USE OF EDTA TUBE WITH GEL IN ELISA METHOD

The invention relates to the blood tests performed by means of Micro and Macro Elisa method.

The invention relates in particular to the use of EDTA tube with gel in said blood tests performed by means of Micro and Macro Elisa method and thus obtaining the sample as the plasma.

The use of EDTA tube with gel and thus obtaining the sample as the plasma according to our invention eliminates the erroneous results caused by inadequate sampling leading to test errors in the auto analyzers and/or the loss of material and kit caused by the inability to take any sample at all.

State of the Art:

The term ELISA is the abbreviation for "Enzyme Linked Immuno Sorbent Assay" test. It is a quantitative measurement method based on examining the antigen-antibody relation and the activity of an antibody-bound enzyme.

In the method mentioned above, it is possible to search the antibody against the antigen or the antigen against the antibody wherein said method is also a diagnosis method used for the virus and parasite infections. Here, noncompetitive indirect staining method is employed by the use of the immobilized antigen.

ELISA method was discovered in 1960s as an alternative to "Radioimmunoassay" methods and the use thereof has spread wideworld ever since.

Due to the longevity of the reagents employed in ELISA method and the absence of a radiation hazard associated with the waste materials, ELISA rapidly become the method preferred over RIA (Radioimmunoassay) method.

One of the most important advantages of ELISA method is that it provides the ability to work with a great number of samples within a short time in the diagnosis laboratories. Upon the productions becoming widespread parallel with increasing usability of these tests, there was a reduction in their costs. For this reason, it is frequently used in many hospitals and laboratories, since it yields reliable and economical results. From past to present, Macro and Micro ELISA assays have been performed from the "Serum", the blood liquid, in Turkey and numerous countries of the world.

Serum is the name given to the light colored yellowish liquid that remains when the fibrinogen and platelets combine in the form of a dark colored mass of clot once the blood has lost its homogeneous structure after it has been kept to enable the clot formation. (In practice, in ELISA studies, this clotted portion and the shaped blood components remain in the bottom of the tube, while the fibrin clot remains within the serum.)

The blood clots a certain period of time after it is taken from the body and placed into a glass container. This condition results from the conversion of the plasma protein, which is present in dissolved state within the blood and which is referred to as fibrinogen, into the insoluble fibrin. The cells in the blood remain within this fibrin. A light colored yellowish liquid emerges as a result of the contraction of the fibrin and this liquid is called the serum.

The liquid obtained by the separation of the cell members from the unclotted blood is called the plasma. Whereas serum does not contain fibrinogen and some other coagulation factors, said substances are present within the plasma.

The antibody search in the ELISA method is performed in several ways.

These are as follows:

• Known antigen is adhered to a plastic surface. For Micro-Elisa system, this antigen is coated on the surface of the wells made for being used for each patient. The patient serum where the antibody is to be sought is placed into these wells. A certain period of time is allowed to elapse and washing is performed. In case the corresponding antibody is present in the serum, it combines with the antigen.

• Human globulin antiserum marked with an enzyme is added. A certain period of time is allowed to elapse and washing is performed. In case the serum under examination contains the antibody that matches the antigen, it will become bonded to the antigen, hence it will bind also this last added enzyme- marked human antiglobulin and it will not be possible to be removed by way of washing.

• A suitable chromogenic substrate is added to the enzyme. The color that appears when the system-bound enzyme breaks down this substrate will be measured by means of colorimetric methods and will give an idea about the bound enzyme and hence the bound antibody.

Since Macro and Micro ELISA assays are currently performed based on the blood liquid, i.e. the "serum" that also contains fibrin clots, in Turkey and numerous countries of the world, many associated disadvantages come into the picture. Namely:

The fibrin present in the serum forms clots in the blood samples due to the inadequate centrifugation or the biochemical properties of the patient/donor and said clots lead to the blockages or insufficient serum withdrawals in the probes of the auto analyzer during the assay.

The device stops operating in cases of probe blockage and causes unnecessary time loss and material consumption.

As for the insufficient serum withdrawals, the device may not detect the sampling of the serum and it keeps running in case the control mechanism of said device is inadequate. Since the device is not able to take sufficient serum, it causes erroneous test results. It may give negative result for a positive sample. This is an unacceptable and irreversible condition particularly for the blood centers.

No matter how much the aforementioned disadvantages are tried to be prevented today, it has not been possible to obtain an exact achievement. The method of solution commonly employed today is a method developed based entirely upon the technician (human).

In this regard, the blood samples subjected to centrifugation are visually inspected and fed into the device by the technician. However, since a criterion for the stages of clotting is either absent or is not used, the fibrin clot may form also while the serum sample is in the device.

For Macro ELISA methods, the device issues Exception warning and stops to operate in case it is not able to take the desired amount of serum. The clot is removed by a staff visually monitoring the fibrin inside the serum and the assay is repeated. Every defective pipetting which may not be controlled by the machine and thus for which the machine continues to operate becomes diluted during the assay and the assay is terminated. The obtained result is confirmed by the specialist.

Our invention is an application that eliminates all the aforesaid disadvantages and the corresponding erroneous measurements and enables pipetting the necessary quantity of sample and the performance of an error-free measurement/test, said application aiming to enable the use of EDTA tubes with gel in said blood tests performed by means of Micro and Macro Elisa method and thus to enable the sample to be obtained as the plasma.

The term EDTA is the abbreviation for ethylene diamine tetra acetic acid. EDTA is a polyamino carboxylic acid compound. EDTA was first described by Ferdinand Munz. Munz achieved the discovery of EDTA from ethylenediamine and chloroacetic acid solutions.

Since the EDTA tubes with gel contain anticoagulant agent, no fibrin clot forms from fibrinogen within the tube during the procedure. Our invention enables to avoid the erroneous measurements and detections in the serums with fibrin clot as well as enabling an error-free detection and measurement. Since the existing EDTA tubes do not have a gel barrier, the shaped blood components may become broken down in time, leading to haemolysis, which in turn deteriorates the plasma quality.

Moreover, in the EDTA tubes with gel, the duration and number of revolutions of centrifugation required to obtain the plasma are less than those for the serum tubes.

As mentioned above, our invention eliminates the erroneous or defective sampling in ELISA assays.

Another feature of our invention is the elimination of the loss of material being used. Since there is no loss of material, savings are obtained in time and labor. The efficiency reaches 99.99% in ELISA assays.

With our invention, a precise test result is enabled to be obtained depending on the sensitivity of the kit.

Another feature of our invention is the prevention of the contamination risk in cases where disposable pipettes are not used. In the assays made with serum, the teflon coated pipettes may transmit the fibrin smear to the next sample when they contact the fibrin clot and thus cause contamination to adversely affect the efficiency.

Description of the Invention:

According to our invention, EDTA tube with gel is used in said blood tests performed by means of Micro and Macro Elisa method.

Said assay tube mentioned in our invention contains EDTA (Ethylene Diamine Tetra Acetic Acid) substance and the gel.

Since said blood tests performed by means of Micro and Macro Elisa method are conducted using EDTA tube with gel according to our invention, the result of the assay is obtained as plasma.

EDTA (Ethylene Diamine Tetra Acetic Acid) is an anticoagulant agent. Since the assay sample in the tube is obtained as plasma after the centrifugation in the machine/device, it does not contain fibrin clot.

Since the tube according to our invention contains gel, the shaped components remain under the gel after the centrifugation and they do not mix into the plasma. In this way, the errors are removed from the assay sample; hence the factors that would block the probe of the auto analyzer are not present in the assay sample. This leads to the reliable test results to be obtained and also an economic gain to be provided owing to the absence of the material or kit loss.

Since said blood tests performed by means of Micro and Macro Elisa method are conducted using EDTA tube with gel according to our invention, the deficits in the technical equipment of the machine and the devices into which the tube is positioned do not threaten the reliability of the assay.

Since said blood tests performed by means of Micro and Macro Elisa method are conducted using EDTA tube with gel according to our invention, the fibrin plots originating from serum are not present and therefore the factors originating from the sample that would threaten the test are eliminated.

Since said blood tests performed by means of Micro and Macro Elisa method are conducted using EDTA tube with gel according to our invention, the material and kit losses are reduced to zero and an economic gain is obtained on national and corporate basis.