Blood sampling and DNA sequencing

During DIS-III, blood samples were collected for DNA isolation and sequencing, a full blood count and analyses of markers of iron metabolism. These blood samples were taken when the donor visits the blood bank to donate. Donors who stopped donating were invited separately.

DNA

DNA will be isolated, analysed and stored from these blood samples. A part of or the entire genome will be analysed, including high-throughput genotyping using the UK Biobank Axiom® Array (ThermoFisher, CA, USA). There are 820,967 SNP and indel markers on this array, which is currently used in the UK to genotype 450,000 individuals from the UK Biobank, 50,000 individuals from the INTERVAL study and another 50,000 samples of the NIHR BioResource.

Full blood count

A full blood count (Model XT-2000, Sysmex) was performed within 24-hours after blood donation in order to get data including white blood cell count, red blood cell count, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, platelets, red cell distribution width, platelet volume, platelet distribution width and reticulocyte haemoglobin. The full blood count was used to determine haemolysis one month after donation.

Iron metabolism

Besides haemoglobin (measured as part of the full blood count), ferritin and zinc protoporphyrin (ZPP) levels are measured. Ferritin is an indirect measure of body iron stores and is measured in plasma. In case of decreased iron availability, stored iron will be used to form heme. This may result in declining iron stores. Ferritin levels below 15 µg/L are diagnostic of iron deficiency. ZPP (Hematofluorometer) is measured in whole blood within 10 days after donation. ZPP levels are expected to increase in case of iron deficiency, because zinc then replaces iron in the synthesis of heme.