Microbiological screening for stem cell cryopreservation

Infective agents, particularly viruses, can be transmitted through stem cell preparations as through blood products and may cause significant morbidity and mortality in the recipient. It has been demonstrated that transmission of hepatitis B virus has occurred following common storage in a liquid nitrogen tank which contained one patient's hepatitis BsAg +ve bone marrow.

The following tests should be performed on all patients in whom it is planned to cryopreserve stem cells

• Hepatitis B surface antigen.

• Hepatitis B surface antibody.

• Hepatitis B core antigen.

• Hepatitis B core antibody.

Hepatitis C antibody.

• HIV 1 and 2 antigen. 3fl8 • HTLV1 antibody. 308 • VDRL.

• Additional serum for storage for retrospective analysis.

These results must be available to transplant laboratories before cryopreservation. Since many of these patients will be receiving blood products as part of their on-going treatment, they must be performed within 30 days of cryopreservation to prevent false -ve antibody tests due to the interval between exposure and seroconversion. In practice these constraints dictate that samples should be taken between 7 and 30 days prior to cryopreservation.

Patient samples shown to be -ve for all the above infectious agents should have stem cells stored in a dedicated liquid nitrogen freezer conventionally in the liquid phase.

Patient samples shown to be +ve for any of the above agents should be double bagged and stored in a separate liquid nitrogen freezer in the vapour phase (to reduce transmissibility). Data on all stem cell product samples must be registered in a secure environment on a computerised database with a logical inventory and retrieval system. No material should be imported to the freezers unless a complete negative virological audit storage trail can be demonstrated.

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