Prevention of transfusion transmitted infections : donor screening and characteristics of recipient populations

Abstract

Minimising the risk for transfusion transmitted infections (TTIs) relies on selection of safe donors, including microbiological screening, and avoidance of unnecessary transfusions.

Blood donor screening for HTLV-I and II, was introduced in Sweden in 1994. The first year six HTLV-I and no HTLV-II positive donors were found, which meant a prevalence of 2 per 100 000. The transmission rate at transfusion is estimated at 15% but only five percent of infected individuals will develop serious disease during their lifetime: tropical spastic paraparesis (TSP) after three to four years or adult T-cell lymphoma (ATL) after several decades. TTIs should be prevented but cost effectiveness needs to be considered.

We estimated the cost for prevention of one death, due to transfusion transmitted HTLV disease (ATL), to $540 million when every donation was tested and $36 million when only new donors were tested. The number of prevented deaths would be almost the same (1/180 versus 1/2 10 years). As a result of this study only new donors are now tested in Sweden.

The age and expected survival of blood transfusion recipients will affect the expected damage caused by transmitted infections, i. e. the development of clinical disease and the risk for secondary spread to infants and sex partners. Survival rates of transfusion recipients in Stockholm and Örebro counties in 1993 were found to be 66% after one year, 51% after 40 months and 39% after seven years for those in Örebro. The median age of recipients was 70 years and 21 % were 80 years or older.

Adequate indications for transfusion are essential. Donated blood is a limited resource and a small risk of infection will always remain, in spite of rigorous safety. Among patients transfused in Örebro County in 1993 and 2000 survival rates were higher in operated patients, in younger patients and in females. Lower survival rates were seen in patients with cancer and in those receiving more than ten units. Overall one year survival rate in 2000 was higher than in 1993 despite higher age among recipients.

Many donors are deferred temporarily or permanently because of false-reactive test results. A survey was performed in 19 blood centres in 11 counties. The viral screening tests showed between 0.01 and 0.2% false-reactive results and the variation for each test was about tenfold. There was also a great variation in deferral rates between counties. In a questionnaire study only 37% of deferred donors found the information at notification sufficient and over 80% were worried by their test result.

There is need for a more standardised approach to the microbiological screening of donors, with the aim to minimise the number of false-reactive results, and need for better information and support to deferred donors.