Norma Bell and Dr Mike Jones describe an audit that clarified the care and management of patients with raised cholesterol for many practices in Stockport
Stockport GPs are among the highest prescribers of lipid-lowering drugs in the country. A number of possible explanations for this have been proposed:
The success of its coronary heart disease (CHD) risk factor screening programme
Stockport has had a CHD risk factor screening programme since 1989. At the age of 35 and on every subsequent quinquennial birthday, individuals are invited to attend their practice for screening for CHD risk factors. If two or more risk factors are found, the protocol directs that cholesterol be measured, which means that in Stockport practices more hypercholesterolaemia is uncovered.
A high standard of local general practice, all involved in CHD screening
Stockport has two full-time facilitators whose remit includes practice nurse education in health promotion and chronic disease management.
Local cardiologists with a particular interest in preventive medicine
|Two local university lipid clinics led by consultants with specialist interests|
|The targeting of Stockport by drug companies for intensive marketing?|
Something unique about the local population?
Stockport lies south of Manchester in the north-west of England It has a predominantly white population and only small ethnic minority groups.
In 1995, on completion of the audit, the standardised mortality rate (SMR) for ischaemic heart disease (IHD) was slightly higher than the national rate, but lower than the rate for the North West Region (Table 1). These figures were confirmed by the number of deaths per 100000.1 Within Stockport there are large variations in SMR, ranging from 246 in an inner-city area to 50 in an affluent suburb.
Table 1: Comparison of standardised mortality rates (SMRs) for ischaemic heart disease in various parts of the country
|Ischaemic heart disease||
Deaths per 100 000
|North West Region||
|Figures from the Public Health Common Data Set 1995, covering data mainly for the year 1994|
A retrospective audit was carried out in Spring 1995 with the general aim of establishing whether practices were adopting intervention and management protocols in keeping with the British Hyperlipidaemia Society Guidelines. Specifically, with limited resources, efforts should be concentrated on high priority groups.
|Have patients known to have IHD, whose cholesterol level has been found to be >5.2mmol/l, received appropriate lifestyle advice, and has treatment with lipid-lowering drugs been initiated where necessary?|
|Have patients not known to have IHD, whose cholesterol level has been found to be >6.5mmol/l, received lifestyle advice and/or lipid-lowering drug treatment, if necessary?|
Identical audits were performed on two groups of patients: those with IHD and those without (non-IHD). The British Hyperlipidaemia Society Guidelines were used as targets.
Practices were asked to select randomly 20 patients per GP from each group of patients and complete a data collection sheet. Randomisation was achieved in one of two ways: computer generated and systematic sampling.
Data were received from 33 practices (56% of Stockport's practices, representing 87 Stockport doctors).
There were 3471 patients in our database at the end of the audit: 1737 individuals with existing IHD and a pretreatment cholesterol level >5.2mmol/l and 1734 without IHD with a cholesterol level >6.5mmol/l. (Data sheets from nine patients were either icomplete or incorrectly completed and could not be included.)
Comparative data are shown in Figures 1 and 2. The wide differences between practices were not fully explained by demographic differences, but those patients attending a practice where the primary healthcare team had a particular interest in cardiovascular disease were likely to fare uniformly better.
|Figure 1: Percentage of patients with IHD who reached the target of <=5.2 mmol/l cholesterol in the 33 individual practices|
|Figure 2: Precentage of patients without IHD who reached the target of <=6.5 mmol/l cholesterol in the 33 individual practices|
1. Was the need for treatment/ advice based on a fasting lipid profile?
In those patients with IHD, 80% of the decisions to prescribe lipid-lowering drugs were based on a fasting lipid profile, with the remaining 20% based on a total cholesterol only.
2. Had the effects of intervention been monitored?
For 452 (26%) of the IHD patients and 604 (35%) of the non-IHD patients only one reading was available, so these patients could not be included in the statistical analysis.
There would appear to be two possible explanations for these figures:
|Some patients may have been identified when insufficient time remained in the audit period for a follow-up lipid profile to be taken.|
|Patients may have been identified as having a raised lipid profile some time previously, but no follow-up profiles were taken (i.e. the patient was left unmonitored).|
The extent of this problem was an unexpected and important finding and has been made the subject of further audits in many of the practices. Since the audit a great deal of work has been done specifically around constructing disease registers and protocols for patients with IHD to standardise and monitor their care.
3. How long was dietary treatment alone given before drug treatment was initiated?
Drug treatment was initiated:
|Immediately in 17% of patients (i.e. no dietary trial)|
|After 3 months' dietary treatment in 14% of patients|
|After 6 months' dietary treatment in 16% of patients|
After 12 months or more dietary treatment in 36% of patients
(No data were available in 17% of cases.)
As a result of the audit, many practices have adopted protocols incorporating algorithms that standardise their approach to care, including when to take fasting lipid profiles, how long to persevere with dietary treatment and when to initiate drug treatment.
4. Had the appropriate class of drug been prescribed?
Since this audit the therapeutic picture has become much clearer and clinicians' knowledge of prescribing has improved. Our lipid advisor felt that the appropriate class of drug had been prescribed in 56% of cases.
This assessment was based on the premise that if the problem was mainly a raised low density lipoprotein (LDL) level, with fairly normal triglyceride levels, then the drug of choice would be either a statin or a resin.
However, if the dyslipidaemia was predominantly an excess of triglycerides then fibrates would be the drug of choice. This assessment was based on the general consensus of what was considered to be best practice at the time of the audit (1995).
5. Were other risk factors assessed appropriately?
|84% of patients received dietary advice|
|100% of patients had their blood pressure measured|
|94% of patients had their smoking status recorded|
|77% of patients had their family history recorded|
70% of patients had their body mass index (BMI) recorded
We felt that this indicated a good level of care, comparing favourably with the hospital-based ASPIRE study where 65% of patients had a record of being given dietary advice, 95% had their blood pressure recorded, 88% had their smoking status recorded, 79% had their weight recorded but only 65% of those with a BMI >30 received dietary advice.2
In this study population, there was a 9% reduction in cholesterol level in those patients given diet advice, which was considerably higher than has been found in other studies. Most other studies have suggested that the extent to which cholesterol reduction may be expected using a lipid-lowering diet is in the region of 3-5%.3-5
One study, however, did concur with our findings, demonstrating a fall of 9% in the cholesterol level of post myocardial infarction patients following a lipid-lowering diet.6 The authors concluded that the participants in this trial were more motivated to follow strict diets.
This was one of the possible explanations that we considered for the results observed in our audit, since patients were not randomly selected to have their cholesterol taken, but were individuals who were motivated to attend for cardiovascular screening or had been diagnosed with IHD and may have been more motivated to change their behaviour in response to advice. This figure is encouraging as it shows what it is possible to achieve in a primary care setting.
sUMMARY OF RESULTS
|Only 14% of patients with IHD reached the target cholesterol level of 5.2mmol/l|
|Only 37% of patients without IHD reached the target cholesterol level of 6.5mmol/l|
|28% of the patients with IHD were on lipid-lowering drugs|
|14% of the patients without IHD were on lipid-lowering drugs|
|Where lipid-lowering drugs were used, a 20% reduction in cholesterol level was achieved|
|Where diet advice alone was used as an intervention, a 9% reduction in cholesterol level was achieved|
Stockport GPs remain some of the highest prescribers of lipid-lowering drugs in the country. This audit, however, found no evidence of indiscriminate prescribing. On the contrary, the figures were quite alarming, given that the practices which took part may have considered themselves to be proficient at treating hyperlipidaemia, producing a sample bias.
There is overwhelming evidence that in both primary and secondary prevention, reducing the cholesterol level considerably lowers the risk of cardiovascular disease,7 and in these trials the lipid-lowering drugs had a very low incidence of serious side-effects.8–11
áince this audit the guidelines have changed and lower levels of cholesterol are now recommended. In particular, LDL is targeted, and a multiple risk factor approach to include the total cholesterol/high density lipoprotein ratio is used in the overall (ssessment of risk of developing cardio-vascular disease. These are quoted as percentage risks over a period of time, e.g. 30% risk of developing cardiovascular disease in a 10-year period, i.e. 3% over a 1-year period. The Oevels accepted by various health authorities will be an economic decision.
This audit provided the incentive for many practices to improve the care and management of patients with raised cholesterol. This included the implementation of disease registers for those with IHD and the adoption of protocols for their management. Becmuse of budget constraints the focus has been on secondary prevention and a re-audit is currently under way.
- Eighth Annual Public Health Report for Stockport. Part II Annual analysis. 1996: 262.
- ASPIRE Steering Group. A British Cardiac Society survey of the potential for secondary prevention of coronary heart diesease: ASPIRE (Action on Secondary Prevention through Intervention to Reduce Events) principal results. Heart 1996; 75: 334-42.
- Neil HA W, Roe L, Godlee RJ et al. Randomised controlled trial of lipid lowering advice in general practice: the effects on serum lipids, lipoproteins, and antioxidants. Br Med J 1995; 310: 569-73.
- Elbrahim S, Davey Smith G. Systematic review of randomised controlled trials of multiple risk factor interventions for preventing coronary heart disease. Br Med J 1997; 314: 112-17.
- Brunner E, White I, Thorogood M et al. Can dietary interventions change diet and cardiovascular risk factors? A meta-analysis of randomised controlled trials. Am J Pub Health 1997; 87: 1415-22.
- Ebrahim S, Davey Smith G. Health Promotion in Older People for the Prevention of Coronary Heart Disease and Stroke. London: Health Education Authority, 1996.
- Law MR, Wald NJ, Wu T, Hackshaw A, Bailey A. Systematic underestimation of association between serum cholesterol concentration and ischaemic heart disease in observational studies: data from the BUPA study. Br Med J 1994; 308: 363-6.
- Scandinavian Simvastatin Survival Study Group (4S). Lancet 1994; 344: 633-8.
- Shepherd J, Cobbe SM, Ford I et al. Prevention of Coronary Heart Disease with Pravastatin in Men with Hypercholesterolaemia (WOSCOP). N Engl J Med 1995; 333: 1301-7.
- Sacks F, Pfeffer M, Moye L et al. The effects of pravastatin on coronary events after myocardial infarction in patients with average cholesterol levels. CARE. N Engl J Med 1996; 335: 1001-9.
- The Lipid Study Group. Design features and baseline characteristics of the LIPID (Long-term Intervention with Pravastatin in Ischaemic Disease Study): a randomised trial in patients with previous acute myocardial infarction and/or unstable angina pectoris. Am J Cardiol 1995; 76: 474-9.