Document b5g91pZQrkdpDJd1oNoE0eLd3

November128 , 1951 D r . A . G . Cerchione Medicai Exarainer The Pennsylvania Hailroad 9t.h Avenne and 12th Street Al coor.a, Pennsylvania Usar coctor Cerchione : rector Princi handed me your letter of November 25 concerning our efforts to check the results of your (and other) analyses of blood and urine. Since the results relating to lead go through my hands eventually,! am pleased to comment on the results you. forwarded and to reply to your question. With reference to the latter let me say that we shall be lad to have you submit sample of blood for our check. We should prefer to supply the equipment for collecting the samples, since by this means ve can probably reduce the risks of the contamination of samples. We have checked with a number of laboratories* In this manner and we shall continue to help out when we can. Let me know what you want, and we shall forward the equipment. My comments on the tabulated analytical results may be open to certain criticisms, but I shall point out what my experience leads me to believe concerning them. Starting with our own, you will note that our results disagree with each other in two of the four sets of parallel findings. The disagreement is significant, percentagewise, in both instances. Thus it is apparent that there is an appreciable intrinsic error in the procedures. The error of the spectrograpbic analysis is greater, as a rule, than that of the aithizone method. That is, the reproducibility of serial results is lower. Accordingly if there is much discrepancy, we would tend to choose the result of the dithizone procedure as the better. In general, however, if the discrepancy is not great, we would take the average of ths two results as the "best figure. In general our results tend to be lower than those of mc3t good laboratories, for the reason that we have a smaller blank value (a blank includes the minute contamination of reagents, glassware, and laboratory atmosphere, which we control with minute care), than most laboratories would find possible to achieve. In general, also cur parallel results will vary less among themselves than they will in comparison with those of other laboratories, because of our greater experience and our better facilities for this type of work. In general also, the dithizone method is better (more uniform) tbah the spectrographic, while the latter is better than the polarographic. m 0020309 mo7Qs Dr.- A. G. Cerchione - (2) - November 28, 1951 You can look at the tabulated results from this viewpoint and judge them as well as I can. I would say that your results ? R. R. which agree with our average (or preferred.) result in only one instance, are somevliat unduly variable, in that they tend to be high but noc uniformly so. The Brake Shoe results compare favorably with ours in two instances, but are much too htr'.h in two otners. (My impression from their published data and from my jotowledge of some of their unpublished results, is that they -end to run high.) No matter how you look at these results, however, you are bound to conclude that there is an appreciable po;',sroiirty oi significant error in the use of the best of methods and laboratories, and that some duplication of the results is desiranie. That is why we carry out parallel analyses on the blood In the matter of the results on the urine,there are much greater possibilities for errors in the results and in their interpretation, not in the analytical procedures, but in the likelihood of contamina tion. of the camples in their collection and in widu variations in the rat-os of excretion of lead under varying physiological conditions There ape certain advantages in the analysis of the urine, but we prefer to analyse both blood and urine. In 'sampling the urine, especially in medico-legal cases,we prefer to avoid samples of large volume, which can be collected satisfac torily Only -under very close supervision, and to adhere to a spot sample voided directly into the appropriate container (a chemically clean bpttle) in the presence of the examiner. In illustration of the advisability of such procedure, I call attention to your two series of results on the same persons: - J . L. Benton apparently excreted lead at the rate of 0+48 mg. per liter on 11-14-50 and only 0.04 mg, per liter on 11-24-50* This is not an impossible variation, but a very unlikely one. It is likely that the first sample was contaminated. In any case the interpretation fir such results Is quite Impossible, and we would have to make other analyses if we were, to depend on the results obtained on samples of urine. Thus the inclusion of duplicate samples of blood in the diagnostic procedure will clear up any such question. You may ask 'Vhy analyse urines at all, if this is true?" That is a good question. The answer lies in the fact that when the concentration of lead in the blood is at or a little below the threshold value (around 0 .0 8 mg. per 100 grams), the urinary lead concentration is an extremely useful bit of information. I shall not go into this In detail since I have said enough on the entire subject to clarify the background of our procedure, without, I hope, introducing confusing facts. The problem,as you can see, is not an altogether simple one, and therefore you are quite right in wishing 0020310 A. G . Cerchione - (?.) - November 28, 1951 checlc your results from -cime to time. . . Cordially yours, S o b e r i l> Zenos # M X?* H E 0020311