TRANSFUSION Volume 32
July/August 1992
Number 6
Editorials
Human immunodeficiency virus (H1V)-indeterminate Western blots and latent HIV infection derived from infected cell lines eliminates the reactivity in many of these sample^.^.^ However, despite the use of peptides or recombinant antigens, a significant proportion of these sera continue to show reactivity, which suggests either the presence of antibody to HIV-1, crossreactivity to other viral antigens, or perhaps antibody to the vector (e.g., Escherichiu coli) used to make the recombinant antigen.15J6 Western blot testing of serial samples from persons with true seroconversion reveals that reactivity to p24 is almost always associated with early HIV-1 seroconversion." Therefore, the use of blood from donors with reactivity to the p24 band is especially worrisome, although it should be noted that 10 recipients of blood components from six donors with persistent HIV-1 p24 reactivity showed no evidence of HIV-1 seroconversion by Western blot assay.18 To make matters more confusing, there have been studies reporting the presence of HIV-1 infection in a large percentage of high-risk antibody-negative individual^.'^*^^ For example, Imagawa et aI.l9 reported they were able to culture HIV-1 from the blood of 31 (23%) of 133 seronegative homosexual men, 27 of whom have remained seronegative for up to 36 months after the positive culture. Likewise, Hewlett et al.20 reported that they were able to detect HIV-1 DNA sequences by the polymerase chain reaction (PCR)in the blood of 11(41%) of 27 seronegative sexual partners of HIV1-infected hemophiliacs. HIV-1 transmission from the transfusion of seronegative blood has been documented,22 but these studies suggest that the potential for this to occur may be greater than is currently appreciated. Reports of prolonged seroconversion periods have further heightened anxiety levels. Wolinsky et al.23 tested blood specimens collected from 24 homosexual men at 6-month visits prior to seroconversion. Thirteen of these 24 men had indeterminate Western blots at some point
Licensed enzyme immunoassays (EIAs) are most commonly used for testing the blood of individuals for antibody to human immunodeficiency virus type 1 (HIV-l).l If the patient sample is repeatably reactive by EIA, then the Western blot assay is most often performed to verify the presence of HIV-1 antibody.2 This assay typically reveals six to nine characteristic bands if antibodies to HIV-1 proteins of different molecularweights are p r e ~ e n t .Approximately ~ 99.7 percent of volunteer blood donors at low risk for HIV-1 infection will be negative for HIV-1 antibody by the EIA screening test.4 Of the 0.3 percent who have repeatably reactive samples, 80 percent are Western blot n e g a t i ~ e .However, ~ approximately 20 percent of these persons have one or two bands characteristic of HIV-1 on Western blotting. The reactivity usually is to only one or more of the HIV1 core proteins (p17, p24, and p55) and therefore does not meet the definition of a positive specimen (any two of the following bands present: p24, gp41, and either gp120 or gp160) or a negative specimen (no bands present).5 Such specimens are therefore labeled indeterminate, for lack of a better term. Seroconversion rates of 1 to 5 percent in blood donors who are indeterminate by Western blot have been documented, with the majority of these donors seroconvertingover a period of less than 6 months.69 However, most blood donors with indeterminate Western blots remain persistently indeterminate for years and do not ser~convert.~J~ Thus counseling of donors is difficult, and confidence in the safety of the blood supply is diminished. The cause of most of these atypical Western blot patterns is poorly understood. Atypical Western blot patterns have been associated with heat-related inactivation of serum samples,11J2 in vitro hem~lysis,'~ eleyated bilirubin levels,13 rheumatoid factor,13 polyclonaI gammopathy,13 systemic lupus erythematosus,13 and antibodies to DR human lymphocyte antigens.14 The use of recombinant HIV-1 antigens or peptides instead of viral lysate
497
498
EDITORIAL.
TRANSFUSION
Vol. 32. No. 6-1992
ual practices, and so on. However, I think the differprior to a diagnostic Western blot. HIV-1 DNA was detected by PCR in 20 of the 24 men prior to seroconences are more likely explained by the possibility of version: at 42 months before seroconversion in 2 men; false-positive culture and/or PCR results. In the original study of Imagawa et al.,19 positive at 36 months in 1 man; at 30 months in 1 man; at 24 months in 4 men; at 18 months in 8 men; at 12 months culture results in most of the antibody-negative individuals were not confirmed by PCR or seroconversion. in 1 man; and at 6 months in 3 men. Moreover, this group recently reported32that, in a folThe above studies are disturbing because they suggest low-up study culturing 151 blood samples from 27 anthat the number of Western blot-indeterminateand -seronegative donors who are infected with HIV-1 is greater tibody-negative men who were culture positive in the original study, virus could be isolated from only one than we think. These studies also raise concerns regarding the performance of our serologic screening and conman. Apparently, none of these men had seroconverted. In addition, virus was isolated from only 3 (1.3%) of firmatory assays in detecting HIV-1 infection. Therefore, 230 other antibody-negative men who were continuing it is reassuring Eble et al.24 report, in this issue of to have anal intercourse with more than one person. InTRANSFUSION, that, when they used sensitive PCR complete infection could explain these results, but conand viral culture techniques no HIV-1 infection was detamination or specimen mix-up must be strongly tected in 65 follow-up samples from 26 blood donors considered. with persistently indeterminate Western blots for 1 to 3 Likewise, in the study of Hewlett et al.,zo positive years. At least 60 percent of these donors had at least a PCR resulfs in seronegative women were not confirmed p24 band on Western blot. In addition, HIV-1 infection by viral isolation. Moreover, the extreme sensitivity of was not detected in the blood of 16 persistently seroPCR and the consequent high risk of obtaining false negative heterosexual partners of infected transfusion repositives with PCR, due to carryover from previously cipients nor in the blood of 6 seronegative homosexual amplified material, is well known.33 Almost all laboramen at high risk. In contrast, HIV-1 was detected in all tories with experience in PCR detection have had prob21 antibody-positive individuals tested. lems with false-positive results at one time or another. This report is consistent with at least 10 other studies These false positives may easily be missed unless an that also found no evidence of HIV-1 infection in testing adequate number of negative controls and blinded samthe blood of at least 300 donors who were persistently ples are processed and assayed simultaneouslywith study indeterminate by Western blot and of more than 500 specimens. Blinded samples should not be decoded until high-risk seronegative individuals by PCR and/or viral isolation m e t h ~ d ~ . ~ ~ ~ ~ ~ ~ ~ ~ after ~ ~interpretation ~ ~ - ~of ~results. In contrast, a number of studies, such as the one by How does one explain such diverse findings? The popEble et al. in this issue of TRANSFUSION, have not ulations tested in the different studies may explain some been able to detect HIV-1 infection in high-risk seroof the differences. For example, the likelihood of denegative individuals when the combined application of tecting HIV-1 infection in homosexual men with persistently indeterminate Western blots will be much higher viral culture and PCR have been used. These data are reassuring and support the recent Food and Drug Adminthan that in blood donors at low risk for HIV-1 infection, istration recommendation to change the deferral period because the prevalence of HIV-1 infection is signififor sexual partners of persons with high-risk behavior cantly higher. The study by Eble et al.,” together with from lifetime to 12 months.34 similar studies, only indicates that the presence of However, because it is likely that individuals are more HIV-1 infection in low-risk blood donors with persistlikely to be HIV-1 infected if they are repeatably reactive ently indeterminate Western blots is probably rare. It by EIA and Western blot indeterminate than if they are does not refute the possibility of prolonged infection in EIA negative, it makes sense to continue to defer indefhigh-risk individuals with persistently indeterminate initely donors with indeterminate Western blots. It will Western blots. It is possible that the seroconversion pebe difficult to implement a reentry algorithm for these riod associated with sexual transmission of HIV-1 is sigdonors or to consider further changes in the deferral crinificantly longer than the 2- to 3-month period reported teria until more studies have been performed 1) to better primarily from studies of infected transfusion recipients define the seroconversionperiod associated with the sexand sexual partners presenting with acute symptomatic ual transmission of HIV-1 and 2) to evaluate the signifinfection. icance of indeterminate Western blot results in a large It is more difficult to explain the discrepancy in number of high-risk individuals and in persons known HIV-1 detection rates in seronegative sexual partners of to seroconvert. HIV-1-infected individuals. It is possible that the sexual Finally, this study does reidorce the Centers for Dispartners in the studies with high detection rates were ease Control recommendation that “a person whose more likely to be infected because of sicker partners, a Western blot test results continue to be consistently ingreater number of unprotected exposures, different sex-
TRANSFUSION 1992-Vol. 32, No. 6
EDITORIAL
determinate for at least six months-in the absence of any known risk factors, clinical symptoms, or other findings-may be considered to be negative for antibodies to HIV-l.”5 This study and others, which have been reported since this recommendation was issued, indicate that such individuals are rarelv. if ever. HIV-1 infected.
J. BROOKSJACKSON, MD, h4BA Department of Pathology Case Westem Reserve University 2085 Adelbert Road Cleveland, OH 44106
17.
18.
19.
20.
References 1. Ward JW, Grindon AJ, Feorino PM, Schable C, Parvin M, Allen JR. Laboratory and epidemiologic evaluation of an enzyme immunoassay for antibodies to HTLV-111. JAMA 1986;256:357-61. 2. Tsang VC, Peralta JM, Simons AR. Enzyme-linked immunoelectrotransfer blot techniques (EITB) for studying the specificities of antigens and antibodies separated by gel electrophoresis. Methods Enzymol 1983;92:377-91. 3. Update: Serologic testing for antibody to human immunodeficiency virus. Morbid Mortal Weekly Rep 1988;36:833-40, 845. 4. Jackson JB, MacDonald KL, Cadwell J, et al. Absence of HIV infection in blood donors with indeterminate Western blot tests for antibody to HIV-1. N Engl J Med 1990;322:217-22. 5. Interpretation and use of Western blot assay for serodiagnosis of human immunodeficiencyvirus type 1 infections. Morbid Mortal Weekly Rep 1989;38(Suppl S-7):l-7. The western immunoblot procedure for HIV 6. Dodd RY, Fang a. antibodies and its interpretation. Arch Pathol Lab Med 1990;114:240-5. 7. Kleinman S. The significance of HIV-1-indeterminate Western blot results in blood donor populations. Arch Pathol Lab Med 1990;114:298-303. 8. Busch MP, El Amad Z, McHugh TM, Chien D, Polito AJ. Reliable confirmation and quantitation of human immunodeficiency virus type antibody using a recombinant-antigen immunoblot assay. Transfusion 1991;31:129-37. 9. Kleinman S, Fitzpatrick L, Secord K, Wilke D. Follow-up testing and notification of anti-HIV Western blot atypical (indeterminant) donors. Transfusion 1988;28:280-2. 10. Dock NL, Kleinman SH, Rayfeld MA, et al. Human immunodeficiency virus infection and indeterminatewestern blot patterns. Prospective studies in a low prevalence population. Arch Intern Med 1991;151:525-30. 11. Goldfarb MF. Effect of heat inactivation on results of HIV antibody testing by Western blot assay (letter). Clin Chem 1988;34:1661-2. 12. Problems created by heat-inactivation of serum specimens before HIV-1 antibody testing. Morbid Mortal Weekly Rep 1989;38:40713. 13. Detection of antibodies to HIV (BiotechlDuPontHIV Western blot kit insert). Wilmington, DE: DuPont Company, 1987. 14. Drabick JJ, Baker JR Jr. HL4 antigen contamination of commercial Western blot strips for detecting human immunodeficiency virus. J Infect Dis 1989;159:357-8. 15. Blomberg J, Vincic E, Honsson C, Medstrand P, Pipkorn R. Identification of regions of HIV-1 p24 reactive with sera which give “indeterminate” results in electrophoretic immunoblots with the help of long synthetic peptides. AIDS Res Hum Retroviruses 1990;6:1363-72. 16. Tribe DE, Reed DL, Lindell P, et al. Antibodies reactive with human immunodeficiencyvirus gag-coded antigens (gag reactive
21. 22. 23.
24.
25.
26.
27. 28. 29.
30. 31. 32. 33. 34.
499 only) are a major cause of enzyme-linked immunosorbent assay reactivity in a blood donor population. J Clin Microbiol 1988;26:641-7. Lange JM, Coutinho RA, Krone WJ, et al. Distinct IgG recognition patterns during progression of subclinical and clinical infection with lymphadenopathy associated virudhuman T lymphotropic virus. Br Med J (Clin Res Ed) 1986;292:228-30. Van der Poel CL. Lelie PN. Reesink HW. et al. Blood donors with indeterminate anti-p2&s reactivity inrHIV-1 western blot: absence of infectivity to transfused patients and in virus culture. Vox Sang 1989;56:162-7. Imagawa DT, Lee MH, Wolinsky SM, et al. Human immunodeficiency virus type 1 infection in homosexual men who remain seronegativefor prolonged periods. N Engl J Med 1989;320:145862. Hewlett IK, Laurian Y,Epstein J, Hawthorne CA, Ruta M, Allain JP. Assessment by gene amplification and serological markers of transmission of HIV-1 from hemophiliacs to their sexual partners and secondarily to their children. J Aquir Immune Defic Syndr 1990;3:714-20. h h e M, Mach B. Identification of HIV-infected seronegative individuals by a direct diagnostic test based on hybridisation to amplified viral DNA. Lancet 1988;2:418-21. Ward JW,Holmberg SD, Allen JR, et al. Transmission of human immunodeficiencyvirus (HIV) by blood transfusions screened as negative for HIV antibody. N Engl J Med 1988;318:473-8. Wolinsky SM, Rinaldo CR, Kwok S, et al. Human immunodeficiency virus type 1 (HIV-1) infection a median of 18 months before a diagnostic western blot. Evidence from a cohort of homosexual men. Ann Intern Med 1989;111:961-72. Eble BE, Busch MP, Khayam-Bashi H, et al. Resolution of infection status of human immunodeficiencyvirus (HIV)-seroindeterminate donors and high-risk seronegative individuals using polymerase chain reaction and virus culture: absence of persistent silent HIV-1 infection in a high prevalence area. Transfusion 1992;32:503-8. Nielsen C, Teglbjaerg LS, Pedersen C, Lundgren JD, Nielsen CM, Vestergaard BF. Prevalence of HIV infection in seronegative high-risk individuals examined by virus isolation and PCR. J Aquir Immune Defic Syndr 1991;4:1107-11. Bailly E, Kleim JP, Schneweis KE, van Loo B, Hammerstein V, Brackman HH. Absence of human immunodeficiencyvirus (HIV) proviral sequences in seronegative hemophilic men and sexual partners of HIV-seropositive hemophiliacs. Transfusion 1992;32 104-8. Mariotti M, Lefrere JJ, Noel B, et al. DNA amplification of HIV-1 in seropositive individuals and in seronegative at-risk individuals. AIDS 1990;4:633-7. Horsburgh CR Jr., Ou CY, Jason J, et al. Concordance of polymerase chain reaction with human immunodeficiencyvirus infection antibody detection. J Infect Dis 1990;162:542-5. Jason J, Ou CY, Moore JL, Lawrence DN, Schochetman G, Evatt BL. Prevalence of human immunodeficiency virus type 1 DNA in hemophilic men and their sex partners. Hemophilia-AIDS Collaborative Study Group. J Infect Dis 1989;160:789-94. Lefrere JJ, Mariotti M, Vittecoq D, et al. No evidence of frequent human immunodeficienciesvirus type 1 infection in seronegative at-risk individuals. Transfusion 1991;31:205-11. Jackson JB, Kwok SY, Hopsicker JS, et al. Absence of HIV-1 infection in antibody-negative sexual partners of HIV-1 infected hemophiliacs. Transfusion 1989;29:265-7. Imagawa D, Detels R. HIV-1 in seronegative homosexual men (letter). N Engl J Med 1991;325:1250-1. Kwok S, Higuchi R. Avoiding false positives with PCR. Nature 1989:339:237-8. FDA-recommendsrevised measures for prevention of HIV transmission through blood and blood components. Blood Bank Week 1992;9(May 1):l-3.
July/August 1992
Number 6
Editorials
Human immunodeficiency virus (H1V)-indeterminate Western blots and latent HIV infection derived from infected cell lines eliminates the reactivity in many of these sample^.^.^ However, despite the use of peptides or recombinant antigens, a significant proportion of these sera continue to show reactivity, which suggests either the presence of antibody to HIV-1, crossreactivity to other viral antigens, or perhaps antibody to the vector (e.g., Escherichiu coli) used to make the recombinant antigen.15J6 Western blot testing of serial samples from persons with true seroconversion reveals that reactivity to p24 is almost always associated with early HIV-1 seroconversion." Therefore, the use of blood from donors with reactivity to the p24 band is especially worrisome, although it should be noted that 10 recipients of blood components from six donors with persistent HIV-1 p24 reactivity showed no evidence of HIV-1 seroconversion by Western blot assay.18 To make matters more confusing, there have been studies reporting the presence of HIV-1 infection in a large percentage of high-risk antibody-negative individual^.'^*^^ For example, Imagawa et aI.l9 reported they were able to culture HIV-1 from the blood of 31 (23%) of 133 seronegative homosexual men, 27 of whom have remained seronegative for up to 36 months after the positive culture. Likewise, Hewlett et al.20 reported that they were able to detect HIV-1 DNA sequences by the polymerase chain reaction (PCR)in the blood of 11(41%) of 27 seronegative sexual partners of HIV1-infected hemophiliacs. HIV-1 transmission from the transfusion of seronegative blood has been documented,22 but these studies suggest that the potential for this to occur may be greater than is currently appreciated. Reports of prolonged seroconversion periods have further heightened anxiety levels. Wolinsky et al.23 tested blood specimens collected from 24 homosexual men at 6-month visits prior to seroconversion. Thirteen of these 24 men had indeterminate Western blots at some point
Licensed enzyme immunoassays (EIAs) are most commonly used for testing the blood of individuals for antibody to human immunodeficiency virus type 1 (HIV-l).l If the patient sample is repeatably reactive by EIA, then the Western blot assay is most often performed to verify the presence of HIV-1 antibody.2 This assay typically reveals six to nine characteristic bands if antibodies to HIV-1 proteins of different molecularweights are p r e ~ e n t .Approximately ~ 99.7 percent of volunteer blood donors at low risk for HIV-1 infection will be negative for HIV-1 antibody by the EIA screening test.4 Of the 0.3 percent who have repeatably reactive samples, 80 percent are Western blot n e g a t i ~ e .However, ~ approximately 20 percent of these persons have one or two bands characteristic of HIV-1 on Western blotting. The reactivity usually is to only one or more of the HIV1 core proteins (p17, p24, and p55) and therefore does not meet the definition of a positive specimen (any two of the following bands present: p24, gp41, and either gp120 or gp160) or a negative specimen (no bands present).5 Such specimens are therefore labeled indeterminate, for lack of a better term. Seroconversion rates of 1 to 5 percent in blood donors who are indeterminate by Western blot have been documented, with the majority of these donors seroconvertingover a period of less than 6 months.69 However, most blood donors with indeterminate Western blots remain persistently indeterminate for years and do not ser~convert.~J~ Thus counseling of donors is difficult, and confidence in the safety of the blood supply is diminished. The cause of most of these atypical Western blot patterns is poorly understood. Atypical Western blot patterns have been associated with heat-related inactivation of serum samples,11J2 in vitro hem~lysis,'~ eleyated bilirubin levels,13 rheumatoid factor,13 polyclonaI gammopathy,13 systemic lupus erythematosus,13 and antibodies to DR human lymphocyte antigens.14 The use of recombinant HIV-1 antigens or peptides instead of viral lysate
497
498
EDITORIAL.
TRANSFUSION
Vol. 32. No. 6-1992
ual practices, and so on. However, I think the differprior to a diagnostic Western blot. HIV-1 DNA was detected by PCR in 20 of the 24 men prior to seroconences are more likely explained by the possibility of version: at 42 months before seroconversion in 2 men; false-positive culture and/or PCR results. In the original study of Imagawa et al.,19 positive at 36 months in 1 man; at 30 months in 1 man; at 24 months in 4 men; at 18 months in 8 men; at 12 months culture results in most of the antibody-negative individuals were not confirmed by PCR or seroconversion. in 1 man; and at 6 months in 3 men. Moreover, this group recently reported32that, in a folThe above studies are disturbing because they suggest low-up study culturing 151 blood samples from 27 anthat the number of Western blot-indeterminateand -seronegative donors who are infected with HIV-1 is greater tibody-negative men who were culture positive in the original study, virus could be isolated from only one than we think. These studies also raise concerns regarding the performance of our serologic screening and conman. Apparently, none of these men had seroconverted. In addition, virus was isolated from only 3 (1.3%) of firmatory assays in detecting HIV-1 infection. Therefore, 230 other antibody-negative men who were continuing it is reassuring Eble et al.24 report, in this issue of to have anal intercourse with more than one person. InTRANSFUSION, that, when they used sensitive PCR complete infection could explain these results, but conand viral culture techniques no HIV-1 infection was detamination or specimen mix-up must be strongly tected in 65 follow-up samples from 26 blood donors considered. with persistently indeterminate Western blots for 1 to 3 Likewise, in the study of Hewlett et al.,zo positive years. At least 60 percent of these donors had at least a PCR resulfs in seronegative women were not confirmed p24 band on Western blot. In addition, HIV-1 infection by viral isolation. Moreover, the extreme sensitivity of was not detected in the blood of 16 persistently seroPCR and the consequent high risk of obtaining false negative heterosexual partners of infected transfusion repositives with PCR, due to carryover from previously cipients nor in the blood of 6 seronegative homosexual amplified material, is well known.33 Almost all laboramen at high risk. In contrast, HIV-1 was detected in all tories with experience in PCR detection have had prob21 antibody-positive individuals tested. lems with false-positive results at one time or another. This report is consistent with at least 10 other studies These false positives may easily be missed unless an that also found no evidence of HIV-1 infection in testing adequate number of negative controls and blinded samthe blood of at least 300 donors who were persistently ples are processed and assayed simultaneouslywith study indeterminate by Western blot and of more than 500 specimens. Blinded samples should not be decoded until high-risk seronegative individuals by PCR and/or viral isolation m e t h ~ d ~ . ~ ~ ~ ~ ~ ~ ~ ~ after ~ ~interpretation ~ ~ - ~of ~results. In contrast, a number of studies, such as the one by How does one explain such diverse findings? The popEble et al. in this issue of TRANSFUSION, have not ulations tested in the different studies may explain some been able to detect HIV-1 infection in high-risk seroof the differences. For example, the likelihood of denegative individuals when the combined application of tecting HIV-1 infection in homosexual men with persistently indeterminate Western blots will be much higher viral culture and PCR have been used. These data are reassuring and support the recent Food and Drug Adminthan that in blood donors at low risk for HIV-1 infection, istration recommendation to change the deferral period because the prevalence of HIV-1 infection is signififor sexual partners of persons with high-risk behavior cantly higher. The study by Eble et al.,” together with from lifetime to 12 months.34 similar studies, only indicates that the presence of However, because it is likely that individuals are more HIV-1 infection in low-risk blood donors with persistlikely to be HIV-1 infected if they are repeatably reactive ently indeterminate Western blots is probably rare. It by EIA and Western blot indeterminate than if they are does not refute the possibility of prolonged infection in EIA negative, it makes sense to continue to defer indefhigh-risk individuals with persistently indeterminate initely donors with indeterminate Western blots. It will Western blots. It is possible that the seroconversion pebe difficult to implement a reentry algorithm for these riod associated with sexual transmission of HIV-1 is sigdonors or to consider further changes in the deferral crinificantly longer than the 2- to 3-month period reported teria until more studies have been performed 1) to better primarily from studies of infected transfusion recipients define the seroconversionperiod associated with the sexand sexual partners presenting with acute symptomatic ual transmission of HIV-1 and 2) to evaluate the signifinfection. icance of indeterminate Western blot results in a large It is more difficult to explain the discrepancy in number of high-risk individuals and in persons known HIV-1 detection rates in seronegative sexual partners of to seroconvert. HIV-1-infected individuals. It is possible that the sexual Finally, this study does reidorce the Centers for Dispartners in the studies with high detection rates were ease Control recommendation that “a person whose more likely to be infected because of sicker partners, a Western blot test results continue to be consistently ingreater number of unprotected exposures, different sex-
TRANSFUSION 1992-Vol. 32, No. 6
EDITORIAL
determinate for at least six months-in the absence of any known risk factors, clinical symptoms, or other findings-may be considered to be negative for antibodies to HIV-l.”5 This study and others, which have been reported since this recommendation was issued, indicate that such individuals are rarelv. if ever. HIV-1 infected.
J. BROOKSJACKSON, MD, h4BA Department of Pathology Case Westem Reserve University 2085 Adelbert Road Cleveland, OH 44106
17.
18.
19.
20.
References 1. Ward JW, Grindon AJ, Feorino PM, Schable C, Parvin M, Allen JR. Laboratory and epidemiologic evaluation of an enzyme immunoassay for antibodies to HTLV-111. JAMA 1986;256:357-61. 2. Tsang VC, Peralta JM, Simons AR. Enzyme-linked immunoelectrotransfer blot techniques (EITB) for studying the specificities of antigens and antibodies separated by gel electrophoresis. Methods Enzymol 1983;92:377-91. 3. Update: Serologic testing for antibody to human immunodeficiency virus. Morbid Mortal Weekly Rep 1988;36:833-40, 845. 4. Jackson JB, MacDonald KL, Cadwell J, et al. Absence of HIV infection in blood donors with indeterminate Western blot tests for antibody to HIV-1. N Engl J Med 1990;322:217-22. 5. Interpretation and use of Western blot assay for serodiagnosis of human immunodeficiencyvirus type 1 infections. Morbid Mortal Weekly Rep 1989;38(Suppl S-7):l-7. The western immunoblot procedure for HIV 6. Dodd RY, Fang a. antibodies and its interpretation. Arch Pathol Lab Med 1990;114:240-5. 7. Kleinman S. The significance of HIV-1-indeterminate Western blot results in blood donor populations. Arch Pathol Lab Med 1990;114:298-303. 8. Busch MP, El Amad Z, McHugh TM, Chien D, Polito AJ. Reliable confirmation and quantitation of human immunodeficiency virus type antibody using a recombinant-antigen immunoblot assay. Transfusion 1991;31:129-37. 9. Kleinman S, Fitzpatrick L, Secord K, Wilke D. Follow-up testing and notification of anti-HIV Western blot atypical (indeterminant) donors. Transfusion 1988;28:280-2. 10. Dock NL, Kleinman SH, Rayfeld MA, et al. Human immunodeficiency virus infection and indeterminatewestern blot patterns. Prospective studies in a low prevalence population. Arch Intern Med 1991;151:525-30. 11. Goldfarb MF. Effect of heat inactivation on results of HIV antibody testing by Western blot assay (letter). Clin Chem 1988;34:1661-2. 12. Problems created by heat-inactivation of serum specimens before HIV-1 antibody testing. Morbid Mortal Weekly Rep 1989;38:40713. 13. Detection of antibodies to HIV (BiotechlDuPontHIV Western blot kit insert). Wilmington, DE: DuPont Company, 1987. 14. Drabick JJ, Baker JR Jr. HL4 antigen contamination of commercial Western blot strips for detecting human immunodeficiency virus. J Infect Dis 1989;159:357-8. 15. Blomberg J, Vincic E, Honsson C, Medstrand P, Pipkorn R. Identification of regions of HIV-1 p24 reactive with sera which give “indeterminate” results in electrophoretic immunoblots with the help of long synthetic peptides. AIDS Res Hum Retroviruses 1990;6:1363-72. 16. Tribe DE, Reed DL, Lindell P, et al. Antibodies reactive with human immunodeficiencyvirus gag-coded antigens (gag reactive
21. 22. 23.
24.
25.
26.
27. 28. 29.
30. 31. 32. 33. 34.
499 only) are a major cause of enzyme-linked immunosorbent assay reactivity in a blood donor population. J Clin Microbiol 1988;26:641-7. Lange JM, Coutinho RA, Krone WJ, et al. Distinct IgG recognition patterns during progression of subclinical and clinical infection with lymphadenopathy associated virudhuman T lymphotropic virus. Br Med J (Clin Res Ed) 1986;292:228-30. Van der Poel CL. Lelie PN. Reesink HW. et al. Blood donors with indeterminate anti-p2&s reactivity inrHIV-1 western blot: absence of infectivity to transfused patients and in virus culture. Vox Sang 1989;56:162-7. Imagawa DT, Lee MH, Wolinsky SM, et al. Human immunodeficiency virus type 1 infection in homosexual men who remain seronegativefor prolonged periods. N Engl J Med 1989;320:145862. Hewlett IK, Laurian Y,Epstein J, Hawthorne CA, Ruta M, Allain JP. Assessment by gene amplification and serological markers of transmission of HIV-1 from hemophiliacs to their sexual partners and secondarily to their children. J Aquir Immune Defic Syndr 1990;3:714-20. h h e M, Mach B. Identification of HIV-infected seronegative individuals by a direct diagnostic test based on hybridisation to amplified viral DNA. Lancet 1988;2:418-21. Ward JW,Holmberg SD, Allen JR, et al. Transmission of human immunodeficiencyvirus (HIV) by blood transfusions screened as negative for HIV antibody. N Engl J Med 1988;318:473-8. Wolinsky SM, Rinaldo CR, Kwok S, et al. Human immunodeficiency virus type 1 (HIV-1) infection a median of 18 months before a diagnostic western blot. Evidence from a cohort of homosexual men. Ann Intern Med 1989;111:961-72. Eble BE, Busch MP, Khayam-Bashi H, et al. Resolution of infection status of human immunodeficiencyvirus (HIV)-seroindeterminate donors and high-risk seronegative individuals using polymerase chain reaction and virus culture: absence of persistent silent HIV-1 infection in a high prevalence area. Transfusion 1992;32:503-8. Nielsen C, Teglbjaerg LS, Pedersen C, Lundgren JD, Nielsen CM, Vestergaard BF. Prevalence of HIV infection in seronegative high-risk individuals examined by virus isolation and PCR. J Aquir Immune Defic Syndr 1991;4:1107-11. Bailly E, Kleim JP, Schneweis KE, van Loo B, Hammerstein V, Brackman HH. Absence of human immunodeficiencyvirus (HIV) proviral sequences in seronegative hemophilic men and sexual partners of HIV-seropositive hemophiliacs. Transfusion 1992;32 104-8. Mariotti M, Lefrere JJ, Noel B, et al. DNA amplification of HIV-1 in seropositive individuals and in seronegative at-risk individuals. AIDS 1990;4:633-7. Horsburgh CR Jr., Ou CY, Jason J, et al. Concordance of polymerase chain reaction with human immunodeficiencyvirus infection antibody detection. J Infect Dis 1990;162:542-5. Jason J, Ou CY, Moore JL, Lawrence DN, Schochetman G, Evatt BL. Prevalence of human immunodeficiency virus type 1 DNA in hemophilic men and their sex partners. Hemophilia-AIDS Collaborative Study Group. J Infect Dis 1989;160:789-94. Lefrere JJ, Mariotti M, Vittecoq D, et al. No evidence of frequent human immunodeficienciesvirus type 1 infection in seronegative at-risk individuals. Transfusion 1991;31:205-11. Jackson JB, Kwok SY, Hopsicker JS, et al. Absence of HIV-1 infection in antibody-negative sexual partners of HIV-1 infected hemophiliacs. Transfusion 1989;29:265-7. Imagawa D, Detels R. HIV-1 in seronegative homosexual men (letter). N Engl J Med 1991;325:1250-1. Kwok S, Higuchi R. Avoiding false positives with PCR. Nature 1989:339:237-8. FDA-recommendsrevised measures for prevention of HIV transmission through blood and blood components. Blood Bank Week 1992;9(May 1):l-3.
