Strategies for reducing coronary heart disease and desirable limits for blood lipid concentrations: guidelines of the British Hyperlipidaemia Association

Approaches to the management of hypercholesterolaemia

Patients with hypercholesterolaemia need to be carefully evaluated for underlying secondary or genetic causes. All such subjects require dietary advice. Those with total cholesterol levels persistently in excess of 6.5 mmol/l despite diet, and in the presence of multiple cardiac risk factors may need drug therapy. Drug therapy is likely to be life-long and the potential benefits need to be carefully assessed against the long-term safety of the agents employed.

Laboratory facilities for investigating lipid disorders in the United Kingdom: results of the British Hyperlipidaemia Association survey

AIMS

To determine the availability of facilities for the investigation of hyperlipidaemia in the United Kingdom.

METHODS

A questionnaire was sent to all health districts in the United Kingdom.

RESULTS

The response rate was 81%. All laboratories used enzymatic techniques to measure serum triglyceride and cholesterol concentrations, although there were differences in standardisation procedures. Reference ranges for serum lipids were quoted by 58% of laboratories while 50% quoted "desirable limits". Almost half specified that fasting blood samples were required. High density lipoprotein cholesterol concentrations were estimated by 75% and apolipoproteins AI and B by 14% of laboratories; there were differences in specimen type and considerable diversity in procedures used for measurement.

CONCLUSIONS

Many laboratories were unaware of current recommendations for screening for hypercholesterolaemia in the community. The present survey indicated an urgent need for the introduction of better reference methods, standardisation, and quality assurance procedures before apolipoproteins become a routine part of coronary heart disease risk assessment.

Importance of Routine Measurement of HDL with Total Cholesterol in Diabetic Patients

The prevalence of hypercholesterolaemia and the frequency of a reduced HDL-cholesterol (at different cholesterol concentrations) were evaluated in a group of 400 diabetic patients attending a single diabetic clinic. Despite regularly supervised diabetes, including dietary advice, over one quarter of the patients had a serum total cholesterol concentration > 6.5 mmol/1, while over a quarter of the non-insulin treated and one eighth of the insulin treated diabetic subjects had an HDL-cholesterol <0.9 mmol/1, with a greater prevalence in the males compared with the females. More than 60% of all the diabetic patients who had a reduced HDL-cholesterol <0.9 mmol/1 also had a total cholesterol concentration <6.5 mmol/1. When the total/HDL-cholesterol ratio was calculated more non-insulin treated subjects had a value >4.5 as compared with insulin treated diabetic patients.

When comparisons were made between an age matched group of diabetic patients ( n=185) and a group of non-diabetic subjects attending for a health screen ( n=155), the frequencies of serum cholesterol concentrations greater than 5.2, 6.5, and 7.8 mmol/1 were similar for both groups. Significantly greater numbers of diabetic patients had a reduced HDL-cholesterol <0.9 mmol/1 (at any level of serum cholesterol) and a total/HDL cholesterol ratio >4.5.

This study has shown that the measurement of serum total cholesterol concentration alone will not characterize many subjects who are at risk of macrovascular complications due to a reduced HDL-cholesterol. As serum cholesterol and HDL-cholesterol can both be measured in the non-fasting state, routine measurement of HDL-cholesterol together with total cholesterol should be undertaken in all diabetic subjects and in other patient groups at high risk of cardiovascular disease.

Mismatch of coronary risk and treatment intensity under the National Cholesterol Education Program guidelines

OBJECTIVE

To assess the match between multifactorial risk of coronary heart disease (CHD) and treatment intensity under the National Cholesterol Education Program (NCEP) guidelines for primary prevention of CHD.

METHODS

The multiple logistic regression equation from the Framingham Study was used to derive predicted risks for development of CHD over eight years of follow-up for different age-gender groupings, with serum total cholesterol (TC) values chosen in light of the NCEP cutoff points for both TC and low-density-lipoprotein cholesterol levels. Additional risk factors--hypertension, glucose intolerance, and smoking--were considered in combination for each of these values.

RESULTS

Controlling for the effects of age and gender, there is little difference in the ranges of absolute CHD risks for persons who would receive interventions of differing intensities (i.e., general dietary advice, dietary treatment, or drug therapy). Those who are candidates for drug treatment because of serum lipids alone are often at low levels of risk for the development of CHD when compared with those of the same age with lower TC values who have other risk factors. Discrepancies in CHD risk are wider still when age is also allowed to vary. Furthermore, in every age grouping, women with high TC levels (e.g., 6.9 mmol/L) and two other risk factors are eligible for drug treatment but have a CHD risk that is no higher, and often much lower, than that of males with one other risk factor and TC levels of 4.8 mmol/L or 5.7 mmol/L who are candidates for dietary advice or dietary therapy, respectively.

CONCLUSIONS

Inconsistencies exist in the NCEP guidelines such that persons at low risk for the development of CHD are offered more intensive interventions than are other who actually are at much higher risks, and vice versa. Women in particular tend to be overtreated, relative to men. These findings point out the difficulties of promulgating guidelines that will appropriately match risk to preventive interventions in a complex multifactorial disease.

Dietary reduction of serum cholesterol concentration: time to think again

OBJECTIVE

To evaluate the long term efficacy of diets in lowering serum cholesterol concentration.

DESIGN

Descriptive overview of 16 published controlled trials of six months' duration or longer.

SETTING

Trials had been conducted in hospital clinics (6), industry (3), mental hospitals or institutions (3), and in general populations (4).

PATIENTS

Trials had been conducted in high risk subjects (5), in unselected healthy subjects (6), or for secondary prevention in patients with coronary heart disease (5). Women were included in only four trials.

INTERVENTIONS

Diets equivalent to the step 1 diet were employed in eight trials, with individual intervention by dietitians (3) or occupational physicians (2) or with population advice (3). Intensive diets which were more rigorous than the step 2 diet were employed in eight trials.

MAIN OUTCOME MEASURES

Net change in serum total cholesterol concentration in subjects receiving treatment with diet compared with values in control subjects after six months to 10 years.

RESULTS

In five trials with the step 1 diet as individual intervention the net reduction in serum cholesterol concentration ranged from 0% to 4.0% over six months to six years. In trials with population education reductions in cholesterol concentrations were 0.6-2.0% over five to 10 years. When population and individual dietary advice were combined changes in cholesterol concentration ranged from a fall of 2.1% to a rise of 1.0% over four to 10 years. Diets more intensive than the step 2 diet reduced serum cholesterol concentration by 13% over five years in selected high risk men in the population; by 6.5-15.1% over two to five years in hospital outpatients; and by 12.8-15.5% over one to four and a half years in patients in institutions.

CONCLUSIONS

The response to a step 1 diet is too small to have any value in the clinical management of adults with serum cholesterol concentrations above 6.5 mmol/l. Current guidelines recommend screening of serum cholesterol concentration in healthy subjects, followed by treatment with a step 1 diet. The guidelines should be reviewed to provide a more realistic estimate of the effect of a step 1 diet and of the likely need for lipid lowering drugs.

Screening for hyperlipidaemia in diabetes mellitus. Relationship to glycaemic control

Diabetic patients have an increased risk of developing cardiovascular disease which, in part, may be due to lipid abnormalities. Our aim was to establish from an initial screening programme what proportion of diabetic patients attending a routine diabetic outpatient clinic had hyperlipidaemia despite having good or acceptable glycaemic control. We screened 299 randomly selected diabetic patients to assess the prevalence of hyperlipidaemia and its relationship to glycaemic control. Twenty-eight per cent had hyperlipidaemia (defined as cholesterol greater than 6.5 mmol/L and/or non-fasting triglycerides greater than 3 mmol/L). Of these hyperlipidaemic patients, 71% had good or acceptable glycaemic control as defined by a glycated haemoglobin value of less than 10%. Approximately 40% of type 2 diabetic patients had body mass index values outside recommended targets indicating the potential of weight reduction in this group as a treatment modality. Our results indicate that the majority of hyperlipidaemic diabetic patients had good or acceptable glycaemic control, and as such these patients are potential candidates for specific lipid lowering therapy.

Cholesterol screening and life assurance

OBJECTIVES

To examine how insurance companies assess proposals for life assurance from applicants with raised cholesterol concentrations and to determine the excess mortality rating applied.

DESIGN

Survey of 49 companies underwriting term life assurance.

SETTING

United Kingdom.

SUBJECTS

Four fictional men aged 30 seeking 20 year term policies paying benefit only on death. Two had total cholesterol concentrations of 6.4 and 8.1 mmol/l but no other cardiovascular risk factors; one was overweight, hypertensive, smoked 20 cigarettes daily, and had a total cholesterol concentration of 8.1 mmol/l; and one had possible familial hypercholesterolaemia and a total cholesterol concentration of 10.7 mmol/l after treatment.

MAIN OUTCOME MEASURE

Percentage excess mortality rating.

RESULTS

All companies used explicit criteria to assess the mortality risk associated with hyperlipidaemias, and 47 companies applied the same criteria to men and women. No excess mortality rating was imposed on an applicant with a total cholesterol concentration of 6.4 mmol/l, but a small excess was applied to an applicant with a concentration of 8.1 mmol/l (median excess 50%, range 0-75%). When multiple cardiovascular risk factors were present the same concentration of 8.1 mmol/l resulted in a substantial excess (median 135%, range 50-200%). A smaller but more variable excess was applied to an applicant with possible familial hypercholesterolaemia (median 75%, range 0-200%).

CONCLUSIONS

Despite considerable differences among companies in the excess mortality ratings applied, increases in term life assurance premiums are likely to be restricted to patients with severe hypercholesterolaemia, in particular those with familial hypercholesterolaemia. In the absence of other cardiovascular risk factors milder hypercholesterolaemia is unlikely to result in higher premiums.

A heart health assessment programme in general practice in County Kilkenny, Ireland

The Kilkenny Faculty of the Irish College of General Practitioners and the Kilkenny Health Project have established a Health Assessment Programme (HAP) to standardise the examination and recording of coronary heart disease (CHD) risk factors in general practice. Criteria were agreed for classification and coding of demographic data, relevant medical history and risk behaviours. Height, weight and blood pressure are measured and venous blood sample is taken for total cholesterol estimation. The assessment is followed by appropriate counselling. The HAP was first targetted at men and women aged 40 to 49 years. During the first 16 months of the programme, 2102 assessments were carried out by 41 general practitioners, which represents 29% of the target group. Those taking part had a lower social class distribution when compared with participants in the KHP baseline survey in 1985. There were no significant differences between the two groups in smoking prevalence or in the distribution of body mass index. Median cholesterol was 5% lower in the HAP group than at the baseline survey. 16% of the HAP clients had diastolic blood pressures of 90 mm Hg or more. The HAP has demonstrated that it is feasible to measure CHD risk factors in a variety of general practice settings. The format facilitates a preventive orientation and has proved acceptable to patients.

Doxazosin: a study in a cohort of patients with hypertension in general practice--an interim report

The objective of this study was to assess the safety and efficacy of doxazosin in a substantial cohort of hypertensive patients drawn from general practice. A total of 4027 patients entered the study, 1472 of whom (36.6%) were untreated hypertensive patients. Patients were not advised to change diet, smoking habit, or life-style during the study. Twenty-one percent were cigarette smokers, and concurrent diabetes was present in 2.3%. Baseline blood cholesterol exceeded 200 mg/dl (5.2 mmol/L) in 90% and 250 mg/dl (6.5 mmol/L) in 56% of patients. The mean decrease in blood pressure produced by doxazosin was 22/15 mm Hg after 10 weeks of therapy; there was a mean decrease in heart rate of 1 beat/min. The mean maintenance dose for all patients was 3.1 mg/day. Side effects considered related or possibly related to treatment were reported in 705 patients. Treatment was discontinued in 233 patients (5.8%) because of adverse events related or possibly related to treatment with doxazosin. Doxazosin produced a significant (p less than 0.001) decrease in total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels and a significant increase in high-density lipoprotein cholesterol and the ratio of high-density lipoprotein:total cholesterol. The potential reduction in 10-year coronary heart disease risk (according to the Framingham equation) was calculated to be 20.4%.

Physicians' attitudes to the treatment of elevated serum cholesterol

A questionnaire was sent to 457 physicians (328 general practitioners, 129 hospital doctors) to assess their attitudes to and their knowledge and practice of the management of raised serum cholesterol. Replies were returned by 206 (63%) general practitioners and 95 (74%) hospital doctors. While smoking, hypertension, diabetes mellitus and elevated total serum cholesterol were recognised as major risk factors for coronary heart disease, a significant number of respondents considered serum triglycerides to be less important. Both groups of physicians start dietary management at similar total serum cholesterol levels, but hospital doctors were more likely to use dietetic services. The two groups had a similar threshold for the addition of drug therapy. A bile acid sequestrant was the favoured first choice as a cholesterol lowering agent, although a wide variety of other drugs were also chosen. The screening of high risk patients was preferred to whole population and opportunistic screening for identifying hypercholesterolaemic individuals. The findings have important implications in the delivery of services to hypercholesterolaemic patients.

Lipid screening: is it enough to measure total cholesterol concentration?

OBJECTIVES

To determine whether measurement of total cholesterol concentration is sufficient to identify most patients at lipoprotein mediated risk of coronary heart disease without measurement of triglyceride and high density lipoprotein (HDL) cholesterol concentrations.

DESIGN

Cross sectional screening programme.

SETTING

Six general practices in Oxfordshire.

PATIENTS

1901 Men and 2068 women aged 25-59.

MAIN OUTCOME MEASURE

Cardiovascular risk as assessed by fasting venous plasma concentrations of total cholesterol, triglyceride, and HDL cholesterol.

RESULTS

2931 Patients (74% of those screened) had a total cholesterol concentration of less than 6.5 mmol/l. If the triglyceride concentration had not been measured in these patients isolated hypertriglyceridaemia (greater than or equal to 2.3 mmol/l) would have remained undetected in 185. Among these 185 patients, however, 123 were overweight or obese and only 18 (0.6% of those screened) had an increased risk associated with both a raised triglyceride concentration (greater than or equal to 2.3 mmol/l) and a low HDL cholesterol concentration (less than 0.9 mmol/l). Conversely, in the 790 patients with predominant hypercholesterolaemia (cholesterol concentration greater than or equal to 6.5 mmol/l and triglyceride concentration less than 2.3 mmol/l) measurement of HDL cholesterol concentration showed that 348 (9% of those screened) had only a moderately increased risk with a ratio of total to HDL cholesterol of less than 4.5 and 104 had a low risk with a ratio of less than 3.5.

CONCLUSIONS

Fasting triglyceride and HDL cholesterol concentrations identify few patients at increased risk of coronary heart disease if the total cholesterol concentration is less than 6.5 mmol/l. HDL cholesterol and triglyceride concentrations should, however, be measured in patients with a total cholesterol concentration exceeding this value. Total cholesterol concentration alone may overestimate risk in a considerable number of these patients, and measurement of HDL cholesterol concentration allows a more precise estimate of risk. Measurement of the triglyceride concentration is required to characterise the lipoprotein abnormality. A patient should not be started on a drug that lowers lipid concentrations without having had a full lipoprotein assessment including measurement of HDL cholesterol concentration.

Placebo-controlled trial of the effects of guar gum and metformin on fasting blood glucose and serum lipids in obese, type 2 diabetic patients

Nineteen obese patients with Type 2 diabetes mellitus were treated for periods of 3 months with placebo, guar gum (5 g three times daily) and metformin (500 mg three times daily) in a randomized double-blind, double-placebo, cross-over study. Both active agents decreased fasting blood glucose from 11.4 +/- 3.7 mmol l-1 (mean +/- SD) to 8.6 +/- 2.8 mmol l-1 on metformin (p less than 0.001) and to 9.5 +/- 3.9 mmol l-1 on guar gum (p less than 0.01). Metformin significantly reduced the very low density lipoprotein (VLDL) cholesterol concentration from 0.62 (+0.73, -0.34) mmol l-1 (geometric mean (+SD, -SD)) to 0.43 (+0.58, -0.25) mmol l-1, (p less than 0.02), but unless hyperlipidaemia was present there were no changes in other serum lipid or lipoprotein levels. In patients with serum cholesterol greater than 6.5 mmol l-1 decreases in serum triglycerides from 3.29 (+3.27, -1.64) to 2.46 (+2.55, -1.25) mmol l-1 (p less than 0.02) occurred with metformin. In these patients guar gum produced a reduction in serum cholesterol (from 7.70 +/- 0.90 to 6.41 +/- 1.11 mmol l-1, p less than 0.01) due to an effect on low density lipoproteins. These differential effects may be important in planning therapy when hyperlipidaemia accompanies Type 2 diabetes.

The Vale of Leven health promotion project

A two stage health promotion programme is in progress in the Vale of Leven in Dunbartonshire. The first stage has been completed within a local factory (Polaroid UK Limited), the largest private employer in the district. A total of 1205 employees, representing 87% of the workforce, took part in the programme and were initially screened for coronary artery risk factors. Blood pressure, serum cholesterol, body composition and aerobic fitness were measured and smoking habits determined. Aspects of lifestyle were assessed by questionnaire. All employees whose initial cholesterol concentration was greater than 6.5 mM were given simple dietary advice and their cholesterol concentration thereafter remeasured. Eighty-two per cent of these men and 72% of these women succeeded in reducing their cholesterol, the men by a mean of 1.3 mM, the women by a mean of 0.7 mM. The health initiatives undertaken within the factory at the same time as screening are also described in this paper.

Within-clinic reagent strip lipid measurement

The agreement between the Reflotron dry chemistry analyser and laboratory methods for measurement of total cholesterol and triglycerides was assessed by studying the between-method variability for individual samples. A paired comparison of replicate measurements from venous blood was made for 105 cholesterol and 90 triglyceride specimens. There was no significant mean difference between the two methods for cholesterol measurement (difference 0.02 mmol l-1, 95% Cl -0.07 to 0.10 mmol l-1) but there were wide limits of agreement (+/- 2SD) of -0.87 to 0.90 mmol l-1. Some of the differences in measurement were large enough to be clinically misleading and would result in inconsistencies in diagnostic assignment between the two methods. Both methods achieved relatively poor repeatability which limited the agreement possible (coefficient of repeatability, defined as 2SD of the differences, 0.59 mmol l-1 for the Reflotron and 0.38 mmol l-1 for the laboratory). The repeatability of triglyceride measurement was similar for the Reflotron and laboratory (coefficient of repeatability 0.24 mmol l-1 and 0.27 mmol l-1, respectively). However, there was a significant systematic difference between methods, with the Reflotron reading 0.30 mmol l-1 less than the laboratory method (95% Cl 0.26 to 0.35 mmol l-1) and the limits of agreement between the methods were -0.09 to 0.70 mmol l-1. It is important that clinicians recognize the limits of agreement between dry chemistry analysers and laboratory methods and take these into account when using them to screen for hyperlipidaemia or to monitor treatment of hyperlipidaemic diabetic patients.

Attitudes and practices of primary care physicians in the management of elevated serum cholesterol levels

We conducted a telephone survey of 102 randomly selected Ottawa family physicians to determine their attitudes and practices regarding the treatment of hypercholesterolemia. Of the 102, 56% routinely measured serum cholesterol levels in all their patients over the age of 30 years, and 24% did so for patients in more restricted age ranges. The level at which they started dietary therapy averaged 6.95 mmol/L (270 mg/dl); for 25% it was less than 6.22 mmol/L (240 mg/dl). The level at which they started drug therapy averaged 8.9 mmol/L (345 mg/dl); for only 15% was it 7.23 mmol/L (280 mg/dl) or less. Two-thirds were unable to give numerical values to the serum cholesterol levels at which they started diet therapy, and 38% used the upper limits of laboratory normal values as an indication to start therapy. Our findings contrast markedly with results reported for US family physicians, who treat hypercholesterolemia much more aggressively. The variability in practices must be addressed if public campaigns to lower serum cholesterol levels are to be undertaken.

Who should have their cholesterol concentration measured? What experts in the United Kingdom suggest

General practitioners are being encouraged to participate in preventive care, including preventing coronary heart disease. Now that they can measure cholesterol concentrations in their surgeries they need to decide which patients should be screened. Several reports on measuring cholesterol concentrations in the United Kingdom were reviewed to see if experts agreed about who ought to be screened. The results showed that currently no national consensus exists, making it difficult for general practitioners to plan policies for their patients.

Essential data derived from biological variation for establishment and use of lipid analyses

The analytical and biological components of variation of total cholesterol, high density lipoprotein (HDL) cholesterol, HDL3 cholesterol, HDL2 cholesterol and apolipoproteins A-I and B in serum were assessed in 12 apparently healthy individuals. All analytes showed marked individuality and therefore conventional population based reference intervals are of little use. The differences required for serial results to have changed significantly for these assays were calculated. The data presented confirm that the assays studied have limited value in screening the general population.

Quality of plasma cholesterol measurements in primary care

Three surveys were made of the quality of plasma cholesterol measurements performed with a commercial desktop analyser (BCL Reflotron) in primary care. Each survey included three specimens, and results were received from 37, 61, and 69 participants. Although many participants obtained satisfactory results, 8.6% of the results differed by 1.0 mmol/l or more from the target values, and the overall between instrument dispersion of results was 1.3 times that between hospital laboratories. It was found that common sources of error were poor technique and the use of outdated reagent strips. Users of such instruments outside the laboratory need help and advice with training, and guidelines for this are provided. The main recommendations are that users should establish contact with a local clinical chemistry laboratory for training and support and should participate in external quality assessment schemes.

Prevention of cardiovascular disease by psychological methods

It is generally recognised that much cardiovascular disease is the result of voluntary behaviour such as smoking cigarettes, and the pursuit of stress-prone lifestyles. Since these risks are primarily behavioural, it is appropriate to attempt to alter them, and hence reduce the risk of cardiovascular disease, using psychological methods, and such methods can reduce both biological and psychological stress-related factors. Studies of healthy populations, of those at increased risk, and of patients with clear cardiovascular disease have all shown that risk-related behaviour can be altered and, in some cases, the incidence of cardiovascular disease reduced. Future research will have to extend these findings, which were often on atypical populations, and confirm reduction of cardiovascular disease.