Review of the problems involved in using enzymes in blood group serology--provision of freeze-dried ICSH/ISBT protease enzyme and anti-D reference standards. International Council for Standardization in Haematology. International Society of Blood Transfusion.

Proteolytic enzyme preparations and techniques used routinely in blood group serology for the detection of atypical patient antibodies prior to transfusion vary widely and are often poorly standardised. Recent advances have been made in the use of biochemical methods to standardise and stabilise the potency of the enzyme preparations used. A joint working party of the International Council for Standardization in Haematology (ICSH) and the International Society of Blood Transfusion (ISBT) has investigated possibilities for the provision of standards for the protease preparations and techniques. The specification for these standards was that the performance of enzyme reference preparation in the reference technique should be of equivalent sensitivity to the ICSH/ISBT LISS spin indirect antiglobulin test using a titration series of a reference weak anti-D, and be free from false-positive reactions. The working party circulated materials for evaluation in inter-laboratory trials, followed by a laboratory workshop meeting to achieve agreement on the specification for reference materials and methods. Reference freeze-dried papain at 0.6 azoalbumin units and weak anti-D preparations (91/562) have been prepared and validated to meet these specifications. The performance of a test enzyme preparation in the technique for which it is recommended for use should be at least equal to that of the reference papain preparation, by the reference two-stage technique in terms of sensitivity, using a titration series of the reference anti-D, and freedom from false-positive reactions, using six fresh inert sera. The reference papain and weak anti-D can also be used to calibrate the level of proteolytic activity required in other procedures in blood group serology, such as new technology methods for antibody detection, and automated and microplate cell grouping procedures. These preparations and an agreed method for their use are now available from listed centres as ICSH/ISBT and Food and Drug Administration reference materials.

Screening potential blood donors at risk for human immunodeficiency virus.

Even though all blood donated for transfusion is tested for the presence of human immunodeficiency virus (HIV) antibodies, there exists a period of time after infection by the virus before these antibodies can be detected. Blood donated during this window period is capable of transmitting the virus. Therefore, the blood of persons who are at risk for acquired immune deficiency syndrome (AIDS) should not enter the blood supply. Over a period of 4 months, 6573 potential blood donors who entered fixed and mobile blood collection sites in two cities were exposed to alternative interventions the aim of which was to exclude persons at risk for AIDS. We compared the interventions to one another and to existing materials in terms of the numbers of at-risk persons who did or did not donate for transfusion, the amount of attention paid to the materials, the scores on a comprehension test, and the self-reports by the subjects of attitudes towards the various interventions. At-risk donors who were asked direct AIDS risk behavior questions in addition to the current health history questions were more likely to be screened out than those who underwent alternative health history interviews (p less than 0.01). Potential donors paid more attention to the experimental brochures than to the experimental video or current materials (p less than 0.05). Comprehension scores were better for the new brochure and the video than for the current brochure (p less than 0.05). Donors were not offended by the experimental interventions.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of biosafety principles in blood establishments.

In light of increasing public and employee concern over potential infectious hazards associated with blood and other body fluids, several government agencies (the Food and Drug Administration, the Centers for Disease Control, the Occupational Safety and Health Administration, the Environmental Protection Agency, the Health Care Financing Administration and the National Heart, Lung and Blood Institute) cosponsored a Biosafety Workshop in April 1988. The objective of the workshop was to identify appropriate biosafety practices and standard control procedures to protect workers involved in the collection, storage, and transportation of human blood donations with the least possible disruption of the nation's blood supply. Speakers focused on human immunodeficiency virus (HIV) and hepatitis B virus (HBV); however, the safety principles discussed were considered equally applicable to other known (e.g., non-A, non-B hepatitis and human T-lymphotropic virus type I (HTLV-1) blood-transmitted infections. The resulting consensus included the need for blood establishments to develop and apply thoughtful biosafety programs to address staff training, accident prevention, HBV vaccination, handling spills, managing contaminated waste and transporting blood specimens. There was lack of agreement, however, on the usefulness of gloves during the phlebotomy of healthy blood donors.

Detection of blood group A-like substance in bacterial and viral vaccines by countercurrent immunoelectrophoresis using Helix pomatia lectin.

The technique of countercurrent immunoelectrophoresis (CI), using the N-acetyl glucosamine-binding lectin from Helix pomatia, provided a rapid, sensitive, inexpensive, specific and reliable method for assaying blood group A-like substances in both bacterial and viral vaccines. Blood group A-like substance was detected in the pneumococcal polysaccharide vaccine manufactured by Merck Sharp & Dohme up to 1981 and in a staphylococcus vaccine ( Staphage Lysate) manufactured by Delmont Laboratories. Other US licensed vaccines, including diphtheria and tetanus toxoids, pertussis, meningococcal polysaccharide and influenza vaccines, did not contain detectable amounts of this substance. Human anti-A globulins did not provide a satisfactory reagent for the CI assay because they contained precipitating activities to the vaccine components.

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.