Blood samples given from both cases and controls in the EIMS study are sent to the Biobank located at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet. At the biobank DNA samples are extracted from the blood samples which is thereafter frozen and stored until they are needed in the data analyses.

To extract the DNA from the blood samples they must first be centrifuged. During this process the blood is stratified into three layers; red blood cells on the bottom of the tube, a gel in the middle and the blood plasma on top. The plasma is aliquoted into smaller test tubes and the blood pellet is retrieved through chemical DNA isolation of the blood cells.

After the blood sample has been processed, the plasma and the blood pellets are placed in a freezer. The plasma and blood pellets are vulnerable at room temperature and must therefore be frozen directly after the extraction.  

The extracted DNA samples are stored in special freezers which are kept at -80° Celsius (-112° Fahrenheit). The freezers are connected to emergency generators to insure that the samples are not destroyed due to power shortages. There are also special back-up holdings available which can be used in case the freezers break down.

Once the DNA samples have been aliquoted, numerous small test tubes have been generated for each study participant. The samples must therefore be properly labeled and stored in the correct order so that they can be identified later for analysis. The placement order of the samples is noted in a digital database at the Biobank so that specific samples can easily be found in the freezers when needed.  

When it is time to extract data from the DNA samples they are taken out of the freezers and prepared for analysis.

The analyses on which gene variations that affect the risk of developing MS are done using specially designed computer programs. It is not possible for the researchers to identify risk levels for an individual since both genes and the environment together affect the risk of developing MS. The researchers instead work towards identifying general risk factors that can be applied at a population level.