Document RwM5DXxMnq2bo4kXZvDo70wn

February 8* 1938 Dr, Honnath Blackfan Children*s Hospital 300 Longwood Avenue Bos t on * Ifas 3, Dear. Doctor? Blackfan*- In accordance with the request in your letter of February 2nd* I am sending you two papers from, the laboratory* one of which gives the details of our dithlzone method, and the other gives a rath dr derailed eonparison of the difchizone and the spec** trographie methods, You will note from the latter paper that the results obtained from the two methods are sub stantially the same* la fact the accuracy of the method of analysis is considerably more than the accuracy of our phys iol ogi cal in t erpreta fci on of the resul ts , This * I believe* will serve to answer your question as to whether the use of the dithisone method has modified my opinion as to the normal blood levels* The figures which I gave' you In my letter of last June are* therefore* substantially correct* I may say that in some recent data on two experi mental subjects followed over a period of months under laboratory conditions* the mean result in the blood was 0*032 mgs* per 100 grams' of blood* with variations extending from:: 0!01'!'t.;0:ot*' This* I believe*: fairly ..represents the normal range of values. Perhaps I should poio.t out to you* however* that it is easier to recognise abnormal findings in the urine than it is in the blood* For example* we have recently studied several groups of workmen in lead trades in which the lead exposure was relatively small# These groups could readily be differentiated from each other on the basis of the urinary findings* but one did not find a significant statistical difference in the groups on the basis of their mean blood levels. To be still more specific* an unexposad group had a mean blood lead level of 0*038 mgs* por 100 grams of blood and a urinary level of about 00i| mgs. per liter. A very' slightly exposed group had a corresponding blood lead level of O.Ol^ and a corresponding urinary level of 0.08. The differences in the urinary values were statistically significant while the differences between the blood levels were not statistically significant* and therefore provided no basis for differentiation. As a matter of fact, we have found uniformly that where urine samples can be collected in such a way as to avoid any possible contamination, they ,9 .** are more useful for diagnostic purposes than any other type of biologic material* I have always felt it necessary to be cautious in the acceptance of the diagnostic significance of any analytical results of a borderline type* Thus, if the blood findings are in excess of a tenth of a milligram per ICO grams of blood, one can be fairly sure of significant exposure* By the same token, if urinary results are corres pondingly high, the Interpretation is not difficult. My only point is that the urinary results in a given case are more likely to be definitely abnormal than are the blood findings I am not quite certain as to the physiologic interpretation of this fact, but that it is a fact is without doubt, I personally like to have both blood samples and urine samples for analysis In most eases, and in some instances, especially those with recent exposure, I like to have fecal samples also* The latter are, of course, the least useful in most'cases since it is very difficult to interpret the results of a single fecal analysis on account of the extreme variability of the lead content of the food material* In the case of children, however, on several occasions a diagnosis has been made possible by the discovery of paint-cover?d fragments of wooden objects In the stool. Incidentally, before concluding, I should point out that in our experience, there is very little difference in the rate of lead excretion of children as compared to adults, whether under normal conditions or under conditions'of load exposure* I am not prepared to say that this la always the ease, but so far we are not justified in differentiating children frero. adults with respect to rate of lead excretion* Sincerely yours, , RAKjis Robert' "a * KehoM.D. KE 0020098