The multi-facets of tuberculin standardization

Some parameters affecting the standardization of a tuberculin preparation have been evaluated and it has been shown that: 1) The loss of tuberculoprotein on the surfaces of containers is in the order of 0.15 mug/cm2 and the 0.18 mug/cm-2 for glass and plastic surfaces respectively, and that this loss can be prevented by the addition of a nonionic anti-adsorption agent such as Tween 80. 2) For non-stabilized tuberculin PPD solutions the losses of PPD due to adsorption increased linearly with the Surface to Volume ration. 3) Exposure to light had a deleterious effect on tuberculin PPD decreasing its biological potency and altering its appearance. This effect increased with the dilution of the tuberculoprotein solution, and can be prevented by storing the tuberculin in amber containers. 4) The potency of tuberculoprotein was dependent on its molecular weight, and the % distribution of tuberculoprotein molecules of different molecular weight varied from batch to batch. This variation can be eliminated by preparing a large batch of tuberculin in a dried form sufficient to fill the demand for many years to come. 5) The route of injection and the species or strains of mycobacteria used for sensitization of guinea pigs affected the relative potency of a tuberculin preparation. 6) The size of a tuberculin skin reaction increased as the volume of tuberculin injected intracutaneously into sensitized guinea pigs was increased although the number of tuberculin units administered was the same. 7) The sizes of skin reactions to certain doses of tuberculin was affected by other doses of tuberculin being injected simultaneously at other sites. 8) Sex and age of guinea pigs affected the size of the tuberculin skin reaction. 9) The genetic make-up of the test animals affected the relative potency of a given tuberculin preparation. 10) Racial differences among various populations might account for different levels of tuberculin reactivity to a given tuberculin preparation. It is hoped that this work has made us aware of the many problems which can be encountered in standardizing tuberculin and it is also to be hoped that the solutions we have offered to some of these problems can be useful to those attempting to standardize allergens other than tuberculin.