SEMICONTINUOUS SCREENING OF A WHOLE COMMUNITY FOR HYPERTENSION

Saturday SEMICONTINUOUS SCREENING OF

A

WHOLE COMMUNITY FOR HYPERTENSION

J. TUDOR HART General Practitioner,

Glyncorrwg Health Centre, Port Talbot,

Glamorganshire

Screening for hypertension of 98% of an industrial village population (476 men and 436 women) aged 20-64 is described. The work was done within the normal framework of general practice in the National Health Service; the additional workload was measured, and no overall increase occurred either in home visits or health-centre consultations. Blood-pressures were read by a single observer whose systematic error was known, and are reported with means and standard deviations by 5-year age-groups. By defined criteria 26 men and 12 women required consideration for treatment (3·6% of men under 40, 7·0% of men aged 40-64; 0·5% of women under 40, 4·6% of women aged 40-64). Of those in the defined hypertensive group without symptoms, 9 out of 14 men and 3 out of 5 women had objective signs of heart or kidney damage by simple tests. It is concluded that screening for hypertension, using these criteria, is feasible with existing resources, and that high response-rates can be achieved with little difficulty if the procedure is carried out within the community by its own health workers. In an industrial workingclass population with a health service such as that in the United Kingdom, it is likely that, in the absence of screening, about half the cases of hypertension which may need treatment will be missed over a seven-year

1

August

1970

of reasonably acceptable and effective treatment for non-malignant hypertension. The level of sustained systolic or diastolic pressure which justifies reduction in the absence of symptoms or signs of organ damage is not agreed. Pickering 11 has proposed the following minimum levels of sustained diastolic pressure for this purpose: era

Sum ary

period. Introduction

TREATMENT of asymptomatic hypertension has been shown to reduce mortality and morbidity from stroke (but not, so far, from ischsemic heart-disease) in men and women under 65, both in uncontrolled community studiesand in controlled trialS.2,3 Smirk4 showed that the improvement in prognosis in retinal grade I and II hypertension depended on the prevalence of complications at the start of treatment. There has been some interest in identifying asymptomatic cases before the onset of complications, but efforts so far reported have been subordinate parts of multiphasic screening programmes. Even when conducted within general practice, these have given low response-rates, nowhere exceeding 50% so far as I know,5-8 though Hodes 9 seems to be aiming at 100% response over a five-year period. No epidemiologist would be satisfied with less than 85%; why should community screening aim any lower? A complete distribution of casual blood-pressures in a general practice has been reported by Fry,to but his actual distribution by agegroups was not published, and the work preceded the 7666

He derived these figures from Bechgaard’s data,12 as those associated with a mortality two and a half times the normal rate for age. In the valleys of Glamorgan, mortality from ischaemic heart-disease in men aged 35-44 is 75% above the England and Wales rate, and mortality from stroke in men aged 35-64 is 50% above the England and Wales rate. 13 There is no evidence that our blood-pressures differ from those elsewhere in Britain 14 ; but, as both these causes of death have been shown by many prospective studies to be more closely related to blood-pressure than to any other known risk factor, special effort to identify and treat high-risk cases in this area seems to be justified. This paper reports an attempt to extend the ordinary records of casual blood-pressure kept by any family doctor to cover all patients without exception, using Pickering’s criteria to identify those who might benefit by treatment; and to do this with the normal resources of National Health Service general practice. Material and Methods

Glyncorrwg is a small mining village in South Wales; population is stable, compact, and separated from the next village by 211z miles of road, and from everywhere else by mountains. All but 8 families are on my list. The population defined for this paper was all the men living in the Glyncorrwg ward of the Glyncorrwg urban district for three months or more during the year 1968, aged 20-64 in that year, who were on my list; and all the women on the same criteria, but based on the year 1969. Subjects who died or left the area during these years were retained. 9 men and 7 women in this age-group in the village were on its

other doctors’ lists. All blood-pressure measurements followed the technique used by Miall. 14 Readings were taken from the left arm with the subject seated, after a wait of five to thirty minutes. A 23 x 13 cm. cuff with nylon-hooklet binding was used, with a mercury sphygmomanometer. Pressure was raised rapidly to 200 mm. Hg and lowered at a steady rate of 2 mm. per second. Pressures were read to the nearest 5 or 10 mm. below the observed figure; no correction has been applied for this in reporting the results. Diastolic pressure was defined as that at which muffling of sounds preceded their disappearance (phase 4). The point of disappearance (phase 5) was unfortunately not recorded. 2 cases were already under treatment when I took over the practice in 1962, and for these the last two hospital readings before treatment were used. All the other R

224

separate estimations of

measurements are

by a single observer, and all the pressures pre-treatment pressures. Screening began in 1968; male ages are calculated for that year, and female ages for 1969. About half the men, and about a third of the women (excluding readings in pregnancy), had one or more readings already recorded by me since 1963. Pressures recorded when a subject was febrile or physically or mentally distressed were discarded, but those taken during minor coughs and colds were included. Advantage was taken of as many doctor-patient contacts as possible to accumulate two casual readings for each man and one for each woman. Where several readings were available, the most recent were taken. When about 10% were outstanding, invitations to attend the health centre were delivered; about a third responded within a month. Those still outstanding were visited at home. This involved 212 extra home visits (including revisits when the

glucose, and

are

cholesterol.

subject was out) spread over eighteen months, representing 5% of all visits during this period; but the visiting-rate per patient per year was 1-2 and 1-1in the two survey years, compared with 1-3 and 1-1in the two preceding years. The

symptomatic screening.

increase in health-centre consultations

was not

two

serum urea

and

My own error in measuring blood-pressure was rated against the London School of Hygiene training tape," and showed a mean error of +2-0 mm. in systolic pressure and +6-3 mm. in diastolic pressure. Errors were consistent in direction in 11 of the 12 tests. Digit preference diminished as the survey continued (61% terminal 0 first readings, 54% terminal 0 second readings). Results

The defined population was 476 men and 436 women. First readings were obtained from all the men in the practice, and all the women but 2 (both pregnant). Second readings were obtained from 471 men (98%); the other 5 men had left the district. Patients welcomed the principle and practice of pre-

High blood-pressure is

TABLE II-FEMALE ARTERIAL PRESSURES BY AGE

measured

directly (the main effect was to prolong the time of contacts rather than to multiply them) but the rate per patient per year was 4-2 in each of the two survey years, compared with 4-3 in each of the two preceding years. By these crude yardsticks, then, all the work was contained within the previous limits; the fall in consultation-rates that probably occurs in any well-run practice after about five years 15 permits the planned extension of work in new directions, even in South Wales with its exceptionally high mortality, morbidity, and workload. 16 The extra work would have been much reduced had an attached health visitor been available. The readings were made over a wide span of time, with a variable lapse between first and second readings. The median lapse was 18 months, and 88% had a lapse of less than two years. The mean differences between first and second systolic and diastolic pressures for the 17 cases with a time-lapse of more than five years were -5-5 mm. and —70 mm. respectively; so there is no evidence that during the survey blood-pressure rose significantly with age. All those with diastolic pressures at or over 100 mm. were followed up with at least two more readings. Those with three or more readings at or above Pickering’s levels were investigated by examination of the heart and fundi, electrocardiogram (E.C.G.), chest X-ray, urine for protein and TABLE I-MALE ARTERIAL PRESSURES BY AGE:

usually discovered incidentally, and every doctor must have experience of the need for tact and a sense of proportion when this happens; the situation differs little when hypertension is discovered by deliberate screening, provided the doctor is known to the patient, and is prepared to follow up the case and take responsibility for perhaps many years of supervision and treatment. Only one man made a conditional refusal (that he would only take part if he became the sole non-respondent); he had a diastolic pressure of 170 the age of 44 without symptoms. His bloodpressure had never been taken before. Mean systolic and diastolic pressures with standard deviations are shown for male first, second, and mean mm. at

FIRST, SECOND,

AND MEAN OF FIRST AND SECOND READINGS

225 TABLE m—PERSISTENCE THROUGH THREE READINGS OB DIASTOLIC PRESSURES WARRANTING TREATMENT

40 mg. per 100 ml. E.c.c.s and venous blood were men under 40, and 1 over 40, who left the area. 9 of the 26 men and 6 of the 12 women were already under treatment when screening began. All the " new " hypertensives were considered for treatment, after a further period of observation to see if further readings fell below the defined levels; this was so in 2 of the men and the only woman under 40. The response-rates, results, and logistics of making treatment available to the whole group will be reported over

not

obtained from 3

later.

of first+ second readings in table i, and for single readings in women in table 11. They are higher in every age-group than the figures for the Rhondda Fach reported by Miall and Oldham,14 whose population was socially almost identical with mine; their figures may indicate very roughly the difference to be expected between pressures measured by the best epidemiological techniques, and those found by general practitioners in the course of their work. There was no consistent movement between first and second readings of systolic pressures, but diastolic pressures fell in every age-group by a mean 3-4 mm. Table in shows the numbers with diastolic pressures persisting at or above Pickering’s levels, through three readings on separate occasions. 16 of the 26 hypertensive men, and 5 of the 12 hypertensive women, were identified for the first time by screening. Of those already known to be hypertensive, 6 men and 1 woman were identified incidentally to examination for complaints unrelated to their hypertension. The remaining 4 men and 6 women were identified when they presented with symptoms related to hypertension and/or atheroma, at various times between 1958 and 1968. Table iv shows the number in each of these groups with signs of left ventricular hypermm.),18 and mean blood-ureas trophy (RV5+SV1>30

Discussion for Screening hypertension has attracted less detailed discussion than screening for diabetes,

anaemia, cervical

cancer,

glaucoma,

or

phenylke-

This is surprising, since it is common, dangerous, affects an economically important agegroup, is usually symptomless, and is treatable at primary-care level with proven effect on mortality. So far as I know the British literature, the subject has been discussed at length only by Holland,19 who concluded that screening for hypertension could not be justified on present evidence. In fact, hypertension is already diagnosed by screening as a rule, and when it presents with symptoms these are often irreversible. The screening is haphazard and unplanned-by examinations for insurance, before employment, or in general practice or hospital outpatient departments in the course of examination for unrelated complaints. Some doctors may indeed take blood-pressures, and see their patients, so often that all their hypertensive patients are known to them (that is, they are already screening); but despite a special interest in the subject, only half of mine were known to me after six years. Holland uses a three-stage classification of hypertension, without relation to actual levels of pressure:

tonuria.

"

In stage i there are no objective signs of organic in the cardiovascular system ... stage 11 is based

TABLE IV-EVIDENCE OF ORGAN DAMAGE IN DEFINED HYPERTENSIVES

change on

the

226

objective signs of left ventricular hypertrophy ... Detection of subjects with stage 11 essential hypertension is important there is no question that treatment should be given and is already being given, but it is stage i that would be discovered by screening or early diagnosis." ...

He continues:

ANIMAL SOURCES OF COMMON SEROTYPES OF ESCHERICHIA COLI IN THE FOOD OF HOSPITAL PATIENTS POSSIBLE SIGNIFICANCE IN URINARY-TRACT INFECTIONS

"

If it is established that the treatment of raised blood pressure without any of the known symptoms or complications is of value then the implications in terms of cost and At least 5-10 per cent of the resources are considerable. population would be eligible for such treatment." The screening procedure reported here detected a man of 37 with a sustained diastolic pressure of 130 mm. without symptoms or E.c.G. evidence of hypertrophy (stage I on this classification), and another of 44 with a sustained diastolic pressure over 150 mm.; he had an abnormal E.C.G. and a raised blood-urea, but was quite free from symptoms and knew of no reason to consult a doctor. Signs are not symptoms, and it is difficult to see the value of the three-stage classification unless it is qualified by some reference to specific levels of sustained diastolic pressure. After all, such evidence as we have all points to the actual level of blood-pressure as the cause of organ damage and the target of treatment. If we do not screen, we shall miss the opportunity to treat a lethal condition at a favourable stage; and if we do, using reasonable criteria to define hypertension needing treatment, we shall find about 4% of the population between 20 and 64 in this category. Any doctor capable of organising a screening programme should be able to cope with this number, though the work would be sufficient to deter treatment without indication (which is very common at present). The real question is not whether to screen for hypertension, but to define on better evidence and with greater precision the criteria for treatment. Such criteria should refer to average levels of diastolic pressure, and not depend only on evidence of organ damage or the presence of symptoms. This work was supported by an Upjohn travelling fellowship, by the research foundation board of the Royal College of General Practitioners, and by the Welsh Hospital Board who supplied the E.C.G. machine. I am particularly grateful to Prof. W. R. S. Doll for generous help and criticisms: to Prof. A. L. Cochrane, Prof. Donald Reid, Dr. W. E. Miall, and Dr. G. A. Rose; to Dr. A. Adams and the staff of the Neath Hospital laboratory ; and to Dr. R. T. Rouse, of Imperial Chemical Industries, for help with the calculations. REFERENCES 1. Aurell, M., Hood, B. Acta med. scand. 1964, 176, 377. 2. Hamilton, M. Proc. R. Soc. Med. 1966, 59, 1185. 3. Veterans Administration Co-operative Study Group. J. Am. med. Ass. 1967, 202, 1028. 4. Smirk, F. H. N.Z. med. J. 1964, 63, 413. 5. Cope, J. T., Smith, D. H. Br. med. J. 1967, ii, 756. 6. Scott, R., Robinson, P. ibid. 1968, ii, 643. 7. Evans, S. M., Wilkes, E., Dalrymple-Smith, D. J. R. Coll. gen. Practnrs, 1969, 17, 237. 8. Taylor, M. P. ibid. 1970, 19, 146. 9. Hodes, C. Lancet, 1968, i, 1304. 10. Fry, J. Profiles of Disease. London, 1966. 11. Pickering, G. High Blood Pressure. London, 1968. 12. Bechgaard, P., Kopp, H., Nielsen, J. Acta med. scand. 1956, 312,

suppl.

E. MARY COOKE ALWENA L. BREADEN

R. A. SHOOTER S. A. ROUSSEAU

Department of Bacteriology, Hospital, London E.C.1

St. Bartholomew’s

The hospital food, the hospital kitchen, Summary the meat on arrival in the hospital, and and the environment in an abattoir and a poultry-packing station, have been examined for the presence of Escherichia coli. Large numbers of the organism were found in all these situations. We suggest that this constitutes a route by which strains of E. coli from animals reach the human population. The administration of antibiotics to animals may be followed by the establishment of antibiotic-resistant strains of E. coli in the human bowel, with the subsequent appearance of urinary-tract infections which are more difficult to treat. the

meat

Introduction

PREVIOUS work has shown that this hospital’s patients have a changing faecal population of Escherichia coli,l and that the hospital food is the probable source of the new strains that the patients acquired.2 In this paper we describe work that was done to discover how the food became contaminated, and the source of the contaminating strains. Since we knew that E. coli could be isolated from meat and poultry on its arrival in the hospital, we carried out our investigations in an abattoir, in a poultry-packing station, and in the hospital kitchen, where we examined the articles used in the preparation of food and the food itself. Materials and Methods Abattoir and Poultry-packing Station

Cattle, sheep, and pigs were slaughtered in the abattoir. The poultry-packing station had been open for six months: approximately 13,500 chickens were killed and packed daily. Both buildings were well maintained and the standards of hygiene were good.

Hospital Kitchen The hospital kitchen was built in 1907 and consisted of a large open room of approximately 2000 sq. ft. (186 sq. m.), with vegetable preparation, pastry, and washing-up rooms opening from it. Washing-up was done by hand using a detergent. Meat coming to the kitchen first passed through the butcher’s shop, which was on the floor below. Meals for some 500 inpatients were supplied daily, as were some 900 lunches and 400 breakfasts and suppers for the hospital staff. Forty people were employed in the preparation and distribution of food.

175.

13. Hart, J. T. J. R. Coll. gen. Practnrs, 1970, 19, 258. 14. Miall, W. E., Oldham, P. D. Clin. Sci. 1958, 17, 409. 15. Marsh, G. N. Br. med. J. 1968, i, 633. 16. Williams, W. O. Royal College of General Practitioners. Reports from General Practice XII, January, 1970. 17. Rose, G. A. Lancet, 1965, i, 673. 18. Sokolow, M., Lyon, T. Am. Heart J. 1949, 37, 161. 19. Holland, W. W. The Early Diagnosis of Raised Arterial Pressure. London, 1967.

of Meat and Poultry Preliminary work having shown that E. coli contamination of meat was confined to the surface, meat was examined by rubbing a swab over an area of variable size. The swab was cultured on a MacConkey plate. Swabs from the

Examination

exterior and interior of chicken carcasses in the same way, and in addition the giblets

were

examined up and

were cut