Dr Mark Wood explains how his practice tackled the problem of putting the SMAC guidelines on cholesterol lowering into effect
Once in a while a paper hits the medical press that turns accepted practice on its head. In late 1994, The Lancet published such a paper – the Scandinavian Simvastatin Survival Study, known as 4S.1
Overnight, 4S converted cholesterol sceptics around the globe, including me, into primary care cardiovascular zealots. The results of the trial are now part of the fabric of modern medicine. It is worth revisiting the key results, however, to remind ourselves of the bedrock upon which all the subsequent work is based.
A total of 4 444 men and women aged 35-69 years, with pre-existing ischaemic heart disease (previous myocardial infarction [MI] or confirmed angina) and cholesterol levels between 5.5 and 8.0mmol/l, were randomised to treatment with 20mg simvastatin per day or placebo. The median follow-up was 5.4 years.
The trial showed that in established coronary artery disease where cholesterol was moderately raised, the use of the HMG co-A reductase inhibitor simvastatin led to:
- A reduction in all-cause mortality; relative risk reduction (RRR) = 30%
- A reduction in coronary death; RRR = 42%
- A reduction in all coronary events; RRR = 30%
Further results are shown in Table 1.
Table 1: Summary of the 4S results
|NNT = numbers needed to treat; RRR = relative risk reduction|
It was clear that the sands were shifting. By the beginning of 1996 the reflective phase – that euphemism for inertia – was drawing to a close, and our partnership came to the realisation that we had to put theory into practice.
An indication of the size of the task facing us can be gleaned from a cursory look at our prescribing data from December 1994. On the eve of the publication of 4S, our practice of 15000 patients was prescribing statins of any kind to just nine patients. This represents a coverage of 0.13% of the 35-69 years cohort, the group covered by 4S.
We therefore considered how we might rectify this situation effectively. A debate ensued regarding the relative merits of opportunistic 'catch up' versus a planned, nurse-run clinic. Medicine is crawling with laws of halves, but here is another to add to the collection, which I shall call Wood's Law.
Only half the target group will be identified opportunistically by the hard-pressed GP, and half the time he/she will be too busy to address the issue. Only half of those patients will comply effectively (because they attended for a sore throat/ menorrhagia/a housing letter etc); and, of these, half will be lost to meaningful follow-up. It was to avoid Wood's Law that we decided to institute a nurse-run clinic.
The moment we embarked on a structured approach, the immediate challenge was how to define which patients we should treat. Having opted for a computer-driven nurse-run clinic, it took nearly a year to put in place the organisation and the computer programming.
Throughout 1996 we grappled with the question of what to measure (cholesterol or LDL) and what level to regard as requiring treatment. A major concern at this point was the potential for breaking the prescribing bank.
Then, in spring 1997, the Standing Medical Advisory Committee (SMAC) issued its guidance – a piece of work that we found invaluable in setting our parameters. The SMAC document recommends targeting all patients with a calculated annual risk of a coronary event of 3% or more.2 This includes the three groups shown in Table 2 (below).
Table 2: SMAC target group definitions and average sizes
|Percentage of the practice population aged 35-69 years|
|4.8% (1 and 2 combined)|
|3||No disease, high risk||
|LDL = low density lipoprotein; MI = myocardial infarction; SMAC = Standard Medical Advisory Committee|
After vigorous debate, the practice decided that the logistical problems of identifying the third group meant that primary prevention was not feasible. The identification of high-risk individuals with no personal history of ischaemic heart disease was felt to be too hit and miss to provide a robust group for intervention. There is no doubt that the drug cost of intervening in the primary prevention group was another factor that militated against us targeting this subset of patients.
On the final analysis we decided to focus exclusively on secondary prevention. We have therefore addressed SMAC groups one and two, but not group three.
The question of higher risk primary prevention is still an area for debate, and may need to be reviewed as and when we can be more confident about our database related to family history, diabetes, hypertension and smoking. As I write this, we are preparing a similar clinic for our diabetic patients.
Identification of the post-MI population was simple enough, although we had problems agreeing reliable search criteria for our angina group. What seemed like a simple enough Fask turned up more confounding factors than we ever thought possible. After a number of dry runs, we found that searching for patients who were taking nitrates provided the most reliable results.
These patients were entered into the protocol detailed below. We run the EMIS computer system within the surgery, and took advantage of the system's user definable protocol tool. This allowed us to write sub-routines along the lines of the tasks defined in the protocol, which could be translated into our own ischaemic heart disease clinic programme.
|Protocol for the use of statins|
This was run by our senior practice nurse in a dedicated ischaemic heart disease clinic, which took place for 2 hours each week for 18 months. This was the time required to process all the patients in the target group. From the outset it was envisaged as a 'catch up' clinic with a defined and finite workload. Ongoing management of newly diagnosed patients is left to the individual doctor.
Patients were invited by standard letter, and the nurse time was funded by an innovative collaboration with a pharmaceutical company. Opportunistic tetanus administration raised additional funds.
As can be seen from the protocol, the statin of choice for us was simvastatin. This decision was taken on the basis that its use was underpinned by the results of 4S. We had prolonged discussions regarding cost and the possibility of cheaper or more cost-effective alternatives. The overwhelming feeling, however, was that we should stick with the evidence presented in the landmark paper.
Table 3 shows the results of the clinic. A review carried out at one year found that dietary advice alone made no difference to cholesterol levels.
Table 3: Clinic results
|Practice population aged 35-69 years||6905|
|Expected target group size||331 (4.8%)|
|Our target group size (invited)||281 (4.06%)||164||117|
The protocol had initially included a 3-month trial of diet, and an extra visit to the nurse as a result. After the review we deleted this from the system. Patients were still given dietary advice, but were started on their statin as soon as the need became apparent.
Most people's great concern about treating cholesterol levels in these patients is the cost. We found, however, that by tightly targeting the use of statins, large increases in the drug budget were avoided.
The clinic has added an extra £20 000 to our annual drug budget. This was totally offset by a parallel initiative to move patients with gastro-oesophageal reflux disease from omeprazole 20mg per day to omeprazole 10mg per day.
With 103 patients now taking statins as a result of our clinic, we can calculate, from the data on numbers needed to treat (NNT), how many events we are now preventing. The ongoing treatment initiated by this clinic now prevents one cardiac event every 8 months, and one death every 17 months.
This saves countless thousands of pounds in secondary care cardiac services – even if this saving is invisible. And the savings in human terms are immeasurable.
- Scandinavian Simvastatin Survival Study (4S). Lancet 1994; 344: 1383-9.
- SMAC Guidelines on the Use of Statins. May 1997.