The standardization of tuberculin / C.C. Okell and H.J. Parish.

  • Okell, C. C. (Charles Cyril), 1888-1939.
Date:
[1927?]
Catalogue details

Licence: In copyright

Credit: The standardization of tuberculin / C.C. Okell and H.J. Parish. Source: Wellcome Collection.

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    2S represents a significant difference. If the doses are such that the mortalities symmetrically disposed around 50 %, s = ioo ^/2p C. p) are expressed as % mortality, where p is the probability of death with the smaller and survival with the larger dose and N is the number of animals in each group and— 100-28 1AA -o-= 100p, and from this it can be shown that— P =*± f 2JV + 4' 100p is the percentage rate of' mortality given by one dose and 100 (1 - p) is the percentage rate of mortality just significantly different. The doses which correspond to these mortalities are read from the mortality curve (Chart 1) and the ratio calculated for different values of N. It is of course clear that all these calculations depend on the accuracy with which the curve (in Chart 1) represents the true relationship between mortality and dose. The number of observations is not large and there is a possibility of error in the estimates of the ratios calculated from it, but the calculations give an idea of the order of accuracy of the test. SUMMARY. The intradermic test is more accurate than the subcutaneous or von Pirquet methods, differences representing a 40% drop being almost always detectable on a small series, and finer differences on a larger series of guinea- pigs. The test, however, calls for considerable experience. The subcutaneous test will also show differences of 40-50%, if a sufficient number of suitable guinea-pigs is used, but the cost in guinea-pigs of attaining a given degree of accuracy is much greater than with the intradermic test. Its one advantage is that there is practically no personal factor in its interpretation. The von Pirquet test in guinea-pigs is very inaccurate and gross errors are often made. It is practically useless as a method of standardizing tuberculin. We have to thank our colleague, Dr. J. W. Trevan, for much help and criticism in this work. DEFERENCES. Aronson, J. D.—(1926) Amer. Rev. Tuberculosis, 5, 263. Calmette, A., and de Potter.—(1926) Ann. de VInst. Pasteur, 40, 353.—(1926) League of Nations' Report (C. H. 429), Geneva. Eagleton, A. J., and Baxter, E. M.—(1923) Brit. J. Exper. Pathol., 1923, 4, 289. Otto, R., and Hetsch, H.—(1921) “Die Staatliche Priifung der Heilsera und des Tuberculins,” Arb. a. d. Staatsinst. f. exper. Therap. zu Frankfurt, Heft 13, Jena. Trevan, J. H.—(1927) Proc. R. Soc. (in the press). ALLARD AND SON, LIMITED, LONDON AND DORKING,
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