Screening for human T cell leukaemia/lymphoma virus among blood donors in Sweden: cost effectiveness analysis

British Medical Journal, May 9, 1998 by Elsa Tynell, Soren Andersson, Eva Lithander, Malin Arneborn, Jonas Blomberg, Hans Bertil Hansson, Aud Krook, Mats Nomberg, Kristina Ramstedt, Agneta Shanwell, Anders Bjorkman

Results

Blood donations and transfusions

About 235 000 people donated blood or plasma during 1994; this total included about 34 000 new donors. Blood donors provide an average of 1.88 donations each year for 10 years. During 1994 they donated 444 000 units of whole blood and 209 000 kg of plasma for fractionation; these donations accounted for 522 000 transfusions of erythrocyte concentrates, platelet concentrates, and plasma units. One donation was equivalent to 1.18 transfusions. The data from the pilot study in South Hospital were in accordance with the overall profile in Sweden (one donation was equivalent to 1.23 transfusions).

Recipients of transfusions

The 255 patients who had received transfusions in the pilot study in the Stockholm area had a median age of 70 years; 34 (13%) were younger than 40. The patients received from 1 to 15 units (mean 2.5) during the month of the study. A total of 492 (78%) out of 635 units transfused were erythrocyte concentrates, 21 (3%) were platelets, and 122 (19%) were plasma. The survival rate of all patients who received transfusions was 67% (172/255) at 1 year and 49% (125/255) at 3 years. One out of 10 patients was both younger than 40 and survived for at least 3 years and we therefore assumed that they had a possible life expectancy of more than 30 years.

Screening programme

A total of 648 497 donations were screened for the virus; 1625 (0.25%) samples tested positive by enzyme linked immunosorbent assay. Six donors were confirmed as positive by western blotting; all had the type I profile. Five of these donors were confirmed positive by polymerase chain reaction. About half of the samples that initially tested positive had indeterminate profiles when tested by western blotting. In a subset of 571 samples that repeatedly tested positive by enzyme linked immunosorbent assay 280 (49%) were classed as indeterminate when western blotting was used. All of the 272 indeterminate samples later tested by polymerase chain reaction were negative. No donor was infected with type II virus.

One donor who tested positive had been detected during the pilot study; thus, seven potential donors (two men and five women) tested positive for the virus. The prevalence of infection with the virus among blood donors in Sweden was therefore 2/100 000. Three of the infected donors were of Swedish origin and had no risk factors that would have led to their exclusion from blood donation before testing. The remaining four were originally from Denmark, the United Kingdom, Iran, and Chile. The calculated prevalence for donors born in Europe was 1.3/100 000 and for donors born in Sweden 1/100 000.

Retrospective study

In total 95 patients were identified as having received blood components from the seven donors who tested positive. A total of 41 (43%) recipients were alive and 35 were available for testing. Three of them tested positive (table 1).

Table 1 Test results of patients who received transfusions from donors who tested positive for human T cell leukaemia/lymphoma virus in Sweden