THICK DROP — a method of detection of parasites of blood, and also identification of morphological elements krovp. It is offered by R. Ross in 1903 for identification of causative agents of malaria (see).
The method of a thick drop is used for identification of spirochetes (see), trypanosomes (see), microfilarias (see Filariases). It found broad application in medical practice since allows to investigate for the same time by 30 — 50 times bigger amount of blood on presence of parasites, than in a thin smear. It is caused by the fact that during the use of this method blood is not fixed and during coloring there is a hemolysis of erythrocytes, to-rye there are transparent, and parasites who are in them after coloring well visible. By means of this method the number of parasites on a certain quantity of leukocytes can be counted. In view of uneven distribution of parasites and leukocytes in various sites of the drug prepared by this method calculation should be made in the central and its peripheral sites and to output an average value.
At statement of a method identification of polychromophils (see the Polychromatophilia), eosinophils, basophiles, an endothelium (is possible at a long septic endocarditis and sepsis), metgemoglobinovy little bodies (Heinz's little bodies — Ehrlich).
Preparation of drug by a method of a thick drop: apply 2 — 3 drops of blood on a slide plate, to-rye distribute by means of a needle or a corner of a slide plate up to the size of a fifteen-cheap coin. Other method of preparation of drug was offered in 1925 by Huppenbauer: on
a slide plate do a blood smear and while it wet, apply on it a drop of blood, edges evenly spreads, forming the correct circle. Advantages of this method — uniformity of a drop, an exception of a bruise of elements of blood at its spreading; in a smear the stroma of erythrocytes remains that allows to study a form of N the size of the struck erythrocytes; the drop does not burst, well sticks to glass.
Drops of blood on glass dry up on air or in the thermostat and, without fixing, paint, is more often across Romanovsky (see Romanovsky — Gimza a method) at pH 7,2 — 7,3. Drug is recommended to paint not later than in 2 — 3 days after preparation. In drugs, it is long remaining, especially in the conditions of arid hot climate, parasites are painted worse, erythrocytes badly lyse. On such drugs for the purpose of ensuring hemolysis it is recommended to pour before coloring for 3 — 5 min. a distilled water, to-ruyu then replace with the painting solution.
Methods of the accelerated coloring of drugs are recommended by methylene blue and eosine. The drug prepared by a method of a thick drop can be also painted (after hemolyzing) by alkaline blue of Munson, and also by I. G. Ioffe's method methylene blue with ii fuchsin by other methods.
See also Gemogramm, Blood, methods of a research.
Bibliography: Laboratory methods of a research of pathogenic protozoa, under the editorship of D. N. Zasukhin, page 165, M., 1957; The Reference book on clinical laboratory methods of a research, under the editorship of E. A. Kost, M., 1975; Field J. W. The microscopic diagnosis of human malaria, v. 1 — 2, Kuala Lumpur, 1948 — 1956. H. A. Dyomina.