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Investigations of patient adverse reactions to transfusion
All transfusion reactions suspected to be caused by bacterial contamination of the unit must be referred to the National Bacteriology Laboratory through an NBS consultant for investigation.
When a transfusion reaction occurs, the hospital must report the incident to an NBS consultant who decides on the course of action. If the reaction is suspected to be caused by bacterial contamination, the hospital must first return the unit to the Centre from which the unit was issued. The unit will then be sent to the NBL for investigation. All associated units will be put on hold until further results are known.
Investigations include:
Testing of the implicated unit, investigation of the donor and molecular typing of isolates from the patient (if available), from the implicated pack and from the donor.
A report is compiled and sent to the Consultant Specialist for Transfusion Microbiology who will report back to the relevant hospital.
Investigations are reported into the UK Hemovigilance Scheme: Serious Adverse Blood Reactions and Events (SABRE) and Serious Hazard of Transfusion (ShoT)
For further information and request forms please click here.
Investigation of visually abnormal components
Visually abnormal components suspected of being bacterially contaminated are also investigated. This may be at the request of the local Processing or Issue department or at the request of the hospital before the unit is transfused. Units are investigated for reasons such as unusual colour, leaks, clots or unidentified lumps in the pack.
There are guidelines on the NBS website outlining the correct procedure hospitals must take when a transfusion reaction occurs or a contaminated pack is noticed.
For further information and request forms please click here.
Bacteriological screening of cord blood and autologous serum eyedrops
The blood from a baby’s umbilical cord is rich in stem cells and can be used to treat conditions such as leukaemia. The blood is taken from the cord just after the birth and is stored by the London Cord Blood Bank. The NBL screen each donation, using the automated blood culture system, before transplantation to ensure that it is not bacterially contaminated.
Some patients with certain conditions, for example those with keratoconjunctivitis, lose the ability to produce adequate tears, resulting in severe morbidity.
Autologous (i.e. patient’s own) blood is collected and the serum separated off and diluted with saline. This is then frozen for subsequent daily use by that patient as artificial tears. Prior to issue to that patient, each sample of artificial tears is screened for bacterial contamination.
Screening platelet concentrates to extend the shelf life to 7 days
In order to address supply problems caused by extended bank holiday periods, the NBS devised a strategy for the bacteriological screening of platelets to allow an increase in shelf life to 7 days. The screening enables the shelf life to be extended to 7 days, providing a microbiologically safer product.
Monitoring donor arm disinfection
Bacterial contamination of blood products by bacteria from the donor’s arm is associated with transfusion transmitted infections in patients. This is well documented in the literature.
The National Bacteriology Laboratory monitors the venepuncturist to ensure that the cleansing technique is being performed correctly and the current disinfection method is working effectively. This is done using agar contact plates on the donor venepuncturist site post disinfection.
Currently the National Blood Service uses Chloroprep Kit to disinfect the donor’s arm.
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