Last updated on 07 Dec 2020
Key cord blood banking information
The following information explains some of the key information about cord blood banking, including:
- important quality considerations for cord blood banking; and
- common terminology that you may encounter when considering cord blood banking.
Key points about collection
Collection of cord blood involves clamping and removing the cord and placenta as usual, then draining the blood from the umbilical cord and placenta. Delayed umbilical cord clamping (not earlier than 1 minute after birth) is currently recommended by NICE and WHO to allow more blood to reach the baby and help prevent anaemia. Banks can still collect high quality units of cord blood following delayed clamping. However, it is important that the cord blood is drained as soon as possible following delayed clamping to maximise the potential volume
To minimise the risk of contamination, it is important that the collection area is clean and fit for purpose. It is also important that the collector cleans the cord itself using correct aseptic technique.
To ensure the best quality collection, those collecting cord blood must be properly trained. Anyone collecting cord blood must act under the authority of an HTA licence.
Key points about transport
Time in transit should be kept to a minimum. Increased time in transit is related to increased cell death and can result in poor quality cord blood units (Fry 2013 and Querol 2010). Cord blood units should be cryopreserved (frozen) as soon as possible after collection and certainly within 72 hours (NetCord-FACT 2013).
Cord blood banks should ensure that cord blood units remain within validated parameters, which may include a defined temperature range that has been shown to maintain quality. Banks should use specific containers that have been demonstrated to maintain the appropriate temperatures and the integrity of the cord blood unit.
Key quality testing terms
Common methods for assessing the characteristics of a cord blood unit are explained here. You may encounter these terms when considering cord blood banking.
There is a risk that microbiological contamination could occur during cord blood collection, despite appropriate precautions being taken. Contamination could prevent the cord blood unit from being used in a transplant. Screening the cord blood for microbiological contamination before it is cryopreserved provides valuable information to the doctors selecting the unit for transplantation.
Total nucleated cell count (TNC)
There are many different types of cells in a cord blood unit, including stem cells and other cells. TNC refers to the total number of nucleated cells in a cord blood unit. TNC does not give specific information about the number of stem cells present.
A cord blood unit, like the circulating blood, is expected to contain mainly living cells and some dead cells. An assessment of viability estimates the proportion of living cells in a cord blood unit.
CD34+ cell count
CD34 is a molecule present on the outside of some stem cells. Cells that have this ‘marker’ are often referred to as ‘CD34-positive’ (written as CD34+). The number of CD34+ cells is used to estimate the number of stem cells in a cord blood unit. The presence of a high number of CD34+ cells is one of several factors indicating the suitability of a cord blood unit for transplantation.
Colony forming units (CFU)
For a cord blood unit to be useful, cells in a cord blood unit should be able to proliferate (increase in number) and differentiate (develop into different more mature cell types). A CFU assay is a way to assess the ability of the cells within the cord blood unit to proliferate and differentiate. Greater numbers of CFUs observed correspond to greater proliferative capacity of the cells in the cord blood unit. The different types of CFUs observed correspond to the potential of the cells in the unit to differentiate into those different cell types in the body. Some cord blood banks and transplant centres use CFU assays as part of their assessment of whether or not a cord blood unit can be used in a transplant.