Intravenous iron.
Journal: BMJ (1965)

the other hand, if the curve of the frequency distribution does not assume this form but has two or more peaks, then one or more dominant factors are at work.In theory the problem is simple.Thereafter it resolves itself into the acquisition of enough accurate measurements of blood- pressure in a sample of people representative of the whole population.Pickering's review of the evidence suggests strongly that the level of blood-pressure is " normally " distributed-that is, no one factor is a dominant cause.Any distortions noted are considered to.be due to the preference for certain digits that people who must make many measurements often show.In fact, the evidence for multiple causation seems to be as good for blood-pressure as it does for stature.Platt claims that data on the blood-pressure of siblings of patients with essential hypertension, when displayed as a frequency distribution, suggest that essential hypertension is due to an inherited dominant gene.This conclusion has been criticized on the argument that the bimodality of the curve is due to the effect of digit preference by the observers.More recently Platt has studied a group of relatives of hypertensive patients and claims that the shape of the distribution curves of their blood-pressures suggests there are three groups distinguished by mode of inheritance of factors causing hyper- tension.These conclusions have been criticized as being based on insufficiently large numbers.So far the weight of evidence seems to favour the multi- factorial hypothesis of Pickering, but students of clinical science should not accept the opinion of reviewers: they should study the data for themselves.Fortunately this is possible, because the principal publications in this field include the " raw " numerical data, enabling the reader to make his own statistical analysis and draw his own conclusions.This is as it should be and does credit to the editorial policy of the journals concerned, particularly Clinical Science.Scientific reports should describe the methods of observation and experiment and give the results in such detail as to enable others to repeat the work or to fit the data into some other hypothesis.Numerical data fully reported are eternal, while discussion and debate are contemporary and ephemeral.It must not be thought that this controversy is a purely academic affair of little concern to the practising clinician, for the opposing hypotheses differ fundamentally on the causation of essential hypertension.The view that one or more dominant inherited factors are creating a distinct " abnormal " population of hypertensives implies the need to concentrate on genetic studies and on possible ways of controlling the effects of such inheritance.The multifactorial hypothesis, on the other hand, offers wide scope for the detection of the many environmental factors promoting the higher values of blood-pressure.Pickering summarizes the results of the statistical analysis by W. E. Miall and P. D. Oldham' of their blood-pressure readings in a large sample of first-degree relatives living in the Rhondda Fach and the Vale of Glamorgan.These point strongly to the inheritance of blood-pressure quantitatively as a graded characteristic, and the analysis suggests that about two-thirds of the variance is due to non-familial environ- mental factors.Some of these factors are known already- such as obesity, physical work, and family size.The recog- nition of others is the opportunity of the clinician, particularly the family doctor, who is prepared to measure blood-pressure, take weights, keep records, keep an open mind, and use his wits.