dietary treatment only and those who would be recommended for drug treatment if dietary measures failed to achieve target levels. The British Hyperlipidaemia Association guidelines produced the lowest percentages recommended for treatment (initially intensive dietary measures with drug treatment if target levels were not reached). These were 4.6% of men and 2.8% of women. Although the percentages recommended for treatment by the British Hyperlipidaemia Association and Drugs and Therapeutics Bulletin were similar, the individuals who would have been treated often differed (see figure). Only 2.2% of the population were recommended for active intervention by both guidelines; an additional 2.1% were recommended by the Drugs and Therapeutics Bulletin guidelines only and 1.5% by the British Hyperlipidaemia Association only.
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The figures for the British Hyperlipidaemia Association guidelines in
table 5 apply to the whole population
that is, irrespective of whether
the individuals met the criteria for screening by these guidelines. The
figures are lower if they are based only on those individuals who meet
both the screening and treatment criteria. Thus, the percentage of men
and women who met level one screening criteria and treatment criteria
were 2.7% and 1.4% respectively, while proportions for level two were
3.0% and 1.4% and those for level three were 3.7% and 2.4%. For the
men and women together, the sensitivity (those defined as needing
treatment who would be screened divided by all those needing treatment)
for screening level three was 83.3%, and the specificity (those
defined as not needing treatment who would not be screened, divided by
all those not needing treatment) was 45.5%. The criteria for screening
and treatment for the Drugs and Therapeutics Bulletin
are such that all those who meet the criteria for treatment also meet
the criteria for screening, giving, by default, a sensitivity of 100%.
The specificity was 86.6% for men and women together.
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Discussion |
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Strengths and weakness
This paper aimed to describe the differing implications of
commonly available and widely promoted British (British Hyperlipidaemia
Association, Drugs and Therapeutics Bulletin), European
(European Atherosclerosis Society), and American (national cholesterol
education program) guidelines for the management of hyperlipidaemia. To apply the guidelines to our data we needed to
make several assumptions, sometimes because of the vagueness of the
guidelines and sometimes because of the limitations of our data. These
included, for example, basing "a strong family history of premature
coronary disease" on reported death from coronary heart disease in a
first degree relative, as we did not have data on non-fatal events in
relatives.
160/95 mm Hg or taking
antihypertensive treatment) in men are similar to those for England as
a whole in 1993/94.17 The prevalence of hypertension in
women in our sample is around half that found in the health survey.
However, the data we used here are broad and have enabled us to apply
most criteria from the different guidelines. Thus, although we cannot claim that our results reflect accurately the proportion of the population who require treatment in a clinical context, we are confident that they do reflect reasonably the relative differences between the guidelines for screening and treatment, and this was the
primary purpose of this study.
Implications of the findings
There were wide differences between the implications of
some of the guidelines. The highest proportions of men (37%) and women
(22%) came within the treatment category where the national cholesterol education program guidelines were applied. The proportions of men and women recommended for treatment by the guidelines of the
British Hyperlipidaemia Association and Drugs and
Therapeutics Bulletin were similar
men 4.6% compared with
5.3% and women 2.8% compared with 3.3% respectively. However, the
individuals who would have been treated differed (figure).Thus, it is
not simply that some guidelines suggest more aggressive intervention
but also that they advise treatment for different subgroups. It is also
clear that even the most liberal screening criteria recommended by the
British Hyperlipidaemia Association (level three in table 1) would not
identify all patients recommended for treatment by those guidelines.
guidelines of
the British Hyperlipidaemia Association, European Atherosclerosis Society, and criteria based on the Sheffield table were used, and, most
recently, guidance has been issued from the Standing Medical Advisory
Committee based on the Sheffield table.5 The implication
is that there are considerable inconsistencies in the management of
hyperlipidaemia within the United Kingdom. It has been previously
observed that locally produced guidelines for the use of anticoagulants
in atrial fibrillation and widely used hypertension guidelines also
differ greatly in their implications for numbers
treated.
20 21
Clear guidance needed
The need for consistent clear guidance on screening for and
management of hyperlipidaemia is ever more pressing as evidence of the
effectiveness of newer but expensive agents, the statins,
accumulates.22-24 Unfortunately, recent guidance issued to all doctors in the United Kingdom5 falls short of what
is required
it considers only drug management, fails to present the evidence, and ignores issues of cost effectiveness.25 It
adds to the confusing array of guidelines illustrated in this paper rather than helping to identify and resolve the reasons for differences between them.
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Acknowledgments |
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Professors George Alberti and Raj Bhopal, Dr Martin White, Bill Watson, and Jane Harland were all part of the team who designed and managed the data collection for the Newcastle Heart Project. Dr Peter Stephenson, Sisters Margaret Miller, Catherine Turner and Mavis Brown, and nurse Amanda McEwan helped with data collection, assisted at times by Dr Dalip Singh. We thank N Keen for ECG coding and Martin White, Julie Yallop, and Jane Harland for commenting on a draft of this paper.
Funding: Newcastle and North Tyneside Health Authority, Barclay Trust, and British Diabetic Association.
Conflict of interest: None.
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References |
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(Accepted 6 July 1998)
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