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Blood bank guidelines for HTVL-III testing: One year's experience
Editorial Blood Bank Guidelines for HTLV-III Testing: One Year's Experience Harold V. Lamberson, Jr., M.D., Ph.D. Director Syracuse Region Blood Services American Red Cross Syracuse, N e w York 13202-3368
Background The first cases of Pneumo~3'stis carinii pneumonia in hemophiliacs were reported in MMWR in July 1982 (2). Those affected had been treated with Factor VIII Concentrate, a plasma derivative manufactured from large pools of plasma consisting of several thousand individual donations. Theoretically, a single plasma donation containing an infectious agent could contaminate an entire plasma pool. Therefore, a single injection of Factor VII1 exposes the recipient to thousands of donors. Retrospectively, it is clear that the initial cases of AIDS in hemophiliacs were a clue that AIDS is caused by a blood-borne transmissible agent. Within 6 months of the first published cases of Pneumocystis pneumonia in hemophiliacs, the initial case report of possible AIDS following the transfusion of single donor blood components appeared (3). One of the initial reports involved transfusion of platelets from a donor who developed clinical AIDS subsequent to the implicated donation. The association of AIDS with the transfusion of single donor blood components further incriminated a blood-borne agent as the cause of AIDS. Accordingly, the blood banking industry and the FDA moved quickly to implement blood donor exclusion criteria in an effort to discourage blood donation by individuals at risk for AIDS. In March 1983, all blood banks voluntarily began providing informational materials to blood donors advising them of the recognized AIDS risk groups and signs and symptoms of
Clinical MicrobiologyNewsletter8:19.1986
AIDS. Potential donors with risk factors or signs and symptoms of AIDS were and continue to be asked not to donate blood. Current AIDS-related instructions for blood donors are summarized in Table 1. Good evidence exists that the voluntary donor exclusion criteria significantly decreased blood donations by individuals at risk for hepatitis B, syphilis, and HTLVIII/LAV infection. Unfortunately, it is also apparent that the voluntary exclusion criteria were not 100% effective in eliminating blood donations by individuals infected with HTLV-III/LAV.
Screening Test Since the discovery of HTLV-II1/ LAV as the etiologic agent of AIDS (1, 6), rapid progress in the development of assays for detecting antibody to HTLV-11I/LAV has been made. The FDA moved quickly to license, and the blood banking industry to implement, serologic testing to identify donors who have been exposed to HTLV-III/LAV. On March 2, 1985, the first manufacturer to distribute test kits for detecting
antibody to HTLV-III for screening blood donors was licensed. Other manufacturers were licensed over the ensuing months. With one exception, currently licensed manufacturers' assays are enzyme-linked immunoassays which use disrupted HTLV-III propagated in H-9 cells as antigen (Abbott, Ortho, DuPont, ElectroNucleonics, Organon Technica, Travenol Genetech). With one exception (Genetic Systems), the antigen is prepared from LAV grown in CEM cells. Manufacturers' claims for the assays range from 95.4-100% sensitivity and 99.2-99.7% specificity. Currently, no recognized standard for establishing the presence of HTLV-III antibody in human blood is available. Consequently, sensitivity is based on the assumption that the prevalence of HTLV-III antibodies in AIDS patients is 100% and specificity on the assumption that the prevalence of HTLV-III antibodies in blood donors is 0%. For each FDA licensed procedure, specimens that have absorbance values above the cutoff point on initial testing
Table 1 Acquired Immune Deficiency Syndrome (AIDS) Information for Blood Donors Persons who are in greatest danger of acquiring and transmitting AIDS and who must not give blood are:
Any male who has had sex with another male since 1977. A person who has ever taken illegal drugs by needle. People from Haiti, Burundi, Kenya, Rwanda, Tanzania, Uganda, and Zaire who came to the United States after 1977. Anyone who has AIDS or one of its signs or symptoms (see below). Any person who has had a positive test for HTLV-III antibody, showing past exposure to the AIDS virus. The sexual partner of any person described above. The sexual partner of any person with hemophilia. Signs and Symptoms of AIDS
Unexplained weight loss. Night sweats. Blue or purple spots on or under the skin. Long-lasting white spots or unusual sores in the mouth. Lumps in the neck, armpits, or groin lasting more than a month. Fever greater than 99 ° for 10 days. Diarrhea lasting more than 1 month. Having these symptoms does not mean you have AIDS. However, it is suggested that you see your doctor. Do not give blood.
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are considered initially to be reactive. All initially reactive specimens are retested in duplicate by the same method. If one or both of the retests are reactive, the specimen is said to be repeatedly reactive and considered to be positive for antibodies to HTLV-111. If, upon retesting, negative results are obtained, the initially reactive specimen is considered to be nonreactive. The number of initially reactive specimens that are found to be repeatedly reactive on retesting represents a measure of the reproducibility of the assays which ranges from 34 to 92%.
Test Policy Current policy requires performing a single determination on a specimen from each blood donation. All initially reactive specimens are retested in duplicate. Repeatedly reactive donations are discarded and donor demographic information is recorded in confidential computerized donor deferral registries to interdict future donations from individuals who are repeatedly reactive on one donation. Only nonreactive blood donations are used for transfusion or manufacturing of derivatives. The continuation of voluntary donor exclusion criteria along with the described serologic screening has greatly improved transfusion safety. A Centers for Disease Control (CDC) report (5) notes that "continued use of this highly sensitive test procedure for HTLV-III antibody, in combination with voluntary avoidance of donation by members of high-risk groups, will virtually eliminate the risk of acquired immunodeficiency syndrome (AIDS) transmission by the nation's blood supply." Additionally, manufacturing procedures for the preparation of Factor VIII now include a heat treatment that has been shown to effectively inactivate HTLVIII/LAV. Consequently, the risk of transmitting HTLV-III/LAV by Factor VIII concentrate is also thought to be greatly reduced.
Transfusion Safety and Confidentiality Blood centers have obligations to donors as well as to recipients. While the above-described policies have been developed to protect the recipient, they
148
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+ 02.20
do not address responsibilities to the donor. Additional policies have been implemented to address donor-related issues. A major concern is that a screening test with a specificity of 99.5% will falsely identify many individuals as positive when applied to a low prevalence population. For example, assume that of 10,000 blood donors, five have been exposed to HTLV-III/LAV. If the sensitivity of the assay is 100%, all five will be correctly identified as positive by the screening test. However, an additional 45 donors would be positive in the screening test and represent 45 false positives. Most agree that it would be inappropriate and unethical to advise such individuals that they may have been exposed to the virus that causes AIDS. Fortunately, although there is no currently licensed confirmatory test for antibody to HTLV-III, available data support the use of the Western Blot method (an immunoprecipitation technique that detects antibody to specific viral proteins) to "confirm" the positivity of specimens repeatedly reactive by ELISA. Of the first 800,000 donors tested in the Red Cross Blood Centers, 1% were initially reactive, 0.17% (17/10,000) repeatedly reactive, and 0.037% (3.7/10,000) Western Blot positive. While the prevalence of repeatedly reactive donors was similar among male and female donors, Western Blot positive donors were predominately male (92%). Approximately 93% of AIDS cases reported to the CDC have been males. Furthermore, there was a striking correlation between the prevalence of Western Blot positivity in a donor population and the number of AIDS cases reported to the CDC for the same geographic area. These observations, in part, are the basis for current policies concerning donor notification of test results, i.e., to notify only donors who are repeatedly reactive on ELISA and reactive on Western Blot testing. Donors with these findings are notified and provided with the Public Health Services recommendations for persons who have a positive HTLV-II1 antibody test (4). Information for donors notes that: 1) currently available tests detect antibody
:c 1086 ELsevier Science Publishing Co.. Inc.
and do not detect the virus; 2) currently licensed tests are not diagnostic tests for AIDS; 3) the natural history ol HTLV-IlI/LAV infection in otherwise healthy individuals is currently largely unknown; 4) until information to the contrary is available, it is best to assume that individuals who are Western Blot positive have been exposed to HTLV-III and may be contagious; and 5) specific recommendations to prevent spreading of the virus are provided (see Table 2). Because of the extraordinary potential for misuse of HTLV-III/LAV test results, blood banks have developed elaborate procedures to ensure confidentiality of test results. Only with written consent from the donor are test results provided to anyone other than the donor. Thus, blood banks operate with two sets of standards related to HTLV-III/LAV testing. One set of standards is designed to protect the recipient (donor exclusion criteria and interdiction of repeatedly reactive donations); the other to protect the donor (confirmatory Western Blot testing, strict confidentiality, and donor counseling).
Current Problems and Needs It is widely believed that current policies and procedures have significantly enhanced transfusion safety. However, several areas for concern and further development remain. Among the concerns that wilt continue to attract the attention of virologists and blood bankers are: 1. All currently available licensed assays detect antibody to HTLV-II1/ LAV. While the sensitivity of these assays is at least equivalent to any other routine serologic procedure, concern remains that antibody assays may not detect the earliest stages of infection. It is for this reason that voluntary donor exlusion criteria must remain in effect. 2. As noted above, the specificity of currently licensed assays also compares very favorably to other routine serologic procedures. When applied to a population with an extremely low prevalence of infection, however, the majority of screening
('linical Microbiolog) Newsletter 8:19,1986
reactive and, by present policies, be permanently excluded from further donation. For the past 4 months, approximately 0.015% or 1.5/10,000 donors have been Western Blot positive, representing only 1200 donors/yr. If the sensitivity of Western Blot testing permits the identification of all true positive donors, then current policies based on a repeatedly reactive ELISA may result in the unnecessary exclusion of approximately 38,800 blood donors/yr. Ongoing erosion of the donor base will eventually jeopardize the adequacy of the blood supply. An inadequate blood supply is an unsafe blood supply. Consequently, assays and procedures must be developed to identify only those donors whose blood is unsafe for transfusion.
Table 2 R e c o m m e n d a t i o n s for the I n d i v i d u a l
1. The prognosis for an individual infected with HTLV-III over the long term is not known. However, data available from studies conducted among homosexual men indicate that most persons will remain infected. 2. Although asymptomatic, these individuals may transmit HTLV-Ill to others. Regular medical evaluation and follow-up is advised, especially for individuals who develop signs or symptoms suggestive of AIDS. 3. Refrain from donating blood, plasma, body organs, other tissue, or sperm. 4. There is a risk of infecting others by sexual intercourse, sharing of needles, and possibly, exposure of others to saliva through oral-genital contact or intimate kissing. The efficacy of condoms in preventing infection with HTLV-III is unproven, but the consistent use of them may reduce transmission. 5. Toothbrushes, razors, or other implements that could become contaminated with blood should not be shared. 6. Women with a seropositive test, or women whose sexual partner is seropositive, are themselves at increased risk of acquiring AIDS. If they become pregnant, their offspring are also at increased risk of acquiring AIDS. 7. After accidents resulting in bleeding, contaminated surfaces should be cleaned with household bleach freshly diluted 1:10 in water. 8. Devices that have punctured the skin, such as hypodermic and acupuncture needles, should be steam sterilized by autoclave before reuse or safely discarded. Whenever possible, disposable needles and equipment should be used.
References 1. Barre-Sinoussi, F. et al. 1983. Isola-
9. When seeking medical or dental care for intercurrent illness, these pesons should inform those responsible for their care of their positive antibody status so that appropriate evaluation can be undertaken and precautions taken to prevent transmission to others. 10. Testing for HTLV-III antibody should be offered to persons who may have been infected as a result of their contact with seropositive individuals (e.g., sexual partners, persons with whom needles have been shared, infants born to seropositive mothers).
2.
3.
test positive donors will be false positives. Western Blot procedures are labor intensive, lengthy, expensive, and not fully standardized. As such, these assays are not readily adaptable to a large production blood center setting, therefore, alternative "confirmatory" test methods are needed. One approach is the development of antibody assays using genetically engineered viral protein antigens. Other approaches would be assays to detect viral antigen or the viral genome. . Confirmatory tests are needed not only for donor counseling but also to prevent the unnecessary exclusion
Clinical Microbiology Newsletter 8:19,1986
of healthy donors. Because there is currently no licensed or generally accepted " g o l d standard" for confirmatory testing to determine which of repeatedly reactive donors are true positives, many ELISA false positive donors are being excluded from the blood donor base. Approximately 12,000,000 whole blood donations are given annually in the United States. Since the average whole blood donor donates approximately 1.5 times/yr, this figure represents about 8,000,000 donors. Assuming a repeatedly reactive rate of 0.5%, approximately 40,000 donors/yr will be repeatedly
© 1986 Elsevier Science Publishing Co., Inc.
4.
5.
6.
tion of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS). Science 220:868-871. Centers for Disease Control. 1982. Pneumocystis carinii pneumonia among persons with hemophilia A. MMWR 31:365-367. Centers for Disease Control. 1982. Possible transfusion-associated acquired immune deficiency syndrome (AIDS)--California. MMWR 31:652654. Centers for Disease Control. 1985. Provisional Public Health Service Inter-Agency recommendations for screening donated blood and plasma for antibody to the virus causing acquired immunodeficiency syndrome. MMWR 34:1 - 5. Centers for Disease Control. 1985. CDC Update: Public Health Services Workshop on human T-lymphotropic virus type Ill antibody testing--United States. MMWR 34:477-478. Gallo, R. O. et al. 1984. Frequent detection and isolation of cytopathic retroviruses (HTLV-III) from patients with AIDS and at risk for AIDS. Science 224:500-503.
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Background The first cases of Pneumo~3'stis carinii pneumonia in hemophiliacs were reported in MMWR in July 1982 (2). Those affected had been treated with Factor VIII Concentrate, a plasma derivative manufactured from large pools of plasma consisting of several thousand individual donations. Theoretically, a single plasma donation containing an infectious agent could contaminate an entire plasma pool. Therefore, a single injection of Factor VII1 exposes the recipient to thousands of donors. Retrospectively, it is clear that the initial cases of AIDS in hemophiliacs were a clue that AIDS is caused by a blood-borne transmissible agent. Within 6 months of the first published cases of Pneumocystis pneumonia in hemophiliacs, the initial case report of possible AIDS following the transfusion of single donor blood components appeared (3). One of the initial reports involved transfusion of platelets from a donor who developed clinical AIDS subsequent to the implicated donation. The association of AIDS with the transfusion of single donor blood components further incriminated a blood-borne agent as the cause of AIDS. Accordingly, the blood banking industry and the FDA moved quickly to implement blood donor exclusion criteria in an effort to discourage blood donation by individuals at risk for AIDS. In March 1983, all blood banks voluntarily began providing informational materials to blood donors advising them of the recognized AIDS risk groups and signs and symptoms of
Clinical MicrobiologyNewsletter8:19.1986
AIDS. Potential donors with risk factors or signs and symptoms of AIDS were and continue to be asked not to donate blood. Current AIDS-related instructions for blood donors are summarized in Table 1. Good evidence exists that the voluntary donor exclusion criteria significantly decreased blood donations by individuals at risk for hepatitis B, syphilis, and HTLVIII/LAV infection. Unfortunately, it is also apparent that the voluntary exclusion criteria were not 100% effective in eliminating blood donations by individuals infected with HTLV-III/LAV.
Screening Test Since the discovery of HTLV-II1/ LAV as the etiologic agent of AIDS (1, 6), rapid progress in the development of assays for detecting antibody to HTLV-11I/LAV has been made. The FDA moved quickly to license, and the blood banking industry to implement, serologic testing to identify donors who have been exposed to HTLV-III/LAV. On March 2, 1985, the first manufacturer to distribute test kits for detecting
antibody to HTLV-III for screening blood donors was licensed. Other manufacturers were licensed over the ensuing months. With one exception, currently licensed manufacturers' assays are enzyme-linked immunoassays which use disrupted HTLV-III propagated in H-9 cells as antigen (Abbott, Ortho, DuPont, ElectroNucleonics, Organon Technica, Travenol Genetech). With one exception (Genetic Systems), the antigen is prepared from LAV grown in CEM cells. Manufacturers' claims for the assays range from 95.4-100% sensitivity and 99.2-99.7% specificity. Currently, no recognized standard for establishing the presence of HTLV-III antibody in human blood is available. Consequently, sensitivity is based on the assumption that the prevalence of HTLV-III antibodies in AIDS patients is 100% and specificity on the assumption that the prevalence of HTLV-III antibodies in blood donors is 0%. For each FDA licensed procedure, specimens that have absorbance values above the cutoff point on initial testing
Table 1 Acquired Immune Deficiency Syndrome (AIDS) Information for Blood Donors Persons who are in greatest danger of acquiring and transmitting AIDS and who must not give blood are:
Any male who has had sex with another male since 1977. A person who has ever taken illegal drugs by needle. People from Haiti, Burundi, Kenya, Rwanda, Tanzania, Uganda, and Zaire who came to the United States after 1977. Anyone who has AIDS or one of its signs or symptoms (see below). Any person who has had a positive test for HTLV-III antibody, showing past exposure to the AIDS virus. The sexual partner of any person described above. The sexual partner of any person with hemophilia. Signs and Symptoms of AIDS
Unexplained weight loss. Night sweats. Blue or purple spots on or under the skin. Long-lasting white spots or unusual sores in the mouth. Lumps in the neck, armpits, or groin lasting more than a month. Fever greater than 99 ° for 10 days. Diarrhea lasting more than 1 month. Having these symptoms does not mean you have AIDS. However, it is suggested that you see your doctor. Do not give blood.
© 1986ElsevierSciencePublishingCo.. Inc.
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are considered initially to be reactive. All initially reactive specimens are retested in duplicate by the same method. If one or both of the retests are reactive, the specimen is said to be repeatedly reactive and considered to be positive for antibodies to HTLV-111. If, upon retesting, negative results are obtained, the initially reactive specimen is considered to be nonreactive. The number of initially reactive specimens that are found to be repeatedly reactive on retesting represents a measure of the reproducibility of the assays which ranges from 34 to 92%.
Test Policy Current policy requires performing a single determination on a specimen from each blood donation. All initially reactive specimens are retested in duplicate. Repeatedly reactive donations are discarded and donor demographic information is recorded in confidential computerized donor deferral registries to interdict future donations from individuals who are repeatedly reactive on one donation. Only nonreactive blood donations are used for transfusion or manufacturing of derivatives. The continuation of voluntary donor exclusion criteria along with the described serologic screening has greatly improved transfusion safety. A Centers for Disease Control (CDC) report (5) notes that "continued use of this highly sensitive test procedure for HTLV-III antibody, in combination with voluntary avoidance of donation by members of high-risk groups, will virtually eliminate the risk of acquired immunodeficiency syndrome (AIDS) transmission by the nation's blood supply." Additionally, manufacturing procedures for the preparation of Factor VIII now include a heat treatment that has been shown to effectively inactivate HTLVIII/LAV. Consequently, the risk of transmitting HTLV-III/LAV by Factor VIII concentrate is also thought to be greatly reduced.
Transfusion Safety and Confidentiality Blood centers have obligations to donors as well as to recipients. While the above-described policies have been developed to protect the recipient, they
148
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+ 02.20
do not address responsibilities to the donor. Additional policies have been implemented to address donor-related issues. A major concern is that a screening test with a specificity of 99.5% will falsely identify many individuals as positive when applied to a low prevalence population. For example, assume that of 10,000 blood donors, five have been exposed to HTLV-III/LAV. If the sensitivity of the assay is 100%, all five will be correctly identified as positive by the screening test. However, an additional 45 donors would be positive in the screening test and represent 45 false positives. Most agree that it would be inappropriate and unethical to advise such individuals that they may have been exposed to the virus that causes AIDS. Fortunately, although there is no currently licensed confirmatory test for antibody to HTLV-III, available data support the use of the Western Blot method (an immunoprecipitation technique that detects antibody to specific viral proteins) to "confirm" the positivity of specimens repeatedly reactive by ELISA. Of the first 800,000 donors tested in the Red Cross Blood Centers, 1% were initially reactive, 0.17% (17/10,000) repeatedly reactive, and 0.037% (3.7/10,000) Western Blot positive. While the prevalence of repeatedly reactive donors was similar among male and female donors, Western Blot positive donors were predominately male (92%). Approximately 93% of AIDS cases reported to the CDC have been males. Furthermore, there was a striking correlation between the prevalence of Western Blot positivity in a donor population and the number of AIDS cases reported to the CDC for the same geographic area. These observations, in part, are the basis for current policies concerning donor notification of test results, i.e., to notify only donors who are repeatedly reactive on ELISA and reactive on Western Blot testing. Donors with these findings are notified and provided with the Public Health Services recommendations for persons who have a positive HTLV-II1 antibody test (4). Information for donors notes that: 1) currently available tests detect antibody
:c 1086 ELsevier Science Publishing Co.. Inc.
and do not detect the virus; 2) currently licensed tests are not diagnostic tests for AIDS; 3) the natural history ol HTLV-IlI/LAV infection in otherwise healthy individuals is currently largely unknown; 4) until information to the contrary is available, it is best to assume that individuals who are Western Blot positive have been exposed to HTLV-III and may be contagious; and 5) specific recommendations to prevent spreading of the virus are provided (see Table 2). Because of the extraordinary potential for misuse of HTLV-III/LAV test results, blood banks have developed elaborate procedures to ensure confidentiality of test results. Only with written consent from the donor are test results provided to anyone other than the donor. Thus, blood banks operate with two sets of standards related to HTLV-III/LAV testing. One set of standards is designed to protect the recipient (donor exclusion criteria and interdiction of repeatedly reactive donations); the other to protect the donor (confirmatory Western Blot testing, strict confidentiality, and donor counseling).
Current Problems and Needs It is widely believed that current policies and procedures have significantly enhanced transfusion safety. However, several areas for concern and further development remain. Among the concerns that wilt continue to attract the attention of virologists and blood bankers are: 1. All currently available licensed assays detect antibody to HTLV-II1/ LAV. While the sensitivity of these assays is at least equivalent to any other routine serologic procedure, concern remains that antibody assays may not detect the earliest stages of infection. It is for this reason that voluntary donor exlusion criteria must remain in effect. 2. As noted above, the specificity of currently licensed assays also compares very favorably to other routine serologic procedures. When applied to a population with an extremely low prevalence of infection, however, the majority of screening
('linical Microbiolog) Newsletter 8:19,1986
reactive and, by present policies, be permanently excluded from further donation. For the past 4 months, approximately 0.015% or 1.5/10,000 donors have been Western Blot positive, representing only 1200 donors/yr. If the sensitivity of Western Blot testing permits the identification of all true positive donors, then current policies based on a repeatedly reactive ELISA may result in the unnecessary exclusion of approximately 38,800 blood donors/yr. Ongoing erosion of the donor base will eventually jeopardize the adequacy of the blood supply. An inadequate blood supply is an unsafe blood supply. Consequently, assays and procedures must be developed to identify only those donors whose blood is unsafe for transfusion.
Table 2 R e c o m m e n d a t i o n s for the I n d i v i d u a l
1. The prognosis for an individual infected with HTLV-III over the long term is not known. However, data available from studies conducted among homosexual men indicate that most persons will remain infected. 2. Although asymptomatic, these individuals may transmit HTLV-Ill to others. Regular medical evaluation and follow-up is advised, especially for individuals who develop signs or symptoms suggestive of AIDS. 3. Refrain from donating blood, plasma, body organs, other tissue, or sperm. 4. There is a risk of infecting others by sexual intercourse, sharing of needles, and possibly, exposure of others to saliva through oral-genital contact or intimate kissing. The efficacy of condoms in preventing infection with HTLV-III is unproven, but the consistent use of them may reduce transmission. 5. Toothbrushes, razors, or other implements that could become contaminated with blood should not be shared. 6. Women with a seropositive test, or women whose sexual partner is seropositive, are themselves at increased risk of acquiring AIDS. If they become pregnant, their offspring are also at increased risk of acquiring AIDS. 7. After accidents resulting in bleeding, contaminated surfaces should be cleaned with household bleach freshly diluted 1:10 in water. 8. Devices that have punctured the skin, such as hypodermic and acupuncture needles, should be steam sterilized by autoclave before reuse or safely discarded. Whenever possible, disposable needles and equipment should be used.
References 1. Barre-Sinoussi, F. et al. 1983. Isola-
9. When seeking medical or dental care for intercurrent illness, these pesons should inform those responsible for their care of their positive antibody status so that appropriate evaluation can be undertaken and precautions taken to prevent transmission to others. 10. Testing for HTLV-III antibody should be offered to persons who may have been infected as a result of their contact with seropositive individuals (e.g., sexual partners, persons with whom needles have been shared, infants born to seropositive mothers).
2.
3.
test positive donors will be false positives. Western Blot procedures are labor intensive, lengthy, expensive, and not fully standardized. As such, these assays are not readily adaptable to a large production blood center setting, therefore, alternative "confirmatory" test methods are needed. One approach is the development of antibody assays using genetically engineered viral protein antigens. Other approaches would be assays to detect viral antigen or the viral genome. . Confirmatory tests are needed not only for donor counseling but also to prevent the unnecessary exclusion
Clinical Microbiology Newsletter 8:19,1986
of healthy donors. Because there is currently no licensed or generally accepted " g o l d standard" for confirmatory testing to determine which of repeatedly reactive donors are true positives, many ELISA false positive donors are being excluded from the blood donor base. Approximately 12,000,000 whole blood donations are given annually in the United States. Since the average whole blood donor donates approximately 1.5 times/yr, this figure represents about 8,000,000 donors. Assuming a repeatedly reactive rate of 0.5%, approximately 40,000 donors/yr will be repeatedly
© 1986 Elsevier Science Publishing Co., Inc.
4.
5.
6.
tion of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS). Science 220:868-871. Centers for Disease Control. 1982. Pneumocystis carinii pneumonia among persons with hemophilia A. MMWR 31:365-367. Centers for Disease Control. 1982. Possible transfusion-associated acquired immune deficiency syndrome (AIDS)--California. MMWR 31:652654. Centers for Disease Control. 1985. Provisional Public Health Service Inter-Agency recommendations for screening donated blood and plasma for antibody to the virus causing acquired immunodeficiency syndrome. MMWR 34:1 - 5. Centers for Disease Control. 1985. CDC Update: Public Health Services Workshop on human T-lymphotropic virus type Ill antibody testing--United States. MMWR 34:477-478. Gallo, R. O. et al. 1984. Frequent detection and isolation of cytopathic retroviruses (HTLV-III) from patients with AIDS and at risk for AIDS. Science 224:500-503.
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149