VITAL CAPACITY IN HEART DISEASE
Authors: H. W. Jones
Journal: BMJ (1928)

5 I r-.._.DCAL JCREAL would be perfectly satisfactory.But in actual practice the larger the " samlple " the less probable is it thlat the con- (litionis wvill be fulfilled, and the possibility of controlling a saml)le of the order of 10 per cent. of the whole annual.. births is virtually all impossibility.Take a less ambitious scheme, and suppose that in some town. of moderate size, a town of some sixty or seventy thousand inhabitants, with all annual quota of, say, 1,000 births, the children could be treated randomly-for example, every second child whose birth was registered from January 1st in some year to be treated.We should expect on the average less than one registered death from tuberculosis in the control 500, and no strong presumption of advantage would be raised by a nil return from the treated series, taking only a year's experience.Evidently it was a sound instinct to seek for a decision amongst the class of material where a higher rate of mor- tality w'as to be expected.That is the significance of Kjer-Petersen and Ostenfeld's work.What can we conclude from their investigation as to the probable range of mor- tality in the first year of life of in-cantacts?We can, of course, at once dismiss the preposterous suggestions of rates of mortality of the order of 25 per cent., even from all causcs.Had such a rate really prevailed in the population sampled by Rjer-Petersen and Ostenfeld, their --" expectation w-ould lhave been 61 deaths with a standard deviation of 6.77.Actually they observed 19, and thle odds against such a.deviation as 42 are of-the-order of a thousand millions to.one.If, however, one might l)ostulate a rate of mor- tality from tuberculosis in the first year of life even of the order of 5 to 10 l)ei cent., the comparison of samlles of ordei 500 would not be waste of time.We should expect in our control 500 from 25 to 50 (leatlis, and if the treated sample returned,-say, only some 15 to 30 or fewer deaths.a case would have been miade out whichb wfAould be raathlerl strong.Whether it would be l)ractically 1)fsihle to uise this method, here or in Anerica, it is hai'd to sav.The number of instances of births in families with one or lmlore cases of open tuberculosis which come to the notice of the public health authorities within any one area aend within a limited period of time is small, and the difficulty of strict random sampling is great.We are concerned, not with guinea-pigs, but with human beings, and it is not casy to induce those who have the medical charge of human beings to administer to any of themi a treatment which they regarld as worthless, or to abstain from administering to any of them a treatment which they regard as Calualle.None of us can dramatize this conflict with the art of Mr. Sinclair Lewis in Martin A rmoi(l-ith,, but all of us have, to a greater or less degree, parti ipated in it.1 do not expect that the value of B.C.G. wzill be determined on t-hlese lines.Like most methods of tie stment, its usew or neglect will be determined by psychological considlerations.But to the still small, but incriasing, nuumoer of medlical men who attach importance to statistical accuracy it is of some m.oment that methodological eriors having the sanliction of the nanae of a distiigouished investigator slmould at once be pointed out.T1hat is my season for writing this a'rti(le.