Pirquet Reaction

PIRQUET REACTION (Pirquet), a skin reaction to tuberculin, proposed by Pirquet in 1907. It is used to study tuberculin allergy, i.e., increased sensitivity to tuberculin in persons infected with tubercle bacilli. The essence of the Pirquet method is that tuberculin is applied to a scarified area of skin, and after a certain period, inflammatory changes in the skin at this site are recorded (see also Skin reaction). When studying smallpox vaccinations, Pirke found that in persons who had already been vaccinated, the reaction to revaccination appeared early, within the next 24 hours. An early reaction therefore serves as proof of vaccinal allergy. Pirke utilized skin vaccination to establish previous infection with tuberculosis. The increased sensitivity of the tuberculous organism to tuberculin manifests itself in the fact that the skin of such an organism responds to the tuberculin penetrating it with characteristic inflammatory phenomena, whereas the skin of a healthy person does not show such reactions. Original Pirque technique. The skin of the forearm is wiped with wool soaked in ether; then 2 small drops of tuberculin are applied at a distance of 10 cm from each other using an eye dropper. Then, using a special platinum-iridium lancet heated over a flame, the skin is punctured in the middle between both 72fr drops (control reaction); in the same way, mechanical traumatization of the skin is performed under both drops of tuberculin. After this, several fibers of sterile degreased cotton are placed on both drops to prevent the drops from running off. After 5 min., the tuberculin is wiped off, but in such a way that it does not get on the control reaction. Petruschky (1908) uses a smallpox vaccination lancet instead of the lancet, making a superficial incision on the skin. Nastyukov (1922) proposed a platinum scarifier. According to the instructions of the II All-Union Tuberculosis Congress and the II All-Union Congress of Pediatricians in 1923, skin sensitivity to a series of tuberculin dilutions is studied, namely, besides whole tuberculin, to its 30%, 10%, and 3% solutions. Thus, besides the degree of intensity of the reaction to whole tuberculin, the lower limit of sensitivity to weak tuberculin solutions is also determined. Composition of the liquid for the control reaction: 100 cm³ of physiological solution, 0.5 carbolic acid, and 5.0 glycerin. This same liquid is used for diluting tuberculin. Since the meat-peptone glycerin broth usually used for obtaining tuberculin in some cases itself causes certain reactive phenomena on the skin, it is better to use as the "control" liquid a meat-peptone glycerin broth with the addition of 0.5% carbolic acid. Measurement of reactions. The results of the P.r. are also attempted to be measured quantitatively. For this, the diameter of the inflammatory infiltrates appearing on the scarifications is determined [see separate table (pp. 223-224), Figure 2]. If an infiltrate appears from the control solution, it is also measured. Besides the size of the infiltrate in millimeters, the morphological features of the local reactive inflammation should also be noted in the protocol, such as the presence of serous exudate (large and small vesicles), diffuse hyperemia, the appearance of crusts, necrosis, desquamation, pigmentation. General temperature and focal reactions are rarely observed with the Pirquet method. The results of the skin reaction are conveniently assessed after 48 hours; in case of a negative reaction, it should be repeated immediately. When assessing the results of the repeated examination after 48 hours, the results of the first examination should be checked simultaneously. The main criterion for a positive reaction to tuberculin is the size of the papules on increasing concentrations of tuberculin. If on all concentrations of tuberculin almost identical papules are observed, even if reaching a size of 5 mm, the reaction cannot be considered positive. A positive skin reaction to tuberculin is any infiltrate whose diameter clearly exceeds the diameter of the non-specific infiltrate obtained from the control solution. A number of authors disputed the strict specificity of skin reactions to tuberculin. The opinion was expressed that the reaction of the healthy and tuberculous organism to tuberculin represents only a quantitative difference, i.e., for the tuberculous person tuberculin acts as a stronger irritant than for a healthy one. Zieler, however, insists on the specificity of tuberculin reactions. According to his data, subjects free from tbc do not give skin reactions to tuberculin and other preparations from BK (Zieler considers those free from tbc who do not give general and local reactions to doses of 50-1000 mg of old Koch's tuberculin under the skin). On the contrary, both tuberculous and non-tuberculous people give a positive reaction to other bacterial preparations (intestinal bacillus, dysentery bacillus, etc.). Most clinicians believe that a positive skin reaction to tuberculin reliably indicates infection with tbc. A negative skin reaction to tuberculin cannot be considered proof of the absence of tuberculous infection in the body. To finally determine the degree of tuberculin allergy in the presence of negative skin reactions, it is necessary to resort to tuberculin diagnosis by intracutaneous and subcutaneous tests (method of determining the tuberculin titer). A single P.r. has almost no significance for assessing the course of the tuberculous process; repeated observation is much more valuable in this respect. In children, for example, more intense reactions to tuberculin correspond to fresh and acute manifestations of the process (allergic stage), but as the process passes into the stage of isolated phthisis, their intensity decreases. The practical significance of P.r. for the diagnosis of tbc is mainly in childhood.

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