Landis test (E.M. Landis; synonym for Landis - Gibbon test) is a method for determining capillary permeability. The method is based on the idea of the existence of a certain relationship between the magnitude of the hydrodynamic pressure inside the capillary and the permeability of the capillary wall. Measuring the magnitude of capillary filtration and comparing it with capillary pressure shows that the amount of filtered and resorbed fluid in the capillaries is directly proportional to the difference between hydrostatic and colloid osmotic pressure. Landys et al. have shown that with an increase in venous, and hence capillary pressure, an increase in capillary filtration occurs.
The method of testing Landis is as follows. The patient is in a horizontal position. With the help of the Riva-Rocci apparatus with a pressure in the cuff of 40 mm Hg. Art. create a venous congestion in the hand of the subject for a duration of 30 minutes, after which they take blood from the cubital veins of the "stagnant" and "non-durable" hands. In blood samples taken, hematocrit determines the volume ratios of plasma and erythrocytes, and in plasma, the content of total protein and its individual fractions.
The increase in the volume of erythrocytes in the blood from the "stagnant" hand compared to the blood from the "non-congestive" hand indicates a thickening of the blood resulting from the release of a certain amount of liquid blood (capillary filtrate). The difference between the amount of protein in the blood "stagnant" and "non-congestive" can be judged on the degree of capillary permeability to blood proteins.
The permeability of capillaries is characterized by two indicators - a capillary filter and loss of protein. Capillary permeability can be considered normal if the amount of capillary filtrate does not exceed 3-4 ml (according to some authors, up to 5 ml). The capillary filtrate in these cases either does not contain protein at all, or its content does not exceed 0.1%. With increased capillary permeability, filtration of an increased amount of fluid containing one or another amount of protein occurs.
Landis's sample was used by many domestic authors. Most assess it positively. Landis's test, firstly, makes it possible to obtain a digital expression of permeability, and secondly, when it completely eliminates the inflammatory response, which increases the permeability of capillaries. Modifications of the Landis sample were proposed by G. P. Artynov and E. D. Semiglazova, V. P. Kaznacheev.