Donor deferral registries.

In the last half of this century, donor deferral registries have grown in size, scope, and importance for blood collection organizations and regulatory agencies. This has occurred despite the lack of direct evidence that, when used with all other methods, they contribute meaningfully to the safety of the blood supply. Any decrease in the perceived benefit of deferral registries has been a result of the introduction of a panoply of serological testing of donor blood intended to detect transmissible disease. As the sensitivity of serological testing improves, the relative merit of the subjective methods used for blood supply safety diminish. Although computers have become a mainstay in the management of deferral registries, accurate and consistent donor identification, good manual systems, and quality control of data bases are key features to their successful management. As with the other subjective methods used in maintaining blood supply safety, techniques must be developed to determine the value of the many features of donor deferral registries. Efforts must be made to simplify these processes and focus on those elements that provide important contributions to blood supply safety. Today, donor deferral registries are major activities in most blood centers and are believed to play a significant role in blood supply safety. It is time for their role to be carefully reexamined.

The significance of the blood-borne viruses: blood banking and transfusion medicine.

Most of the blood-borne infections that have held our attention during the last half of this century have been well characterized. Although HIV and the hepatitis viruses have enormous world-wide public health implications, there has been considerable success in their prevention of transmission by transfusion. The technology is available to treat and eliminate from virtually all non-cellular blood products the transmission of disease caused by those viruses for which we have had the greatest concern. However, for the cellular blood products the basic methods of prevention continue to be imperfect: donor selection and viral serological testing. The significance of the transmission of blood-borne agents by these products depends upon the frequency of the agent in the donor population and the serological screening performed. There is a marked degree of variation in frequency of these infections, dependent upon geography, living conditions, and life style. Data on the frequency of transfusion-transmitted disease are meagre and usually based upon indirect estimates. In the United States the frequency of the transmission of HIV by cellular blood products is estimated to be 1:125,000 products transfused. A similar estimate for the transmission of hepatitis is 1:200 products transfused. For the developing countries, some of which experience the highest rates of hepatitis and HIV infection in their populations, data on the frequency of transfusion transmission are not generally available. In recent years, new evidence has stimulated interest in a few transfusion-transmissible diseases that, although uncommon from the public health perspective, have both real and potential transfusion impacts for the use of plasma and plasma derivatives as well as cellular products.(ABSTRACT TRUNCATED AT 250 WORDS)

Relative prevalence and risk factors of HTLV-I and HTLV-II infection in US blood donors.

The clinical significance of human T-cell lymphotropic virus type II (HTLV-II) infection, unlike that of HTLV-I, is unknown, and the major known association of HTLV-II seropositivity is with intravenous drug abuse. Screening of blood donors for HTLV-I, now routine in North America, does not distinguish this retrovirus from HTLV-II. To find out more about the seroepidemiology of and risk factors for HTLV I and II, blood from 480,000 volunteer donors in five geographically separate US urban centres was tested for antibodies to HTLV-I/II and HIV-1. Confirmed HTLV-I/II seropositive donors were then followed up by DNA amplification to distinguish type I from type II and by interviews focusing on possible risk factors. HTLV seroprevalence was 3.3 times greater than that for HIV-1 (0.043% vs 0.013%). DNA amplification on 65 of the 207 HTLV-I/II seropositive donors revealed that 34 (52%) had HTLV-II infection and 28 (43% had HTLV-I; 3 samples were uninformative. Interviews of 49 donors showed that whereas HTLV-I was principally associated with donor origin from endemic regions, the major risk factor for HTLV-II infection was intravenous drug use. The surprisingly high rate of HTLV-II infection in US blood donors raises important public health and donor counselling issues since HTLV-I infection is associated with adult T-cell leukaemia and a neurological disorder while the pathogenicity of HTLV-II is as yet unclear.

A review of recent events related to surrogate testing of blood to prevent non-A, non-B posttransfusion hepatitis.

A workshop sponsored by the Food and Drug Administration was held recently during which available data were reviewed concerning surrogate testing of blood donated for transfusion in order to reduce the risks of posttransfusion non-A, non-B hepatitis. Clinical studies from which the efficacy of testing for alanine aminotransferase and antibody to hepatitis B core antigen (anti-HBc) could be predicted indicated such testing would be useful, although several studies using tests for anti-HBc developed recently questioned their effectiveness. Different approaches to establishing the cut-off values for the screening tests were presented and difficulties regarding test standardization were discussed. The legal, ethical, and medical implications for donors of surrogate screening programs in the United States also were considered. A meeting sponsored by the private sector that included representatives of the major blood banking organizations and was convened to discuss the workshop proceedings and nationwide screening of the blood supply also is summarized.

Du confirmation.

The need for repeat antiglobulin testing to detect the Du phenotype in donor blood already labeled as Rh-negative was challenged. The confirmatory testing by hospital transfusion services rejected only 47 units in 2.6 million tested. The confirmatory antiglobulin test for Du currently required of hospital transfusion services could be omitted.

Weak D antigen testing using the groupamatic system.

Reliable detection of the weak D (Du) antigen has been a problem for the Groupamatic typing equipment. Using several anti-D sera of known concentration and Du red cells, dose-response curves produced by the Groupamatic revealed variation in the ability to detect the Du antigen by commercial anti-D reagents. Variation in the reactivity of the Du antigen among Du-positive donors was noted. Studies were conducted to determine optimal conditions for the Groupamatic to detect the weakest Du cells. When these conditions were applied to the retesting, 28 cell samples previously found falsely negative by a number of blood centers were accurately detected.

Priapism during filtration leukapheresis.

Priapism has been observed during two out of 3,680 filtration leukapheresis procedures in male donors and has been reported during hemodialysis. Both procedures are associated with enhanced granulocyte adhesion and aggregation presumably due to C5a. During both procedures, heparin is administered and this drug has been shown to cause heparin-dependent anti-platelet antibodies. It is suggested that complement mediated venous leukostasis or immune-induced platelet aggregates might impair the normal blood flow from the penis and result in a state of priapism.

Rapid in vivo destruction of Yt(a+) erythrocytes in a recipient with anti-Yta.

A patient with anti-Cartwright (anti-Yta) is reported. Immunohematologic studies showed this antibody to be an IgG immunoglobulin that does not bind complement. A 51Cr red blood cell survival study resulted in a greatly reduced half-life of less than six hours of Yt(a+) cells. The antibody titer increased threefold after the red blood cell survival study. Determination of red cell survival is indicated when crossmatch-incompatible blood transfusion is considered.

Immunosuppressive therapy of Factor VIII inhibitors.

Immunosuppressive therapy was used in seven hemophiliac and three nonhemophiliac patients with factor VIII inhibiors. Permanent disappearance of the inhibitor occurred in three hemophiliac and two nonhemophiliac patients following treatment with cyclophosphamide and factor VIII. Critical factors influencing the response to therapy may include both the titer and duration of the inhibitor and the degree of intervening factor VIII exposure prior to immunosuppressive therapy. Two severe hemophiliacs with low titer inhibitors that disappeared without specific therapy are also reported.