In Vitro Glycation
Canterbury Scientific Ltd can produce the abnormal level (Level 2) HbA1c control by a process of controlled in vitro glycation of non-diabetic blood. This means there is not a reliance on sourcing blood from diabetic subjects with high HbA1c levels, and it also means that levels of up to over 20% can be produced if required. It also avoids the potential ethical issues relating to obtaining blood from a patient with a clinical condition.
In vitro glycation essentially glycates the same amino acid residues as are glycated in the native glycated hemoglobin. But the ratio of α:β chain glycation is higher in the in vitro product. This means that there is an increase in the proportion of glycation at sites other than the HbA1c site. This makes no difference in procedures such as ion exchange HPLC, or immuno assay where the analytical method specifically measures the HbA1c directly (i.e. measures the glycation of the β N-terminal valine). However it means that with glycation specific type assays such as the boronate affinity method the calculated HbA1c figure (with the increased proportion of glycation at sites other than the HbA1c site) will be higher than when the same glycated sample is measured on the 2 other method types. The normal level control is unaffected since it has been glycated in vivo.
Stability of Hemoglobin Controls
The stability of a quality control product is critical. A good control should continue to give the same result on repeated analysis during the defined life of the control, and must be stable throughout manufacture, transport, distribution and storage.
Degradation of protein occurs as a result of chemical and free radical reactions. The integrity of the control can be damaged from a poorly designed lyophilisation protocol, through repeated freezing and thawing, or as a result of microbial growth. It is important during the design that unwanted reactions and conditions are identified and the production and formulation is planned so that these reactions are inhibited or their rates dramatically reduced. It is also important that any protective additives do not interfere with the analytical methods.
Our controls have been carefully formulated to include a number of protectants and stabilisers that preserve the proteins in their native conformation, resulting in products with exceptional stability of both closed and open vials.