Transfusion Transmitted Injuries Surveillance System
Project Progress Report 2001-2002

4. Discussion

Reporting transfusion reactions in a standardized manner throughout four provinces and more than 50 hospitals proved to be quite a challenge. Developing a set of standardized definitions for transfusion reactions and a set of data to transfer to Health Canada that was agreeable to all parties involved was a process that lasted 18 months. As well, the reporting tools (forms and database) went through several drafts. Since reporting started, in a period of 15 months, 99 serious adverse transfusion reactions were reported to Health Canada by the 56 hospitals participating in the ttiss in the four pilot provinces.

These data should not be considered as national figures and caution must be used in interpreting them. This is a new surveillance system and very few Canadian hospitals participated. In addition, there was no certainty regarding the true level of standardization achieved. There was very little information transferred to Health Canada to interpret the diagnoses and accept cases as valid. In many instances there were no signs or symptoms provided and no laboratory results as well as no text description of the event. This situation has been improved and, for future transfers, data on symptoms, signs and laboratory results will be provided and an agreement is anticipated for the transfer of a narrative description of a reaction. This will ensure a better classification at the national level.

Within the ttiss project, the only reactions being reported to Health Canada are severe reactions. This, in conjunction with the fact that only a small fraction of Canadian hospitals participated during the pilot project, explains the small number collected by the ttiss.

Other surveillance programs such as the Canadian Adverse Drug Reaction Program which collects information on all adverse events to fractionated blood products may have a higher number of reports, but the quality of the ttiss reports is expected to be better as each case has been investigated and validated at the provincial level. It is not possible to evaluate the extent of underreporting since a clinical condition must be recognized first at the primary level as a transfusion reaction within a hospital and some of the reactions were possibly missed.

The absence of denominators from all provinces on the number of blood recipients and on products transfused in the participating hospitals prevented the calculation of rates of adverse transfusion reactions. These data are essential for a surveillance system and should certainly be included for future transfers in order to enable the estimation of risks of adverse reactions.

There were two deaths definitely associated with transfusions that were reported, including one case of acute hemolytic reaction, secondary to a human error, the transfusion of a wrong ABO red cell unit, and one of bacterial contamination. It is difficult to definitely relate the other deaths to transfusion. However, the death associated to the TRALI case is most probably related to transfusion.

Of the adverse events reported, only five were related to fractionated products. Caution is needed with respect to the data on fractionated products. There was no agreement on what reactions should be reported with respect to this type of product and reporting varied significantly from one province to the other. It can be assumed that there was significant underreporting of adverse events related to fractionated products during the reporting period.

ttiss has shown that it can work in pilot settings despite the difficulties inherent in a national surveillance system. It should now expand beyond the pilot provinces and hospitals and, in fact, as of March 2003, almost all provinces and territories have agreed to participate in the ttiss, and the surveillance system will gradually be deployed in Canadian hospitals over the next two years.

ttiss has its limitations in the capacity to capture transmission of viral infections because of the current inability to link with public health data. Such a link is necessary as these infections are often not recognized until weeks or months later when the patient is no longer in hospital. Treating physicians in the community will then notify public health authorities of these cases but only for those infections that are reportable. A pilot project is being planned to look at how this could be done.

Finally, ttiss should expand in the future to include surveillance of major errors in transfusion medicine. There is, currently, an initiative to develop and pilot a system for error surveillance that would eventually be incorporated into ttiss so that the national surveillance system would be more comprehensive.

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