ffune i956 E P I D E M I O L O G Y AND MEDICAL E R R O R 9 I I

and the memorandum was published with a covering letter o n October 12th. The year before William Budd wrote his memorandum Villemin had presented to the French Academy of Medicine his experimental proof that tuberculosis was indeed an in- fectious disease, and that the agent producing it was present in the pus from tubercu- lous cavities. 5

Speculation on the value of William Budd's contribution to the knowledge of tuberculosis would be interesting. Although he left m a n y unpublished manuscripts When he died in i88o the memorandum with the story of the walk on Observatory hill in i856 appears to be his only published work on tuberculosis. I t is a fitting tribute that in i956 the British Tuberculosis Association should have been invited to hold its Annual Meeting at Bristol and that the opening discussion should be on epidemiology. x Budd, W., Lancet, 1867, 2, 45 x. 2 Bricheteau, I. Tralt6 sur les Maladies Chroniques qui ont leur Si~ge dans les Organs de l'Appaxeil

Resplratolre. Paris, x851. Cotton, R. P. The Nature, Symptoms and Treatment of Consumption. London, 185.~.

4 Clark, J. A Treatise on Pulmonary Consumption, London, x835. s Villemin, J. A., Bull. Acad. 3Ied., Paris, x865 -66, 21, 211.

Epidemiology and Medical Error A recently published monograph on tuberculosis in the United States Army during the Second "~Vorld "~Var illustrates once again what an excellent stimulant to medical research war can be. l The authors have compared the induction and discharge chest radiographs of about 3,000 randomly selected US ex-servicemen discharged for tuberculosis, and 3,000 ex-servicemen, also randomly selected, who were not dis- charged for tuberculosis. The results fall into two main groups - epidemiological and radiological.

Epidemiologically the most striking.feature was the importance of racial and constitutional factors. For instance, the rate of appearance of tuberculous lesions in non-whltes was significantly higher than that amongst whites under comparable environmental conditions. Amongst the whites, tall thin men developed tuberculosis more frequently than men of other physical types; and the possibility o f a n y confusion between cause and effect was excluded. The highest attack rate was found at ages 19 to 22. This confirms the studies in this country that have shown the highest attack rate for both men and women to be in the i5-24 age group, and indicates that the present higher prevalence of tuberculosis in elderly maIes is due to the breakdown of old lesions acquired much earlier in life. I t is also interesting that foreign service by itself did not affect the attack rate of tuberculosis, ahhough certain theatres of war were associated with increased breakdown rate: The attack rate was, however, signifi- cantly higher amongst prisoners of war.

Radiologically the most important finding was the e r r o r discovered when the induction films were re-read independently by two radiologists. The extent of the disagreement between these two was analysed in considerable detail and found to be substanti&l. Further anaIysis showed that approximately half of the men discharged for tuberculosis had the disease at the time they were accepted for the Armed Services in a form in which it could have been diagnosed radiographically. The authors themselves comment: 'Their lesions were overlooked in the induction examination for reasons not always evident in the films themselves.' They conclude that the results of dual reading of chest radiographs at induction stations are much more reliable than diagnoses from single readings, and that: ' i f the induction films had each been read by two different radiologists, undoubtedly many more of the men who were tubercu- lous at entry could have been excluded from the Services.' The extent of the disagree- ment between radiologists in interpreting chest radiographs has, of course, been known for many years. Since Birkelo and his colleagues first described it/° there have been

~ I 2 T U B E R C L E June 1956

several papers from many countries confirming their findings. I t is therefore surprising that the Report of the Medical Research Council's Sub-Committee on Mass Radiography 3 - the official British view on this subject - does not even consider such medical error worth mentioning. 1Long, E. R., and Jablon, S. Tuberculosis in the Army of the United States. An Epidemloloeical Study with an

Evaluation of X-Ray Screening. Veterans Administration Monograph, Washington, I (55. 2Birkelo, C. C., Chamberlain, W. E., Phelps, P., Schools, P. E., Zacks, D., and Yerushalmy, J. J. Am.

reed. Ass., x947,133, 359- 3MedicaI Research Council. Committee for Research on Social and Environmental Health. Sub-

Committee on Mass Miniature Radiography. Report. M.R.C, 531687. H.M.S.O., London, 1953.

Tuberculosis and Leprosy Tuberculosis and leprosy are related diseases. Some of the differences between them are obviousand well known. But others are more cryptic; and in this issue Brieger and Glauert compare the electron-microscopic appearances of leprosy and tubercle bacilli. The emphasize that the dissimilarities they observed may not be species differences; for tubercle bacilli grown on culture media were compared with leprosy bacilli in the tissues. The leprosy bacillus has not yet been induced to multiply outside the human body, either in artificial media or in laboratory animals.

Interest in the relationship between the t~vo diseases has been increased by the observations that skin sensitivity to lepromin can be induced by injection of BCG vaccine 1,2,3,4,5 and that lepromin and tuberculin sensitivities are correlated 1,0, v. The relationship is not a simple one. Kuper , for instance, found a positive correlation between the two reactions in patients with tuberculosis but not in those with leprosy or in healthy persons s. Tuberculous patients also showed a greater sensitivity to lepromin than healthy subjects; but some with lepromatous leprosy and slight lepromin sensitivity had very large tuberculin reactions. Accurate investigation of the lepromin reaction is hampered by there being no standard preparat ion of the antigen. Even with the more refined bacillary suspension produced by the Dharmendra method different batches are likely to vary; and at present there is no convenient way . o f comparing their potencies or referring them to that of an accepted standard lepromm. The Research Commit tee of the British Tuberculosis Association is at present studying some of these problems.

The production of lepromin sensitivity by BCG vaccination has, of course, led to the hope that some protection against leprosy might be produced by it. The Expert Committee on Leprosy of the World Heal th Organisation recommended in I95 3 that controlled trials should be carried out before: BCG vaccination could be officially recommendedL Such trials would be difficult to'organize. One has been started in the Loyalty Islands, but, as we have already suggested, 1° it seems unlikely that it will succeed in producing convincing evidence. The present evidence is certainly in- sufficient to justify using BCG for this purpose alone. But its use in countries where leprosy exists need not be justified. For there is adequate evidence of its value in helping to control tuberculosis. There is, indeed, a wide field For further research into the relationship between the two diseases.

Fernandez, J. M. M., Int. 07. Leprosy, x943, I t , 15. Fernandez, J. M. M., Int. J . Leprosy, x951 , 19,474.

a de Souza Campos, N., Int. J . Leprosy, I953, 21,3o7. Kocsard, E., Sagher, F., J . invest. Derm., I953, 21,69.

s Lowe, J., McNulW, F. Int. J . Leprosy, 1953, 21, x 73. ' Chaussinand, R., Int. J . Leprosy, 195o, 18, 44 x.

Lowe, J., McNulW, F., Brit. reed. j . , x953, 2,579- a Kuper, S. W. A., Lancet, x955, 1, 996. 0 Expert Committee on Leprosy, First Report 0953), World Health Org. techn. Rep. Ser., No. 7 L

~a Tubercle, Lond., x955, 37, 57"