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Special Articles

THE PATTERN OF MASS RADIOGRAPHY *E. G. W. HOFFSTAEDT

M.D. Berlin

ASSISTANT CHEST PHYSICIAN, HOLLYWOOD HALL SANATORIUM,WOLSINGHAM, DURHAM

. THE following figures, based on the work done bymass-radiography units in Region 1 during 1949, givesome idea of the cost of case-finding by this method.Four units were in action, three of them completelymobile and independent, and they took betweenthem 97,250 miniature films during the year. Whenall the expenses of running the units are taken intoaccount the average cost per miniature film works outat 4s. 6d. Cases sent for further investigation, as a resultof suspiciQus findings in the miniature film, numbered6247, or 6-4% of the total examined. Large filmstaken of these cases worked out at a cost of 1:3 8s. 10d.each.The incidence-rate of pulmonary tuberculosis dis-

covered by mass radiography seldom exceeds 2%.Using the figure of 4s. 6d. as the cost of a miniature filmit is possible to calculate the cost of -discovery of a singleactive case of pulmonary tuberculosis at differentincidence-rates, as follows

Incidence-rate Cost per case discovered% k s.

0.35 .......... 64 100-4 .......... 56 50.5 .......... 45 01-0 .......... 22 101.5 .......... 14 172-0 .......... 11 5

These would be the costs in an average survey ; but itis possible to find extreme examples where the cost

- per case discovered is much higher, as in thefollowing :Over a period of 21/2 months an area with an adult popula-

tion of 53,790 was surveyed. The total number who volun-teered for examination was 2315, or 0’04% of the population.Of these, 34 (1’5% of the number examined) were referred tothe clinic for further examination, and 9 cases of pulmonarytuberculosis were found among them ; but 7 of these were

*Based on a communication to the Tuberculosis Associationon Nov. 24.

TABLE I-COST ANALYSIS OF CASES EXAMINED BY TJNIT " N "

IN 1949

Cost per case discovered : 54 7s.

known already to the clinic. Only 4 were active cases, and 2of these were already on the register ; so the survey revealed2 new active cases which had been unknown before. The costof the survey was 1264, giving a cost per single examinationof 10s. 6c.. ; the cost per patient referred to the clinic was37, and the cost per newly discovered case of activetuberculosis 632.

’

Table i compares the discovery-rates (and their cost)in routine surveys, in factories and elsewhere, with thediscovery-rates in surveys where the cases were selectedas suspicious by doctors or chest clinics. It will be seenthat the cost per case discovered is f:8 4s. lOd. where

suspected cases only are examined, as against n09when unselected populations are surveyed. In this

particular survey the average cost per miniature filmworked out at 3s. lOd.

For comparison, the figures from another unit (unit " D ")may be considered. In this unit the overhead expenses weresomewhat higher than those of unit " N," the cost per minia-ture film in 1949 working out at 4s. 9d. Unit " D " had anaverage discovery-rate for all cases of 0’67%, the cost per

TABLE II-ANALYSIS OF RESULTS WITH DIFFERENT GROUPS OF

PEOPLE EXAMINED IN NEWCASTLE IN 1949 (UNIT " N ")

active case discovered being 35 12s. At sessions open to the

general public the discovery-rate was 1%, and the cost peractive case found B23 15s.

It will be seen from table I that the discovery-rate, asmight be expected, was lower in routine surveys andopen sessions than in selected cases sent by doctors orclinics. Table II, which gives the discovery-rates ofunit " N" with four different groups, emphasises thispoint. When large numbers of supposedly healthy peopleare examined as in routine surveys) the discovery-rateis low. At open sessions for the public it is somewhathigher because those who are anxious about their healthare more likely to attend than others, and the group istherefore self-selected. Among people referred by doctorsand clinics, the discovery-rate is naturally still higher.Table II shows not only that the discovery-rate washigher in groups 3 and 4 (the selected groups) but thata higher proportion of those kept under observation orreferred to the clinic from these groups turned out tohave tuberculosis than was the case with groups 1 and 2.

SOME FACTORS AFFECTING RESPONSE

Table III shows one of the weaknesses of unselectedsurveys : in five large factories the discovery-rate fellas the response fell. (Only one factory (factory A) liesoutside this pattern ; possibly there was contact infee-tion, or some other special cause, to account for thisdiscrepancy.) Bradbury 1 made a similar observation in1948.

Response to an offer of mass-radiography examinationvaries, among other things, with the way the offer ismade. If candidates are asked to attend if they wish(to contract in) the response is always poorer than ifthey are asked to say they will not attend (to contractout). Thus Sheffield unit found that with the contracting-

1. Bradbury, F. C. S. Lancet, 1948, ii, 293.

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in system the response was 52-78%, while with thecontracting-out system it was 74-84%. In other words,people do not care to say they are unwilling. On theother hand, even the contracting-out system may geta poor response if other factors interfere ; thus of allthe pregnant women attending antenatal clinics inNewcastle who were booked for radiography (contracting-out system) only 60% attended. They will bring theirchildren to the welfare clinics, because they get goodadvice and vitamin supplements ; but they are lessready to interrupt their daily chores to go and be investi-gated for a disease they have no reason to think theyhave acquired.

LIMITATIONS OF MASS RADIOGRAPHY

The contribution of mass radiography to case-discoveryis on the whole modest. Of all the new cases on theregister of a big urban chest clinic in 1949, only 18-5%had been discovered by this method ; and in a randomsample of the population in a sanatorium, only 33 (20%)of 162 men had been found by mass radiography. It isworth noting that of these 33, no less than 14-nearlyhalf-had been picked out by mass radiography shortlyafter joining the Forces. In a random sample of 145patients in the same sanatorium in 1947, the proportionpicked up by mass radiography was only 11%. Inanother sanatorium, in 1949, 15 out of 104 women, and11- out of 70 men had been found in this way (15% inboth cases) ; but again nearly half of the men so

discovered had been picked up in the Forces.In any case mass radiography of the total population

on a voluntary basis cannot even be attempted. Theunits and personnel at our disposal cannot deal withmore than a small fraction of the adult population. Oneunit can manage 25,000-30,000 miniature films a year.In Region 1, with a population of over 2,700,000, five unitsare now operating. Average samples from a rural districtand a large town indicate that 72-5% of the people inthe region are aged 15 or more, and the adult populationcan therefore be reckoned as 2,110,000. The five units

TABLE III-RESULTS OF SURVEYS CARRIED OUT ON THE

PREMISES OF FIVE LARGE FACTORIES

’Discovery-rates reckoned as 25 % of the cases referred to the clinicor kept under observation (of table i).

can deal in a year with only 150,000 people, or 7%, ofthe adult population of the region.

SUGGESTED USE OF MASS RADIOGRAPHY ’

In this region it is intended that routine surveys shouldbe made in hazardous industries, especially dusty occu-pations like mining, sand-blasting, and steel-dressing ;in industries and factories known to have an unusuallyhigh incidence of tuberculosis, such as tobacco and

clothing factories, especially those employing youngwomen ; and in any factory or workshop in which anunusual proportion of employees are known to havedeveloped tuberculosis.

In addition, it is proposed that there shall be quarterlysessions at every main centre of population, at which thefollowing groups would be regularly examined :

1. All school-leavers, and any other school-child referredby the school medical officer or the family doctor.

2. Teachers, school kitchen-staff, and all others in regularcontact with children (e.g., kindergarten and nurseryschool staff, and staff of welfare clinics).

3. All young people of both sexes about to enter the Forces.(This could be arranged in collaboration with theMinistry of Labour and National Service.)

4. Prospective candidates for employment, at the requestof their firm or employing body (e.g., the Civil Service).

5. Women attending antenatal clinics.6. Chronic sick ; and all suspects, with symptoms, sent by

family doctors, factory doctors, or medical officers ofhealth.

7. Patients referred from chest clinics.

8. Contacts, for regular examination and follow-up. (Thiswould be arranged on behalf of, and in collaborationwith, the chest clinics.)

9. Volunteers from the general population who wish to beexamined.

I believe that by keeping to these groups we could usemass radiography much more effectively and econo-mically than we are doing at present.My thanks are due to Dr. F. L. Wollaston, Dr. W. H.

Dickinson, and the organising secretaries of the Durham andNewcastle Unit, and to the staff of the Newcastle RegionalHospital Board, who kindly supplied the material on whichthis paper is base.

MINIATURE RADIOGRAPHY WITH

4 × 5 INCH CUT FILM

OWEN CLARKEM.A., M.D. Camb.

SENIOR MEDICAL REGISTRAR, PAPWORTH SANATORIUM

MINIATURE radiography had been under considerationfor many years before the late war. D’Abreu (1945)has described his own earlier work in France and Brazil,and Bentley and Leitner (1940) were also experimentingin this country ; but it was the war which provided theurgent spur to more rapid development of techniques.Trail (1942), Trail et al. (1944), and Brooks (1944a)were the leaders of progress in the British Services, andwhen the U.S.A. came into the war there was a widedemand in America for routine chest radiography beforeenlistment. The purposes of miniature radiography inboth countries were essentially the same-to avoid theintake of tuberculous people into the Services, and byroutine examination of Service personnel to detectcases of pulmonary tuberculosis as early as possible.

After the war, development was directed towardsthe survey of civilian populations, and once again theemphasis was on quantity and, on speed of operation ;individualii y was not considered important. In a

report to the Medical Research Council, Clark et aL(1945) considered the relative merits of 35 mm. film andthe 4 x 5 in. stereoscopic films which had provedso popular in the U.S.A., and they decided in favourof -the smaller film. It was generally agreed’that inskilled hands the technical results were equally good,and for civilian mass radiography the 35 mm. film" had the added advantages of mobility of apparatus,larger numbers of examinations in a shorter time, andmuch more rapid processing and interpretation." (loc.sit. p. 2.) There is also the advantage of compactnessin storage with 35 mm.

These factors are important for mass miniature radio-graphy ; quite different considerations arise whenminiature radiography is to be a part of clinical andpreventive medicine, divorced from the urgency androutine of a mass survey. In Britain only 35 mm.roll film has so far been obtainable, and all attentionhas been focused on mass surveys, but the technical

efficiency has developed to such a high standard thatwe should now consider the use of miniature photo-