高灵敏度C-反应蛋白酶免疫分析及其临床应用

本文建立了高灵敏度C-反应蛋白的酶免疫分析(hs-CRP EIA或hs-CRP ELISA)方法.取抗CRP单克隆抗体C1在0.05mol/L pH9.0的碳酸缓冲液中将其包被在板条微孔内,成为固相抗体,以过碘酸钠方法将抗CRP单抗E11与辣根过氧化物酶相联结,成为标记抗体,与不同量的CRP标准品在磷酸缓冲液中保温反应,完成标准曲线.Bmax/B0为61.5,非特异结合小于1.6%,灵敏度小于0.1mg/L,批内CV为5.8%,批间CV为11.5%,回收率为98.8%.测定正常人450名:包括50岁以下270名,其中男160名、女110名,血清hs-CRP分别为1.34±0.80mg/L和1.25±0.92mg/L;50岁以上180名,其中男96名、女84名,hs-CRP分别为2.23±1.21mg/L和2.01±1.45mg/L.50岁以上组,血清hs-CRP值显著高于50岁以下组(P<0.01).测定急性心肌梗死12例,血清hs-CRP为51.6±20.1mg/L,显著高于正常人组(P<0.0001),其他心血管疾病14例,hs-CRP也都显著高于正常人组(P<0.001),肺癌10例,hs-CRP为18.2±8.34mg/L,显著高于正常人组(P<0.001),其他肿瘤14例,hs-CRP也都显著高于正常人组(P<0.001).新建hs-CRP ELISA与现行hs-CRP IRMA具有良好的相关性:Y=0.9198X, r2=0.9186.     

尿视黄醇结合蛋白酶免疫测定法的建立和初步应用

我们自制兔（抗人ＲＢＰ）ＩｇＧ－ＨＲＰ酶标记物，建立了一种灵敏、简便、可靠的尿视黄醇结合蛋白（ＲＢＰ）双抗体夹心酶免疫测定法。方法灵敏度为０．４ｎｇ／ｍｌ；批内Ｃ．Ｖ．６．３％，批间Ｃ．Ｖ．１４．１％；工作范围０．４～５０ｎｇ／ｍｌ。本法的１００例正常健康人（２０～７４岁，平均４６岁）的尿ＲＢＰ值，以μｇ／ｍｍｏｌＣｒ表示，其算术均数（）±标准差（ｓ）为１１．２±６．０１；几何均数和９５％位点分别为９．５和２２。１０２例尿Ａ１ｂ正常的糖尿病患者，其尿ＲＢＰ值为４５．３±１０５．７μｇ／ｍｍｏｌＣｒ，较正常人明显增高（Ｐ＜０．００１），其中４０例（占３９．３％）高于正常上限。２５例肾功能正常的慢性肾盂肾炎中有２１例（占８４％）以及２４例其它各种肾小管间质疾病中的２２例（占９１．７％），尿ＲＢＰ值超越正常上限。肾小管损害可以是糖尿病肾病的一种早期症状。尿ＲＢＰ是近曲肾小管损害的一项敏感指标，对肾小管间质疾病的早期诊断具有重要价值。     

乙肝病毒前S2抗原发光酶免疫方法的临床应用

建立乙肝病毒前Ｓ２抗原发光酶免疫方法，检测ＨＢＶ感染者血清，肝组织及其细胞器中的前Ｓ２，结果与ＨＢｅＡｇ，ＨＢｃＡｇ，ＨＢＶ ＤＮＡ等复制指标一致，某些肝内ＨＢＶ ＤＮＡ阴性者ＰＳ２阳性。这提示前Ｓ２是ＨＢＶ活跃复制的指标。前Ｓ２在肝内主要存于微粒体和核糖体中。前Ｓ２抗体阳性，与肝细胞破坏有关，急性和慢迁肝预示恢复，慢活肝，肝硬化和肝癌预示恶化。本法集发光反应的快速敏感及免疫反应的特异性于一身，敏     

Incorporation of Different Bridge Length Linkers in Enzyme and Its Use in the Preparation of Enzyme Conjugates for Immunoassay

Abstract

An enzyme horseradish peroxidase (HRP), as a starting material, has been used to introduce different bridge length linkers, and its use in the preparation of enzyme conjugates for immunoassay is described. HRP was conjugated to adipic acid dihydrazide (ADH), gamma amino butyric acid (GABA), followed by ADH and 6‐amino caproic acid (6ACA) followed by ADH. The different bridge length linkers‐incorporated enzyme was coupled to a carboxylic derivative of cortisol. Four enzyme conjugates with different bridge length were prepared, such as cortisol‐21‐hemisuccinate–HRP (cortisol‐21‐HS–HRP), cortisol‐21‐HS–ADH–HRP, cortisol‐21‐HS–ADH–GABA–HRP, and cortisol‐21‐HS–ADH–6ACA–HRP. The influence of linker on sensitivity and specificity of the cortisol assay was studied. The study revealed that incorporation of a linker between hapten and enzyme increases the sensitivity and specificity of the assay.     

化学发光法和酶联免疫法作为筛选试验测定丙肝抗体的评价

目的比较化学发光法(CLIA)和酶联免疫法(EIA)测抗-HCV对诊断HCV感染的检出率,分析CLIA测定抗-HCV作为HCV感染初筛试验的重要临床意义。方法分别用CLIA、EIA方法检测所有临床标本中的抗-HCV,选取抗-HCV初筛阳性样本进行HCV RNA确认试验。结果 6461例样本中,EIA和CLIA测抗-HCV阳性率分别为2.86%和3.17%;确认试验中,CLIA法抗-HCV阳性与HCV RNA的符合率为97.1%,显著高于EIA组(91.9%)。EIA法测抗-HCV,S:CO>5.0以上,与HCV RNA检测符合率可达100%;弱阳性样本,与HCV RNA符合率为69.7%;CLIA法测抗-HCV,S:CO>2.0以上,与HCV RNA检测符合率可达100%;弱阳性样本,与HCV RNA符合率为92.9%。有31例样本CLIA法抗-HCV和HCV RNA阳性,而EIA法抗-HCV阴性;有4例样本EIA法检测为阳性,而CLIA法和PCR确认试验均为阴性。结论CLIA法测抗-HCV作为HCV感染初筛实验,与传统EIA相比,特异性和阳性预测值更高,有效降低了假阳性率,有利于临床医生对HCV感染患者的早期诊断和治疗。     

Evaluation of the Specificity of Two Enzyme Immunoassays for Coccidioidomycosis by Using Sera from a Region of Endemicity and a Region of Nonendemicity

Coccidioidomycosis (CM), a serious life-threatening fungal infection endemic to arid regions of the western United States and Mexico, can be challenging to diagnose in a timely manner. Commercially developed enzyme immunoassays (EIAs) (from Meridian Biosciences and Immuno-Mycologics [IMMY]) have provided faster, simpler means for serodiagnosis; however, independent evaluations have questioned EIA specificity, particularly IgM-positive/IgG-negative results. This study was conducted to evaluate EIA specificity among persons residing in Puerto Rico (n = 534), where CM is not endemic (who were not likely to have been exposed to Coccidioides spp.), compared to blood bank donors residing in Arizona (n = 1,218), where CM is endemic. Upon comparing serum reactivity between Puerto Rico and Arizona, the Meridian EIA showed a significant difference in IgG reactivity (0.37% versus 3.6%; P < 0.001) but not IgM reactivity (3.4% versus 2.4%; P = 0.31). No IgM-/IgG-reactive sera were detected among sera from Puerto Rico, compared to 7 (0.57%) sera from Arizona. Similar results were observed using the IMMY EIA, although significantly (P = 0.03) fewer IgM-reactive sera from Arizona were observed, compared to the Meridian EIA. EIA-reactive sera were also evaluated by immunodiffusion before and after 3- to 4-fold concentration of the sera. These results demonstrate that elevated IgG EIA reactivity is present in sera from healthy individuals in regions of endemicity and that IgM EIA reactivity observed in sera from individuals residing outside regions of endemicity is most likely nonspecific. Other criteria, including clinical and microbiological evaluations, should be taken into account when interpreting results from surveillance studies and other reporting measures.     

An Enzyme Immunoassay for the Detection of Antisperm Antibodies

ABSTRACT: A simple and reliable enzyme-linked immunosorbent assay (ELISA) for the detection of antisperm antibodies has been developed in our laboratory. The antigen for the solid phase was produced by sperm sonication while antihuman globulin conjugated to alkaline phosphatase was used as the developing reagent. The conditions and reagents of the assay were chosen to give a mild treatment of the antigen, simple manipulation during washing steps, and nontoxic and readily available reagents. The results were compared to a conventional microscopical method routinely used in our laboratory that detects agglutinating antibodies to human spermatozoa. In 96% of all cases antibodies detected by the microscopical method were also detected by ELISA. Moreover there were some cases where no antisperm antibodies could be demonstrated by microscopy, but gave a positive reaction with ELISA. These were usually cases of unexplained oligospermia, agglutinates in the ejaculate, and bad motility or low viability of the sperms. These results, and also titration experiments of positive samples demonstrate the higher sensitivity of the ELISA by comparison with microscopical methods.     

Performance of a Cytomegalovirus IgG Enzyme Immunoassay Kit Modified To Measure Avidity

The measurement of cytomegalovirus (CMV) IgG avidity accurately discriminates recent and past CMV infections. We sought to determine if the Wampole Laboratories CMV IgG enzyme immunoassay (EIA) could be modified to measure avidity. The evaluation panel consisted of 156 serum samples we used in 2002 to validate a laboratory-developed EIA, in which 78 serum samples exhibited low avidity, 7 exhibited intermediate avidity, and 71 exhibited high avidity. The qualitative agreement between the two avidity assays was 94% (147/156); all 9 sera with discordant results exhibited intermediate avidity in one of the assays. The avidity index (AI) values in the two assays showed excellent correlation (r = 0.96, P < 0.0001). The definition of high avidity was verified for the Wampole assay by demonstrating high avidity in 91/93 (98%) recently collected CMV IgG-positive/IgM-negative serum samples. The performance of the Wampole avidity assay in a reference laboratory setting was assessed using 470 consecutive serum samples submitted for CMV IgG avidity testing. Surprisingly, 101 serum samples were negative when screened for CMV IgG using the Wampole kit per the package insert; 98 of these 101 serum samples were tested using a CMV IgG chemiluminescent immunoassay, and only 5 were positive. Of the 369 CMV IgG-positive samples, 6% exhibited low IgG avidity, 6% exhibited intermediate avidity, and 88% exhibited high avidity; CMV IgM detection rates were inversely related to AI levels. These findings show that (i) the Wampole CMV IgG EIA can be modified to measure CMV IgG avidity, (ii) many samples are apparently submitted for avidity testing without knowledge of their CMV IgG status, and (iii) most CMV IgG-positive sera submitted for avidity testing exhibit high avidity.     

微粒子酶联免疫分析法与电化学发光免疫分析法测定甲型肝炎病毒抗体一致性评价

为对微粒子酶联免疫分析法（MEIA）测定甲型肝炎病毒抗体方法学进行验证,用MEIA与电化学发光免疫分析法（ECLIA）同时检测476份血清标本的甲型肝炎病毒抗体,对其测量准确性、特异性及重复性进行评估分析。结果表明,MEIA与ECLIA比较,阳性符合率为98.7%,阴性符合率为97.0%,总符合率为98.3%。类风湿因子（RF）阳性、重度溶血、脂血、黄疸血清对检测无明显影响。MEIA与ECLIA测定甲型肝炎病毒抗体一致性较高。     

Clinical Validation of the Cervista HPV HR Test According to the International Guidelines for Human Papillomavirus Test Requirements for Cervical Cancer Screening

This study demonstrates that both the clinical sensitivity and specificity of the Cervista HPV HR test for high-risk human papillomavirus (HPV) detection are not inferior to those of the Hybrid Capture 2 (HC2) test. The intra- and interlaboratory reproducibilities of Cervista were 92.0% (kappa, 0.83) and 90.4% (kappa, 0.80), respectively. The Cervista HPV HR test fulfills all the international HPV test requirements for cervical primary screening purposes.     

高灵敏均相酶免疫法测定血清皮质醇方法建立与性能评价

目的 建立高灵敏均相酶免疫法定量检测血清皮质醇.方法 对此方法的线性范围、准确度、精密度、抗干扰能力、临床可报告范围以及参考区间进行性能验证.结果 本研究建立的血清皮质醇均相酶免疫测定方法,线性范围为30.0～1200.0ng/mL,准确度相对偏差B≤10.0％,批内CV≤10.0％,批间差R≤10.0％,当样本中胆红素≤50mg/L、血红蛋白≤1000mg/L、白蛋白≤100g/L、抗坏血酸≤176mg/dL时,对测定结果无影响,临床可报告范围上限6500ng/mL,血清皮质醇参考区间为60～230ng/mL.结论 该均相酶免疫法能够满足临床血清皮质醇检测的需求,可以进一步推广至临床使用.     

化学发光免疫法测定人体甲状腺激素的性能验证及其临床应用

目的 评估化学发光免疫系统在临床甲状腺素检测中的应用效果.方法 选取我院2018年6月至2019年11月区间内的100例甲亢患者、100例甲低患者和100例甲状腺功能正常者作为试验对象,将化学发光免疫法(CLIA)与酶联免疫吸附法(ELISA)、放射免疫测定法(RAI)检测结果比较.结果 使用化学发光免疫系统实测血清促甲状腺素(TSH)、游离三碘甲状腺原氨酸(FT3)、游离甲状腺素(FT4)时,所得线性范围、准确度、总精密度均较好,标准变异系数(CV)1.58％～6.44％、灵敏度较高且方法总回收率在99.7％～104.6％;且实际样本检测结果优于ELISA法、RAI法.结论 利用化学发光免疫法对甲状腺功能异常患者进行血清中甲状腺素及其抗体检测,可显著提高检测结果准确性并缩短检测周期,具有较高的临床医学推广价值.     

Novel Recombinant-Antigen Enzyme Immunoassay for Serological Diagnosis of Syphilis

Enzyme immunoassay (EIA) is an ideal method for screening large numbers of patients for syphilis. We evaluated a novel immune-capture EIA (ICE Syphilis; Murex Diagnostics) that uses three recombinant Treponema pallidum antigens (TpN15, TpN17, and TpN47) and compared the results with those obtained by the native T. pallidum antigen EIA (Captia SelectSyph-G; Centocor) that we currently use for the serodiagnosis of syphilis. Specificity was evaluated by screening 1,184 unselected serum specimens in parallel by the ICE Syphilis and SelectSyph-G assays, while sensitivity was tested with a panel of 101 serum specimens containing antitreponemal antibodies (treated and untreated) from patients with various stages of infection. The specificity of the ICE Syphilis EIA (99.8%) on screening was significantly higher (P < 0.02) than that of the SelectSyph-G EIA (99.2%). The sensitivity of the ICE Syphilis EIA was significantly higher (P < 0.01) than that of the SelectSyph-G EIA on both initial (99 versus 91.4%) and repeat (100 versus 92.4%) testing. The ICE Syphilis EIA was also significantly more sensitive (P < 0.01) than the fluorescent treponemal antibody-abs (92.4%) but not the T. pallidum hemagglutination assay (97.1%). Sera containing antitreponemal antibodies gave a much higher antibody index (absorbance of test serum/kit cutoff) by the ICE Syphilis EIA than by the SelectSyph-G EIA. This combined with the overall high sensitivity makes the ICE Syphilis EIA an ideal test for excluding or detecting treponemal infection in human immunodeficiency virus (HIV)-infected patients. The ICE Syphilis EIA was positive with sera from all 15 HIV-infected patients in the study, whereas sera from 3 HIV-infected patients were negative by the SelectSyph-G EIA. We conclude that the high sensitivity and specificity of the ICE Syphilis EIA and its suitability for automation make it an ideal screening test.     

Hs-CRP酶免疫分析与免疫比浊法灵敏度比较

利用我国首获批准文号的hs-CRP酶免疫分析试剂盒与hs-CRP免疫比浊法检测了80名正常人,比较两种方法的灵敏度。结果显示：酶免疫分析的检测下限为0.01mg/L,免疫比浊法为0.5mg/L。酶免疫分析法测得50岁以下组CRP值在1mg/L以下者占60%,用免疫比浊法检测,本组全部CRP测定值都大于1mg/L;酶免疫分析法测得50岁以上组CRP值在1mg/L以下者占35%,用免疫比浊法测得该组CRP值全部都大于1mg/L。对比两种方法的x±s,酶免疫分析法在50岁以下组为1.05±1.24mg/L,免疫比浊法为2.52±1.85mg/L;酶免疫分析法在50岁以上组为1.95±1.29mg/L,免疫比浊法为3.00±1.25mg/L。免疫比浊法测定的正常人群CRP值偏高（P〈0.01）。本文结果表明,免疫比浊法对80名正常人的CRP测定值全部大于1mg/L,说明其灵敏度不能满足国际上心血管事件风险评估新标准规定的1mg/L以下为低风险区的检测需要。     

Performance of a New Rapid Immunoassay Test Kit for Point-of-Care Diagnosis of Significant Bacteriuria

Urinary tract infections (UTIs) are frequently encountered in clinical practice and most commonly caused by Escherichia coli and other Gram-negative uropathogens. We tested RapidBac, a rapid immunoassay for bacteriuria developed by Silver Lake Research Corporation (SLRC), compared with standard bacterial culture using 966 clean-catch urine specimens submitted to a clinical microbiology laboratory in an urban academic medical center. RapidBac was performed in accordance with instructions, providing a positive or negative result in 20 min. RapidBac identified as positive 245/285 (sensitivity 86%) samples with significant bacteriuria, defined as the presence of a Gram-negative uropathogen or Staphylococcus saprophyticus at ≥10³ CFU/ml. The sensitivities for Gram-negative bacteriuria at ≥10⁴ CFU/ml and ≥10⁵ CFU/ml were 96% and 99%, respectively. The specificity of the test, detecting the absence of significant bacteriuria, was 94%. The sensitivity and specificity of RapidBac were similar on samples from inpatient and outpatient settings, from male and female patients, and across age groups from 18 to 89 years old, although specificity was higher in men (100%) compared with that in women (92%). The RapidBac test for bacteriuria may be effective as an aid in the point-of-care diagnosis of UTIs especially in emergency and primary care settings.     

Evaluation of Oral Fluid Enzyme Immunoassay for Confirmation of a Positive Rapid Human Immunodeficiency Virus Test Result

The CDC recommends that a reactive rapid human immunodeficiency virus (HIV) test be confirmed with an approved supplemental test; the performance of an intermediate enzyme immunoassay (EIA) is optional. In support of this recommendation, it was found that of 1,431 reactive rapid HIV test results, 2 (0.1%) had false-negative oral fluid Western blot results and both had false-negative EIA results.Until 2002 in the United States, all tests for human immunodeficiency virus (HIV) infection were conducted in laboratories and the results were reported within several days to 2 weeks. Beginning in 2003, rapid HIV tests waived under the Clinical Laboratory Improvement Amendments of 1988 became available. The rapid tests can be performed with finger-stick whole-blood or oral fluid specimens in nonclinical settings, and the results (negative or preliminary positive) are available within an hour. Negative rapid test results may be reported without further testing. However, preliminary positive rapid test results must be confirmed in a laboratory with a supplemental test (e.g., a Western blot [WB] test) (2, 3). WB results from serum specimens are more accurate than WB results from oral fluid specimens, but because phlebotomy is not always feasible in nonclinical settings, some HIV testing programs use oral fluid for WB confirmation of rapid tests (4) (OraSure HIV type 1 [HIV-1] WB kit package insert; OraSure, Inc., Bethlehem, PA). Before 2007, the CDC recommended that a laboratory-based enzyme immunoassay (EIA) and a WB test be performed when oral fluid specimens were submitted for confirmation of positive rapid tests. In 2007, the CDC changed this recommendation because of the impending withdrawal of the only Food and Drug Administration (FDA)-approved oral fluid EIA and because postmarketing surveillance data identified several instances in which the oral fluid EIA was negative in persons whose rapid tests and oral fluid or serum WB were positive (1, 2). To evaluate the additional diagnostic usefulness of an oral fluid EIA to confirm preliminary positive rapid test results, the CDC examined the EIA and WB results for oral fluid specimens from persons confirmed to be HIV infected by serum WB.Study participants were persons with known HIV infection who had not taken antiretroviral treatment during the past 3 months. During the period from March 2006 to August 2007, 1,436 participants, all confirmed to be HIV infected by serum WB, were enrolled at clinics in six cities (Atlanta, GA; Baltimore, MD; Chicago, IL; Denver, CO; Louisville, KY; and Philadelphia, PA). Participants provided finger-stick whole-blood and oral fluid specimens, which were tested by the OraQuick Advance Rapid HIV-1/2 antibody test (OraSure, Inc., Bethlehem, PA) at the study site. Additional oral fluid specimens were collected using an OraSure HIV-1 oral specimen collection device and tested with the Vironostika HIV-1 Microelisa system EIA (bioMérieux, Marcy-l''Etoile, France) and the OraSure HIV-1 WB. The oral fluid EIA was not conducted for 429 specimens because of the unavailability of test kits due to a manufacturer shortage. Serum specimens were collected using standard BD Vacutainer tubes (Becton, Dickinson and Company, Franklin Lakes, NJ) and tested with the Genetic Systems HIV-1/HIV-2 Plus O EIA and HIV-1 WB (Bio-Rad, Redmond, WA).Specimens from 5 of the 1,436 participants were excluded from analysis: two specimens were suspected of having an error in identification labeling, and three oral fluid specimens had insufficient volume for confirmatory testing. All whole-blood (n = 1,431) and oral fluid (n = 1,429) specimens tested positive using the OraQuick rapid test. All serum specimens (n = 1,431) tested positive by serum WB. Of the 1,431 oral fluid specimens tested by oral fluid WB, 1,423 (99.4%) were positive, six (0.4%) were indeterminate, and two (0.1%) were negative. Oral fluid EIAs were performed on 994 of the 1,423 specimens that had positive oral fluid WB results, and all 994 oral fluid EIAs were reactive. Of the six oral fluid specimens with indeterminate WB results, five of six (83.3%) were positive by oral fluid EIA. Of the two oral fluid WB-negative specimens, neither was positive by oral fluid EIA.Data from this study indicate that oral fluid WB tests were positive in 99.4% of specimens from persons who were known to be HIV infected. However, specimens from approximately 0.1% of HIV-infected persons had false-negative oral fluid WB results, and both of these specimens also had false-negative oral fluid EIA results. Specimens from six (0.4%) HIV-infected persons had indeterminate oral fluid WB results, and one of these specimens had false-negative results for oral fluid EIA. Current guidelines require additional confirmatory testing using a blood specimen for any persons with a positive rapid test and a negative or indeterminate oral fluid WB (3). For these persons, even if there is a positive oral fluid EIA result, they will still need a follow-up WB.Postmarketing surveillance conducted in 2003 to monitor the performance of the OraQuick test indicated that some HIV-infected persons with preliminary positive rapid test results had false-negative oral fluid EIA results (2). In addition, the only FDA-approved oral fluid EIA was withdrawn from the market (1). The results of this study support current CDC recommendations that all preliminary positive rapid test results be confirmed with an additional approved supplemental test for HIV, such as WB or an immunofluorescence assay, and that performing an intermediate EIA is optional (2, 3). The CDC further recommends that if WB confirmatory testing of an oral fluid specimen produces a negative or an indeterminate result, confirmatory testing should be repeated with a blood specimen because of its greater sensitivity (2, 3).     

Quantitation of Immunoglobulin to Hepatitis E Virus by Enzyme Immunoassay

We developed a quantitative enzyme immunoassay (EIA) for antibody to hepatitis E virus (HEV) by using truncated HEV capsid protein expressed in the baculovirus system to improve seroepidemiology, to contribute to hepatitis E diagnosis, and to enable vaccine evaluations. Five antigen lots were characterized; we used a reference antiserum to standardize antigen potency. We defined Walter Reed antibody units (WR U) with a reference antiserum by using the four-parameter logistic model, established other reference pools as assay standards, and determined the conversion factor: 1 WR U/ml = 0.125 World Health Organization unit (WHO U) per ml. The EIA performed consistently; median intra- and intertest coefficients of variation were 9 and 12%, respectively. The accurate minimum detection limit with serum diluted 1:1,000 was 5.6 WR U/ml; the test could detect reliably a fourfold antibody change. In six people followed from health to onset of hepatitis E, the geometric mean antibody level rose from 7.1 WR U/ml to 1,924.6 WR U/ml. We used the presence of 56- and 180-kDa bands by Western blotting as a confirmatory test and to define true-negative and -positive serum specimens. A receiver-operating characteristics plot identified 30 WR U/ml as an optimum cut-point (sensitivity, 86%; specificity, 89%). The EIA detected antibody more sensitively than a commercially available test. The EIA was transferred to another laboratory, where four operators matched reference laboratory results for a panel of unknowns. Quantitation of antibody to HEV and confirmation of its specificity by Western blotting make HEV serology more meaningful.