293

Though the term " nephritic syndrome " has beenused here as the basic framework upon which to developthe clinical description, in any particular case thealbuminuria, the hypertension, the oedema, or all three,may be absent. The two features which we regard asthe most important, and the most often encountered,are (1) a disproportionate tachycardia, especially if

supported by electrocardiographic evidence of wide-

spread myocardial involvement ; and (2) a persistentmoderate polymorph leucocytosis without any other

adequate explanatory cause. These two features were

emphasised by Lamb (1914).SUMMARY

Attention is drawn to the fact that polyarteritisnodosa only carries a 50% mortality, and that skinnodules and eosinophilia, previously regarded as

pathognomonic, are uncommon.A case is reported in which the clinical manifestations

were observed for seven weeks and the diagnosis wasconfirmed post mortem.The clinical picture may be pleomorphic, but there

is almost always clinical evidence of renal involvement.Two other diagnostic " signposts " are a disproportionatetachycardia and other evidence of myocardial involve-ment, and a persistent moderate polymorph leucocytosis.Our thanks are due to Sir Adolphe Abrahams for permission

to publish the case and for much help and advice, and Mr.E. F. King for opinion on the fundal changes.

REFERENCES

Curtis, A. C., Coffey, R. M. (1934) Ann. intern. Med. 7, 1345.Harris, A. W., Lynch, G. W., O’Hare, J. P. (1939) Arch. intern. Med.

63, 1163.Lamb, A. R. (1914) Ibid, 14, 481.Miller, H. G., Daley, R. (1946) Quart. J. Med. 15, 255.Strong, G. F. (1928) Canad. med. Ass. J. 19, 534.

MINIMAL REQUIREMENTS FOR MASSRADIOGRAPHY

F. C. S. BRADBURYM.D. Belf., B.Hy., D.P.H.

CENTRAL CONSULTANT TUBERCULOSIS OFFICER, LANCASHIRECOUNTY COUNCIL

DOUBT has arisen about the value of mass radiographyin that the return may not be commensurate with the

expense, as foreseen from the beginning by manyin the tuberculosis service. One obvious method of

preventing this result is to use mass radiography solelyfor selected groups in whom tuberculosis is expected tobe more than ordinarily prevalent. This is the method

usually followed at present. A drawback to the exclusiveuse of this method is that mass radiography wouldcome to be associated with susceptibility to tuberculosis,and to be singled out for mass radiography would betantamount to being labelled a tuberculosis suspect.This seriously limits the use of mass radiography.A better method, which could include the foregoing,

would be to make sure that by adequate propaganda4 high proportion of the examinees in any group to besurveyed could be expected to attend for examination.There are two reasons behind this statement. First,the common-sense argument that there must be someminimal effectiveness of mass radiography below whichthe procedure is not worth while. Some would perhapsplace this minimum at a single person and say that ifa survey discovers one tuberculous person it has beenworth while ; but it is not difficult to reject this extremeview. Secondly, it may be expected that if two-thirdsof a large group of people agree to participate in a mass-radiography survey and a third decline, the reasonswhich caused the third to decline will lead to the existenceof more cases of tuberculosis per 1000 in the abstaininggroup than in the two-thirds who participate. In otherwords, the greater the proportion of persons examinedin any group, the greater will be the percentage incidence

INCIDENCE OF TUBERCULOSIS IN RELATION TO PERCENTAGE

OF PERSONS EXAMINED

of tuberculosis discovered, because it will more andmore approximate to the true percentage incidence inthe whole group.That this is no mere speculation is shown by the

figures relating to the last five surveys carried out bythe Lancashire county council no. 1 mass radiographyunit (see table). ,

The question now arises whether any lower limit canbe fixed to the effectiveness of mass radiography, belowwhich its use cannot reasonably be justified. Clearlysuch a limit must be arrived at from practical con-sîderations. I suggest that, to be worth while from thestandpoints of cost, man-power, and effective controlof infection, a mass-radiography survey should discovermore tuberculosis than it leaves undiscovered. To placethe limit any lower than this would incur the risk ofactual harm being done by a mass-radiography surveyowing to the false sense of security which might reasonablyattach to a group which had been so inadequatelysurveyed that the greater part of its initial content oftuberculosis still remained undiscovered. -

If it is accepted that the limit of effectiveness of asurvey is the discovery of at least half the tuberculosisin any group, it can be shown that the proportion ofpersons who must be examined to satisfy this requirementis about 70%. This figure is derived from the foregoingtable in the following manner : , ,

It is noted from the table that the variation in the amountof tuberculosis detected by mass radiography is almost

directly proportional to the percentage response. This’meansthat if 100% response gave 10 tuberculous persons per 1000examined, a 40% response would give 4 tuberculous personsper 1000 examined, and the degree of adequacy with which apartial examination represents the percentage incidence, oftuberculosis in the entire group will vary with the squareof the percentage examined. Hence if 100% examinationgives all the detectable tuberculosis, 70% response will give(70)2

or 49% of the total tuberculosis in the entire group-100i.e., 70% of the total because only 70% ,are examined ; andthis figure is again reduced to 70% of itself because theexpected incidence of tuberculosis is only 70% of the incidencein a representative sample.

It is possible to obtain a similar result by calculationfrom the known incidence of tuberculosis in the generalpopulation, without the information given by the pre-ceding table, but the calculation is too complicated forgeneral use.

In view of the loss of time associated with the dis-mantling, transportation, re-erection, and testing of theapparatus each time it is moved, it is scarcely practicableto arrange a survey for less than about 4000 persons,except as part of a larger survey.

SUMMARY ’

There is a lower limit to the efficiency of mass

radiography, below which it becomes uneconomical. Itis suggested that a practical measure of this lowerlimit would be the point where mass radiography leavesundiscovered more tuberculosis than it discovers.On this basis it is shown that not less than 70% of

any group to be surveyed should actually be examined.