Fasting blood was collected from all participants aged 8 years or older that participated in 1A Visit 2 and 2A Visit 2.
Blood was collected in various blood tubes, transported from the Lifelines location to the central lab in Groningen, centrifuged, aliquotted, and stored at -80°C on the day of collection.
From collection to storage, Lifelines adheres to stringent quality control protocols to ensure that the samples are fit for use in all standard blood analysis protocols. Detailed SOPs for all the steps described below can be requested from Lifelines if needed.
A subset of blood samples was used for standard blood analyses. The remaining samples were placed in long term storage to be used by scientists for future analyses.

All blood samples were collected before 10:00 AM.
Blood from fasting adult participants was typically collected using vacuum tubes instead of butterfly needles to avoid the activation of blood enzymes. Blood from fasting children (and in some exceptions from adults) was collected using less invasive butterfly needles.
Blood samples were taken from a blood vessel in the inside of the right elbow, where the veins are relatively close to the surface. In some exceptions the left elbow or the left/right wrist were used.

Multiple blood samples were collected in various types of plain glass Vacutainers® to enable all standard blood sample analyses.

• Serum samples are collected in vacutainers without any clot activators, anticoagulants, preservatives or separator material.
• Serum gel samples are collected in vacutainers with a gel composed of inert components, which are part of a polyester-based proprietary formulation. The gel forms a physical barrier between serum or plasma and blood cells during centrifugation.
• EDTA samples are collected in vacutainers with EDTA anticoagulants used to prevent clot formation both in vitro and in vivo, in order to maintain blood in the fluid state for hematological testing or to obtain suitable plasma for coagulation and clinical chemistry analyses.
• Heparin samples are collected in vacutainers with sodium heparin as an anticoagulant in order to prepare heparinized whole blood.
• Citrate samples are collected in vacutainers with citric acid, a reversible anticoagulant to enable coagulation assays.
• Buffy coat samples are collected from the fraction of an anticoagulated blood sample that contains most of the white blood cells and platelets, using density gradient centrifugation.
• PMBC's - peripheral blood mononuclear leukocytes isolated from whole blood.

All blood sample types except for PCMB's are available for virtually all participants that participated in 1A visit 2 and 2A visit 2.

All blood samples are aliquotted into 900ųl aliquots prior to storage.
Each aliquot is identified by a unique 2D code.

Aliquots are followed from creation to storage using the Tecan Freedom EVOware® Robot, a device that optimally combines pipetting, robotics and scheduling of multiple devices in a single package.

Lifelines adheres to stringent protocols and is able to provide for each individual sample detailed information about:

• the type of additive in the blood collection tubes
• sample processing times and temperatures
• hemolysis of the sample
• sample storage parameters
• the number of freeze-thaw cycles

During transport, blood samples must remain at a temperature between 0-8°C (cool) or 15-25°C (room temperature). This is checked using a LogTag temperature reader.