Sayre K R, Dodd R Y, Tegtmeier G, Layug L, Alexander S S, Busch M P
Ortho Diagnostics Systems, Inc., Raritan, New Jersey, USA.
Transfusion. 1996 Jan;36(1):45-52. doi: 10.1046/j.1537-2995.1996.36196190514.x.
The manufacturers' criteria for a positive human immunodeficiency virus type 1 (HIV-1) Western blot (WB) test were recently revised to require reactivity to only two of the following bands: p24, gp41, and gp120/160. In a recent report, low-risk blood donors were identified in whom nonspecific reactivity to multiple env antigens in WB testing resulted in apparently false-positive WBs by these criteria. The present study was conducted to verify the existence of false-positive WBs among noninfected donors and to assess the extent of this problem.
Four donors classified as WB-positive on the basis of env-only (3 cases) or p24/env-only (1 case) patterns were investigated. Index and/or follow-up specimens were tested by polymerase chain reaction (PCR), by overlapping recombinant env antigens and synthetic peptides in enzyme immunoassays, and by deglycosylated and denatured antigen WBs. WB records from American Red Cross blood centers were reviewed to determine the frequency of env-only and p24/env-only patterns, relative to all positive WBs, from 1988 through 1993.
The four index-case donors denied risk and had stable WB reactivity during follow-up. HIV PCR was negative in all. Env reactivity was restricted to nonglycosylated gp41 epitopes; no gp120-specific reactivity was detected. For three of the four donors, env reactivity was mapped to a 20-amino acid N-terminal epitope of gp41. The rate of detecting WBs with these false-positive patterns increased from 0.6 percent of all positive WBs from 1988 to 1990 (4/776) to 8 percent in 1991 and 1992 (52/683), and then it declined to 6 percent in 1992 and 1993 (47/783). Env-only patterns predominated in 1991 and 1992, whereas p24/env-only patterns were more frequent following implementation of combined anti-HIV-1/HIV type 2 enzyme immunoassays in 1992.
Low-risk blood donors can have false-positive results on WB tests. Increased detection of env-only and p24/env-only WBs appears related to the enhanced sensitivity of newer enzyme immunoassays to gp41 and p24 antibodies. Donors with these patterns should undergo follow-up testing to document the presence or absence of HIV infection.
1型人类免疫缺陷病毒（HIV-1）免疫印迹法（WB）检测呈阳性的制造商标准最近进行了修订，要求仅对以下条带中的两条有反应性：p24、gp41和gp120/160。在最近的一份报告中，发现低风险献血者在WB检测中对多种env抗原的非特异性反应导致根据这些标准出现明显的WB假阳性结果。本研究旨在验证未感染献血者中WB假阳性的存在，并评估该问题的严重程度。
对4名根据仅env（3例）或仅p24/env（1例）模式被分类为WB阳性的献血者进行了调查。通过聚合酶链反应（PCR）、在酶免疫测定中使用重叠重组env抗原和合成肽以及通过去糖基化和变性抗原WB对索引和/或随访标本进行检测。回顾了美国红十字会血液中心的WB记录，以确定1988年至1993年期间仅env和仅p24/env模式相对于所有阳性WB的频率。
4名索引病例献血者否认有风险行为，且在随访期间WB反应性稳定。所有病例的HIV PCR均为阴性。env反应性仅限于非糖基化的gp41表位；未检测到gp12o特异性反应性。对于4名献血者中的3名，env反应性定位到gp41的一个20个氨基酸的N端表位。出现这些假阳性模式的WB检测率从1988年至1990年占所有阳性WB的0.6%（4/776）增加到1991年和1992年的8%（52/683），然后在1992年和1993年降至6%（47/783）。仅env模式在1991年和1992年占主导，而在1992年实施1型和/或2型人类免疫缺陷病毒联合酶免疫测定后，仅p24/env模式更为常见。
低风险献血者的WB检测可能出现假阳性结果。仅env和仅p24/env的WB检测增加似乎与新型酶免疫测定对gp41和p24抗体的敏感性提高有关。有这些模式的献血者应接受随访检测，以确定是否感染HIV。
