Document Dd0BXopXYkZjoqvro1Ban9ojn

3um 15, im Dr*Kenneth D. Blackfan Harvard Medical School Children*s Hospital 300 Longwood Avenue Boston* Maas* Bear Doctor Blackfan1 I have at present a considerable mass of data which have been accumulating over a period of a year or more* and which I am now ready to work up* When I have completed the study of these data* I shall be able to answer the question In your letter of June 7th more accurately than I can do offhand* As to the lead concentrations In the blood of normal persons, and In persons exposed to lead* X am surfe X shall be able to give you very satis* factory figures* X am not quite so oertain In the ease of the spinal fluid for we have not studied enough either normals or exposed to be quite sure of the range of varia bility. f The blood levels of normal persona range from *01 to *05 milligrams per 100 grsas of blood* The mean is somewhere between *02 and *025* (Some time ago we published figures slightly higher than these* but since we have been studying samples obtained only by ourselves and analysed in a laboratory which is free of outside atmospheric air* we have found the figures to be slightly lower.) We have a large enough series of results here that any slight errors In analysis cancel each other* so that there can be no question as to the accuracy of these results* During the past 6 months* we have been doing analyses on blood by two methods operating in parallel* the one our Speetrogr&phle Method as described by Cholak*and the other a modification of the Dithlzone Method as originally described by Fischer and Leopold!, We have seen lead in the blood In various types of plumbism In ooneentratlons extending from slightly in excess of a milligram per 100 grams of blood down to one tenth of a milligram per 100 grama d b blood* In general* two factors appear to determine the- if height of the lead concentration} one* the severity of exposure} and two* the time Interval between the oessatlon n ,, , ,, u4 4o / the severity of the symptoms correlate with the height of the lead concentration, hut this Is not aIsays true* 1 think It Is quite safe to say that the presence of one tenth of a milligram of lead per 100 grams of blood la Indicative of a recent significant exposure to lead* and although symptoms may not be present at this concentration, the existence of symptoms resembling those of plumblsm may be adequately explained* I should be inclined* at present* to regard values under one tenth of a milligram of blood as slgnlfloant only If repeated observations confirm this as the basic level of lead concentration rather than a chance high value, The lead values in the spinal fluid are much lower. From our present data* which are Incomplete* I am disposed to regard values In excess of *01 milligrams per 100 cc of spinal fluid as doubtfully significant! values in excess of *02 milligrams per 100 co of spinal fluid as almost certainly significantj and values above ,0? as definitely Indicative of recent significant lead exposure* X believe when we have sifted the thing as carefully In the case of spinalifluid as we have In the case of blood* we shall probably find the nonsal , values to range between *001 and *01 milligrams per 100 cc* In acute lead coses* we have found values as high as *1 ' milligrams per 100 cc* I believe* without referring at x this time to, my records* that this occurred in only one case in which the diagnosis was at no time a matter of conjecture* This will require confirmation through observations on similar oases* since you will realise* X am sure* that there are numerous opportunities for slight contamlna tion* particularly at the bedside* A a matter of fact* we stake it a point at present not to make analyses of spinal fluid* or of blood either* unless the samples are collected by means of our own needles* Into our own containers* and by a technique which we describe In detail* The use of the ordinary hospital spinal fluid: needle la almost certain to result in contamina tion since the construetion of the needle is such that the fluid may come la oontaet with leadwbearing material* X trust this will give you the Information you require* and X shall be pleased to give you any additional Inf omatlon a a a refinement of this vhen I have completed the study of our data. Cordially yours* RAK {Is Robert "A, kekoe*' M.D*