Haemovigilance and SHOT

The interest in transfusion-transmitted infections has meant that transfusion medicine has developed significantly and great emphasis has been put on quality, audit and good manufacturing practice (GMP). However, there were no surveillance systems in place to assess the incidence and prevalence of transfusion risks. France instituted the first system of national haemovigilance in 1994. Haemovigilance is defined as 'the set of procedures of surveillance organized from the collection of blood and its components to the follow-up of its recipients, with the purpose of collecting and evaluating information on the undesirable and unexpected effects resulting from the use of blood products and of preventing their occurrence'.

SHOT (Serious Hazards of Transfusion), the UK haemovigilance system was introduced in 1996 (Figure 16.4). SHOT receives reports of major adverse events surrounding the transfusion of single or small pool blood components supplied by the UK National Blood Services (red cells, platelets, FFP, methylene blue-treated FFP and cryoprecipitate). It does not cover complications of fractionated plasma products except for some incidents related to anti-D Ig administration. It is a confidential and anonymized scheme of voluntary reporting, though the

Figure 16.4 Cumulative data from 6 years of UK Haemovigilance (SHOT) reporting, 1996/97 to 2001/02. Completed questionnaires received, by transfusion incident, 1996/97-2001/02 (n = 1630).

European Directive will make reporting mandatory. Hospitals report events under the following categories:

• incorrect blood component transfused (IBCT), regardless of harm to recipients;

• acute transfusion reaction (ATR) within 24 h;

• delayed transfusion reaction (DTR) beyond 24 h;

• transfusion-associated graft-versus-host-disease (TA-GvHD);

• transfusion-related acute lung injury (TRALI);

• post-transfusion purpura (PTP);

• transfusion transmitted infection; (TTI) comprising

- bacterial contamination;

- post-transfusion viral infection;

- other post-transfusion infection, e.g. malaria;

• 'Near miss' events (this has been introduced more recently). Since 1996, the SHOT scheme has collected data on serious transfusion complications in the UK, from which to make firm recommendations for improvements in transfusion safety. The four UK Blood Services issue approximately 3.5 million blood components each year. Since 1996 there has been a year-on-year increase in the number of reports, with 405 eligible hospitals on the scheme. By the sixth year, participation was running at 93%. The increase in total reports is almost solely the result of an increase in 'incorrect blood component transfused' incidents.

Of 1630 fully analysed reports, the vast majority, i.e. 1045 (64.1%) were 'wrong blood' incidents. Of these, 193 were ABO-incompatible transfusions leading to 11 deaths and 41 cases of major morbidity, for example leading to intensive care unit admission; 92 were RhD incompatible, leading to possible RhD sensitization in females of childbearing potential.

Immune complications constituted 33.1% of reports, with 103 cases of possible TRALI, leading to 11 deaths that were definitely, or probably, related to transfusion, and a further 14 deaths possibly, making TRALI the second largest cause of transfusion-related mortality and morbidity after ABO incompatibility. A large proportion of cases reported as TRALI could not be confirmed in the laboratory.

TTI constituted less than 3% of reports. There were 36 confirmed TTIs of which the majority (22 cases) were of bacterial contamination (19 of platelets, three of red cells), resulting in six deaths.

The SHOT data demonstrate that in high-resource countries, microbiological, and especially virological, safety of the blood supply is advanced. Efforts should now be concentrated in preventing bacterial contamination and in other areas of transfusion medicine, such as the encouragement of appropriate use of blood, safe administration of blood components, accurate patient and sample identification, etc.

In view of the inherent risks of blood transfusion and difficulties with donor recruitment due to escalating stringent donor selection criteria, blood components should only be transfused when the benefits outweigh the risks.

There are several reasons for aiming at reducing unnecessary allogeneic blood transfusion:

1 safety of the patient, by avoiding errors, as well as microbiological and immunological risks;

2 shortages of blood and increasing difficulties in the recruitment of blood donors;

3 cost containment;

4 high anxiety levels in patients that are disproportionate to the real residual risk of transfusion.

There are several alternatives to allogeneic blood transfusion, which can be classified as operational, biological and pharmacological, as listed below.

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