True Serum (“Off the Clot”)
Whole blood is collected without anticoagulant in FDA licensed blood centers located in the USA and allowed to clot naturally. The red cells are then separated and the clot discarded, leaving the serum which is used primarily as a base for kit calibrators and controls. Serum is usually provided as single donations (~250ml) but can also be pooled and filtered. Single donations allow specific demographic requests (such as gender, age, race, geographic, smoker) and even illness/medication specifications.
There are three methods for manufacturing plasma. All methods start with whole blood collected in FDA licensed blood centers in the USA.
- Sourced Plasma is collected on Sodium Citrate anticoagulant and centrifuged bedside, returning the red blood cells immediately to the donor. This method allows for larger volumes per donation (~600-880ml) and the plasma is also frozen quickly (within 1-2 hours) which helps preserve labile proteins and enzymes.
- Recovered Plasma is a byproduct of whole blood collected for transfusion on CPD anticoagulant and separated from the red blood cells by centrifugation. The unit volumes are ~200ml but it is much more cost-efficient than Sourced Plasma. Recovered Plasma is normally supplied in large pools (up to 500L).
- Special Anticoagulant Plasma is required by manufacturers who want their control or calibrator to exactly match the anticoagulant used in their assay’s specimen collection tube, such as Lithium Heparin, K2 EDTA, K3 EDTA, Sodium Heparin, etc. Whole Blood is collected into dry bags with the specific anticoagulant added, then centrifuged and the red blood cells discarded. The plasma is normally frozen as single donations (~250-300ml) but can also be pooled into large lots upon request.
Defibrinated plasma is created by forcing sourced or recovered plasma to clot by removing the anticoagulant and/or adding clotting factors. This product is often referred to as serum (the only difference is that it didn’t clot naturally). Most controls and calibrators use pooled defibrinated plasma (up to 500L per lot) because it is more stable than plasma and much cheaper than true serum. Stability is often further improved by removing the lipids, allowing multiple freeze-thaws.
When using plasma or serum as a base matrix for controls or calibrators, it is very helpful to remove certain analytes from the matrix before adding antigens (to improve stability), or when creating the zero level calibrator or low level control. Cantor BioConnect uses multiple stripping methods to remove almost any desired analyte including Vitamin D, hormones (T3/T4, Estradiol, Progesterone, FSH, etc.), cancer antigens, cardiac markers and IgG/IgM (Rubella IgG, etc). These analytes can be stripped down to undetectable levels even by Mass Spec. Most of Cantor BioConnect’s analyte-free serum is also delipidated for added stability and ease-of-use.