The method of sampling blood in the form of small droplets on a filter paper has already been known since the 1960s – since Robert Guthrie developed a test for screening of newborns for signs of phenylketonuria. By now, this so-called dried blood spot (DBS) analysis is applied for the diagnostics of diverse hormonal and metabolic diseases in newborns all over the world. The early detection of these disorders is fundamental for their timely, often life-saving therapy.
Especially the non-invasive intervention for collecting the sample is a major advantage of the dried blood spots. Not even a physician is required. Moreover, most analytes remain stable within the dried blood for weeks, so the sample can be simply transported at room temperature. A cool and dry surrounding is recommended for longer storage – ideally in the fridge. The dried blood spots pose a very low risk of infection for the laboratory staff who handle the samples
For these reasons, DBS analysis is not only excellently suited for the newborn screening , but also particularly qualifies for serological diagnostics of infectious or autoimmune diseases, for example in regions which are difficult to access and exhibit sparse medical infrastructure. In addition, DBS analyses are well suited for health-conscious persons for the purpose of disease screening and monitoring. Due to the autonomous blood sampling, anywhere at any time, DBS provide individual access to a broad spectrum of laboratory analyses.
Blood sampling and extraction of dried blood spots
The procedure of blood sampling and extraction is very simple:
By means of a lancet, the fingertip (or the earlobe) is punctured and a blood droplet is spotted on a carrier material, e.g. prefabricated filter paper (PerkinElmer #226). Afterwards, the dried sample is sent to a laboratory where it is processed. A circle of predefined size is punched out of the center of the dried blood spot and the small platelet is transferred into an empty, uncoated reaction vessel (e.g. a microplate).
Also, EUROCheck may be used as alternative to filter paper. This sample carrier in card form was specifically developed for easy and fast blood sampling at home. Three platelets are positioned at both short sides of the card on which the blood has to be trickled. The card is subsequently sent to a laboratory where the blood filled platelets are removed and transferred into an uncoated reaction vessel (in analogy to the filter paper).
In the reaction vessel, the dried blood is extracted from the material using a defined volume of sample buffer. The resulting extract corresponds to a diluted blood sample and can be applied in the respective ELISA or immunoblot system for the requested analysis.
The feasibility of using dried blood spots as starting material for serological analyses has been shown for numerous EUROIMMUN ELISAs and selected line blots. Beyond that, some test systems are registered with the CE mark: ELISA and EUROLINEs for the diagnostics of Lyme disease as well as Anti-CCP ELISA (IgG; rheumatoid arthritis) and Anti-Gliadin (GAF-3X) ELISA (IgG; coeliac disease). Feasibility studies for further test systems are in process and can be initiated upon request.