Numerous clinical studies have shown that the total number of Colony Forming Cells (CFCs) or Colony Forming Units (CFUs) in a CB unit is the one parameter that best correlates with the time to neutrophil and platelet engraftment, and overall survival following unrelated allogeneic CB transplantation. Several regulatory bodies (e.g. FDA, AABB, NetCord-FACT) recommend or require that the number of CFUs/CFCs in a CB unit be measured before cryopreservation and/or after thawing, prior to release of the unit to a transplant facility. Tools for standardization of the CFU/CFC assay include semi-solid methylcellulose-based medium, specialized cultureware and an instrument for automated counting of CFU/CFC assays.

Prasad et al. ; Blood 112: 2979-2989, 2008

In unrelated CB transplantation, total CFC numbers after thawing of CB units correlated more strongly with recovery and survival than other parameters, such as TNC counts and CD34+ cell numbers (including CFC numbers before cryopreservation) 

The AABB made a recent revision to their guidance document (4th edition of the AABB Standards for Cellular Therapy Product Services, reference standard 5.17B no. 4), requiring all AABB-accredited cord blood banks (i.e. – public and private) to perform the CFU assay on any units that are to be released for transplantation.

The official wording from AABB is:

The following tests shall be performed any time before distribution: CFU or equivalent functional assay for any product.

STEMCELL™ Technologies has developed the MethoCult™ methylcellulose-based medium - the world CFU gold-standard method.