Method for determining agglutination

1. A method for determining agglutination of a tested biological liquid by measuring a change in a hydrodynamic resistance of the tested biological liquid flowing through a microfluidic reaction channel of a microfluidic device, the method comprising the steps of:

a) calibrating the microfluidic device by calculating a calibrated value of the hydrodynamic resistance of a sequence of droplets of a known biological liquid in which agglutination occurred and a calibrated value of a sequence of droplets of the known biological liquid in which agglutination did not occur, according to steps from (b) to (i) and next performing the steps from (b) to (i) for the tested biological liquid;

b) filling the microfluidic reaction channel with a hydrophobic continuous liquid phase, the microfluidic reaction channel having detectors spaced at a distance defining a measurement section of the microfluidic reaction channel, wherein the microfluidic reaction channel is configured such that the pressure inducing the flow in the microfluidic reaction channel is a difference between a pressure over the reservoir with the continuous phase and an atmospheric pressure;

c) introducing into the microfluidic reaction channel a first reference droplet being a droplet of the biological liquid merged with saline or PBS or water and immiscible with the continuous phase;

d) causing the first reference droplet to flow through the microfluidic reaction channel having a measurement section;

e) measuring a time of flow of the first reference droplet through the measurement section of the microfluidic reaction channel;

f) introducing into the microfluidic reaction channel a second reference droplet being the same as the first reference droplet, followed by a sequence of 1 to 1000 test droplets, wherein the test droplets comprise an agglutination reagent and the biological liquid which is the same as the biological liquid comprised in the first reference droplet and in the second reference droplet, and wherein the test droplets are immiscible with a continuous phase;

g) causing the second reference droplet and the sequence of the test droplets to flow through the microfluidic reaction channel;

h) measuring a time of flow of the second reference droplet through the measurement section while the sequence of the test droplets is present in the microfluidic reaction channel;

i) calculating the hydrodynamic resistance of the first reference droplet and of the second reference droplet being followed by the sequence of the test droplets, on the basis of the times of flow measured in steps (e) and (h); and

j) comparing the value of the hydrodynamic resistance of the first reference droplet with the value of the hydrodynamic resistance of the second reference droplet being followed by the sequence of the test droplets, and determining that agglutination occurs in the sequence of the test droplets of the tested biological liquid if the value of the hydrodynamic resistance of the second reference droplet being followed by the sequence of the test droplets is increased as compared to the value of the hydrodynamic resistance of the first reference droplet.

2. The method according to claim 1 wherein the continuous phase separates the droplets from a wall surface of the microfluidic channel.

3. The method according to claim 1 , wherein the continuous phase is selected from the group consisting of hexadecane fluorized oil and mineral oil.

4. The method according to claim 1 , comprising introducing into the microfluidic reaction channel two reference droplets having the same volume.

5. The method according to claim 1 , wherein the sequence of the test droplets is introduced into the microfluidic reaction channel after the second reference droplet has traveled a distance of from 10 to 20 widths of the microfluidic reaction channel.

6. The method according to claim 1 , wherein the test droplets have a size of from 3 to 4 widths of the microfluidic reaction channel.

7. The method according to claim 6 , wherein a distance between the test droplets introduced to the microfluidic reaction channel is from 2 to 5 widths of the microfluidic reaction channel.

8. The method according to claim 1 , wherein the tested biological liquid is a sample of a whole blood, plasma, serum or isolated corpuscles.

9. The method according to claim 8 , wherein for blood typing, the agglutination reagent comprises monoclonal antibodies selected from the group consisting of blood group system antibodies which are anti-A, anti-B and anti-D antibodies.