26 MARCH 1977

two specialists in community medicine, and one each from the specialties of child psychiatry, clinical child health, epidemiology, general practice, and general surgery. Other health professions contributed two nurses and a dental surgeon. Social work and education were each represented by two members and there was one psychologist. The membership of the committee was completed by three "consumers" of the child health services in the form of mothers. Neither quantitatively nor qualitatively can it be sustained that the unanimous recommendations were influenced unduly by paediatricians. Instead of tilting at windmills Dr McLuskie might care to reflect on the reasons why persons representing the wide variety of knowledge and experience evident in the Court Report came to propose the general practitioner paediatrician. THOMAS E OPPE Paediatric Unit, St Mary's Hospital Medical School, London W2

Committee on Child Health Services, Fit for the Future. London, HMSO, 1976.

Fibrinolytic activity in health and vascular disease

SIR,-The actual differences in fibrinolytic activity between normal subjects and patients with vascular disease in the study by Professor N L Browse and others (19 February, p 478) are almost certainly fewer and less marked than those reported. The 294 patients with vascular disease (in eight groups), whose mean age was about 54, have been compared with 32 normal ambulant subjects with a mean age of 29-2 rather than with 88 "healthy" inpatients admitted for surgery for local disease, whose mean age was 56-4. The difference in mean resting lysis times between the normal ambulant subjects (256 min) and the "healthy" inpatients (370 min) is highly significant; it is attributed to the physical inactivity of the latter group rather than to the age difference since regression analysis within the 88 "healthy" inpatients showed no age effect. In our view, however, the 32 normal ambulant subjects form an inappropriate comparison group on the grounds both of their age and of their level of physical activity. Dealing with age, the table printed below shows age-specific lysis times,' fibrinolytic activity, and fibrinogen levels2 in over 1500 subjects in our prospective study of arterial disease. (We define fibrinolytic activity as 100/lysis time in hours and use it in preference to lysis time because (1) it gives a direct rather than an inverse measure of activity and (2) it is approximately normally distributed, unlike lysis time.) It was not until we had recruited about 300 men that the age effect became apparent. Fibrinolytic activity is subject to

such considerable within-person variability3 that it is most unlikely that any age effect would show up in as few as 88 patients, especially as 32 were women, in whom the age effect, if any, is very much less than in men. Although the age effect can be detected only if large numbers are studied, it is essential to allow for it (including the rise in fibrinolytic activity in men over 55, which follows the fall seen in those aged 18-54) when comparing mean values in different groups. The same consideration applies to plasma fibrinogen values, although these rise with age in both men and women. Because of the age effect the use of the younger normal ambulant subjects as a comparison group will inevitably lead to greater differences between those with and those without vascular disease than are actually the case. Professor Browse and his colleagues suggest that the differences in physical activity between the normal ambulant subjects and "healthy" inpatients could be responsible for the differences in mean lysis times. The evidence they cited was an experiment in which healthy volunteers were subjected to moderate exercise.4 However, even if physical activity levels are responsible for the differences in lysis time it would surely have been more logical for them, on their own reasoning, to compare the groups of patients with vascular disease with the "healthy" inpatients since the physical activity levels of these two groups at the time of study were almost certainly more similar to each other than they were to those of the normal ambulant subjects. There is little doubt that fibrinolytic activity is decreased in patients with manifest vascular disease,5 but as interest in this topic increases it is important to be aware of, and where possible to allow for, the effects of age, sex and other relevant variables.


of seat belts compulsory and thus reduce the horror for individuals, families, and society was rejected by Parliament last year and is unlikely to become law this year because of shortage of parliamentary time. As a result Britain is likely to be one of the last of the technically developed countries to make the use of seat belts compulsory by law. Meanwhile yet again parliamentary time is to be spent debating amendments to the abortion law, amendments which a large proportion of the medical profession feel will not in any way improve the functioning of the law in terms of relief of human suffering, medical safety, efficiency, or equality of service throughout the country. By all means give thought and time to consideration of the way the abortion law is working. Having led the way in liberalising the abortion law we should be ever watchful that it is functioning in the best interests of the country and the individual. The Lane Committee has spent a long time doing just this and implementation of its recommendations' would do all that is needed to safeguard the individual and society in this matter. But let us also give time for legislation to bring in a law that would do much to reduce the loss of life, brain injury, and spinal injury in the wageearning sector of our society resulting from road traffic accidents-surely as great a cause for concern in terms of human suffering and as great a burden on medical resources and manpower. The medical profession should influence parliamentarians to use their time wisely. BARBARA L TONGE Chester

Report of the Committee on the Working of the Abortion Act, London, HMSO, 1974.

T W MEADE R CHAKRABARTI Preventing thromboembolism after W R S NORTH myocardial infarction MRC-DHSS Epidemiology and Medical Care Unit, SIR,-I was interested to read the article by Drs P A Emerson and P Marks (1 January, Northwick Park Hospital, Harrow, Middx p 18) and their finding that low-dose sub1 Fearnley, G R, and Chakrabarti, R, Lancet, 1962, 2, cutaneous heparin significantly reduces leg 128. vein thrombosis after myocardial infarction. 2 Feamley, G R, and Chakrabarti, R, Lancet, 1966, 2, However, I was unable to find the dose of 757. 3 Meade, T W, and North, W R S, British Medical heparin used by these workers. Is the dose of Bulletin. In press. heparin given subcutaneously in this situation 4 Ogston, D, and Fullerton, H W, Lancet, 1961, 2, 730. 5Konttinen, Y P, in Fibrinolysis. Finland, Oy Star Ab, so well known and standardised that it need 1968. not be mentioned ? A J RICHARDS Priorities in legislation Department of Rheumatology,

SIR,-As you state in your leading article (1 January, p 2), the risk of being killed in a road accident is increased about four times for someone not wearing a seat belt; the risk of serious injury is also proportionately greater. In spite of these facts a Bill to make the wearing

Worthing Hospital, Worthing, Sussex

SIR,-The paper by Drs P A Emerson and P Marks (1 January, p 18) does not mention how long their patients were confined to bed after myocardial infarction. There is considerable evidence from several centres, including our own,1 that a short period of immobilisation Northwick Park Heart Study. Mean lysis times (hours), fibrinolytic activity (100/lysis time), and plasma is associated with a low incidence of venous fibrinogen levels (gll) by age and sex; 1068 white men and 488 white women not on oral contraceptives thromboembolic complications. Since Drs Emerson and Marks recommend that nonAge (years) smokers "should be given low-dose heparin -49 -54 -59 -39 -44 18-24 -29 -34 -64 All ages subcutaneously" it would be helpful to have this information in case their period of bed 6-5 6-0 55-49 7-2 5-2 5-7 5-2 Men* 3-6 4-5 5-6 Lysis time af Women 4-5 3-4 6-5 4-5 4-3 5-1 5-1 5-7 rest is more prolonged than is common in 30-6 34-5 32-7 27-8 27-1 25-0 23-9 26-7 Fibrinolytic JMen* 27-6 28-2 most centres. 26-1 30 3 27-5 29-0 35-0 30-1 26-8 28-8 Women activity 28-6 Men* 2-314 2-442 2-425 2-612 2-693 2-891 3-019 3-076 3-089 2-733 Only one of their 81 patients died during the Fibrinoge Fibrmnogen f Women* 2-365 2-351 2-652 2-824 2-799 2-823 3-038 3-255 2-882 two weeks of the study. This is a strikingly low mortality compared with the 10-20 % reported *Significant change with age. from most coronary care units. This extraConversion: SI to traditional units-Fibrinogen: 1 g/l = 100 mg/100 ml.

Fibrinolytic activity in health and vascular disease.

BRITISH MEDICAL JOURNAL 26 MARCH 1977 two specialists in community medicine, and one each from the specialties of child psychiatry, clinical child h...
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