老年患者梅毒螺旋体特异性抗体生物学假阳性结果分析

目的 分析我院老年患者梅毒螺旋体特异性抗体筛查情况,同时探讨其生物学假阳性的原因及临床意义.方法选取2016年1月至2016年12月我院8741例60岁以上老年患者,利用化学发光微粒子免疫检测法(CMIA)检测梅毒螺旋体特异性抗体,梅毒甲苯胺红不加热血清试验(TRUST)检测梅毒螺旋体非特异性抗体,同时采用免疫印迹法(Western Blot)进行梅毒确证.根据老年患者年龄将其分为60～69岁、70～79岁和80岁以上三个年龄组进行统计学分析.结果8741例60岁以上老年患者中有354例患者梅毒螺旋体特异性抗体阳性,60～69岁、70～79岁和80岁以上三个年龄组的梅毒螺旋体特异性抗体阳性率分别为3.42%、6.30%和6.02%,差异具有统计学意义(x2=31.236,P<0.001);同时,60~69岁与70~79岁年龄组比较,差异具有统计学意义(x2=28.932,P<0.001).240例老年患者CMIA筛查梅毒抗体阳性标本经TRUST和Western Blot检测都为阴性,且无临床症状和体征、无相关病史,结果判为假阳性.老年患者梅毒抗体假阳性人群主要分布在60~69岁.但随着老年患者年龄的增加,梅毒螺旋体抗体假阳性率也呈上升趋势,60~69岁、70~79岁和80岁以上三个年龄组的梅毒抗体假阳性率分别64.81%、71.43%和87.50%.老年患者梅毒螺旋体抗体生物学假阳性伴有的其他临床症状及指标异常主要包括癌症(55.36%)、溶栓剂或抗凝剂治疗(35.71%)、糖尿病(28.57%)、肝硬化(25.00%)、严重感染(25.00%)、肾病(17.86%)、自身抗体阳性(16.07%)、手术(14.29%)、肝炎(12.50%)和代谢紊乱(8.93%),各类原因相互影响,梅毒抗体检测假阳性S/CO值最高可达10.29.而梅毒螺旋体特异性抗体真阳性老年患者伴有的其他临床症状及指标异常百分比情况明显低于生物学假阳性患者.结论 对于CMIA梅毒筛查阳性而TRUST检测阴性的老年患者,需进行Western Blot检测并结合临床症状、体征和病史,作出最后诊断.老年患者随着年龄的增高,梅毒抗体的假阳性率也呈上升趋势,需注意癌症、自身免疫病、严重感染、代谢紊乱等可能会导致老年患者梅毒抗体检测生物学假阳性的因素,有助于临床医生分析检测结果并向患者作出合理解释.     

应用MAC-ELISA方法检测呼吸道合胞病毒IgM抗体

建立酶联免疫吸附试验(MAC-ELISA)检测呼吸道合胞(RS)病毒特异性IgM抗体方法,并与中和试验(NT)进行对比。 取35例患毛细支气管炎婴幼儿的急性期及恢复期双份血清共70份标本进行研究。MAC-ELISA测得急性期血清中RS病毒特异性IgM抗体的阳性率为27/35(77.14％),而恢复期血清中和抗体呈≥4倍升高者为23/35(65.71％)。凡NT阳性病例,MAC-ELISA也呈阳性;凡MAC-ELISA阴性病例,NT也呈阴性。另4例NT阴性而MAC-ELISA呈阳性。两者阳性符合率为88.57％。 本研究也观察了IgM抗体与年龄的关系。在6个月龄以前,MAC-ELISA的阳性率远远高于NT。 实验说明采用MAC-ELISA检测RS病毒特异性IgM是可靠的快速诊断方法。     

Evaluation of pooled rapid HIV antibody screening of patients admitted to a San Diego Hospital

Current HIV screening guidelines in the United States recommend expanding the scope of HIV screening to include routine screening in health care settings; however, this will require increased resources. Since testing of pooled samples can decrease costs, the test characteristics of pooled rapid antibody testing were determined and optimal pool sizes were estimated for populations with HIV prevalence ranging from 0.25% to 10%. Based on these results, pooled testing methods were evaluated for screening patients admitted to hospital in San Diego, California. Evaluation of pooled antibody testing on samples collected from individuals with known HIV infection found only a modest reduction in sensitivity. These false negative results were only found among samples with very low optical density readings (<0.125 by the ADVIA Centaur? HIV assay). These readings are considered as HIV negative by the ADVIA Centaur? HIV assay, and therefore likely correspond to samples collected during acute infection. Further evaluation of pooled testing of samples collected from individuals during recent infection, found that mini-pool testing of five samples detected HIV antibody in 86% of samples taken within 60 days of the initial infection and 92% of samples taken within 90 days of the initial infection. Based on estimations of optimal pool sizes for low prevalence populations, it was decided to evaluate mini-pools consisting of 10 samples to screen the study's hospitalized patients. During this evaluation, the HIV prevalence among hospitalized patients was 0.8%, and the 10 sample mini-pool testing had 100% sensitivity and specificity. Additionally, pooled testing resulted in an 84.5% reduction in the number of rapid HIV antibody tests needed, as compared to testing each sample individually. Even when incorporating the increased costs of technician time, mini-pooled tested would have resulted in a net savings of 8760 USD for the 523 samples tested in the study. Taken together, these results indicate that pooled rapid antibody testing may reduce substantially the costs for HIV screening in low prevalence populations without a loss in accuracy.     

Long‐term serological follow‐up of blood donors with an HTLV‐Indeterminate Western Blot: Antibody Profile of Seroconverters and Individuals With False Reactions

The high proportion of indeterminate results of the screening test for human T‐lymphotropic virus (HTLV) infection has been a challenge worldwide. In this study, 60 persons with seroindeterminate results for HTLV were followed until their serological status was defined. At least two independent serological tests (EIA and WB) from sequential samples were performed at an average interval of 4.4 years, totaling 141 serum samples tested. Seroconversion occurred in 12 individuals (reactive by EIA, positive by WB and PCR), and 48 were classified as false reactions (non‐reactive EIA and negative PCR, but indeterminate WB). The seroconverter group had epidemiological features similar to those seen in HTLV‐1 carriers, and the average time of follow‐up for seroconversion was 4 years. In the group with false reactions, the most frequent indeterminate WB pattern in the samples was the presence of p24 alone. This pattern was absent in the seroconverter group, suggesting that p24 alone is an indicator of false reactivity. In contrast, the presence of p19 and p24 seems to be an indicator of true reactivity, since this pattern was frequent (66.7%) among the seroconverters and much less common (10.4% of the first samples) among the individuals with false reactions (P = 0.0001). Thus, HTLV infection may be suspected when reactivity to p19 and p24 is observed. Individuals with an indeterminate WB pattern should be followed‐up and retested. The improvement of the HTLV algorithm screening of blood donors has been necessary to reduce inconclusive results and to avoid unnecessary follow‐up to define the status of infection. J. Med. Virol. 82:1746–1753, 2010. © 2010 Wiley‐Liss, Inc.     

酶联免疫法筛查HIV抗体在艾滋病诊断中的应用价值

目的 对比在艾滋病检验中HIV抗体ELISA法筛查结果与免疫印迹试验结果,探讨HIV抗体筛查在艾滋病诊断中的临床价值.方法 选取2000年1月-2014年1月于海军总医院门诊或住院部术前或输血前患者79 231例,对所有患者抽血,采用EHSA方法对HIV抗体进行初筛检测,将阳性标本进行ELISA复核检测及免疫印迹试验确证,记录各标本复核结果及确证结果,并利用SPSS软件进行对比分析.结果 初筛结果阳性189例,复核结果双阳性186例,初筛与确证结果符合率为96.77％,其中2例经确证为阴性,4例确证结果为不确定.确证为阳性、阴性及不确定的HIV抗体初筛样本结果S/CO值分别为9.9 ～38(17.02 ±3.19)、1～5.8(5.18 ±0.48)、6～9.9(7.94±2.34).1＜S/CO值＜5.9、6＜S/CO值＜9.9及S/CO值＞9.9的样本确证试验阳性符合率分别为33.33％、85.71％,、98.22％.189例初筛阳性样本确诊结果阳性符合率为95.24％,确证试验共出现11条反应带,出现频率由高到低依次为gp160、gp24、gp120、gp41、p66、p51、p31、p17、p55、p39和p36,前4者出现率为95％以上.结论 通过ELISA方法进行HIV抗体筛查阳性率高,但存在一定的假阳性率,其阳性符合率与S/CO值呈正相关性,虽然高S/CO值不能证明其HIV感染,但它是艾滋病诊断中有效的方法.     

Experiences of patients with false positive results from colorectal cancer screening.

A survey was conducted to study the experiences of patients with false positive results for colorectal cancer. The study patients were participants in a randomized trial of compliance with different methods of colorectal cancer screening by faecal occult blood testing. Fifty four out of fifty six patients (96.4%) with false positive results agreed to be interviewed. An age and sex matched control group of 112 patients with negative test results was identified --92 (82.1%) returned questionnaires. Thirteen of the patients with false positive results (24.1%) and 19 controls (20.7%) were to some extent distressed by the initial letter inviting them to participate in the screening programme. Thirty seven of the patients with false positive results (68.5%) felt some degree of distress at the initial positive test result and 19 (35.2%) some distress because of delays experienced in the process of being screened. Ten false positive patients had colonoscopy and the median waiting time for this procedure was 10 days--half of the patients found this wait distressing. Nevertheless, 53 of the patients with false positive results (98.1%) felt that it had been worthwhile to have had the test. Generally, colorectal screening was as acceptable to the patients who experienced false positive results as to those with negative results.     

2012~2018年北京市海淀医院HIV抗体检测结果分析及防控策略

目的通过对北京市海淀医院2012~2018年HIV抗体检测初筛与确认结果数据的分析,了解人类免疫缺陷病毒感染人群的流行病学特点,初筛与确认结果的相关性,为预防及干预其感染制定防治政策提供参考依据。方法以2012~2018年的246458例样本为研究对象,用化学发光法和ELISA法初筛,初筛阳性的样本送确证实验室免疫印迹法(WB)确认。回顾分析阳性患者一般资料,对检测结果进行描述流行病学分析。结果2012~2018年共完成HIV抗体检测246458例,初筛553例阳性标本,阳性率0.22%,确证阳性337例,阳性率0.14%;阴性121例,不确定95例;确证阳性患者年龄在16~76岁之间,其中男性318例,女性19例,男性构成比94.36%,明显高于女性5.64%,年龄分布21~30岁为高危人群,占59.05%,病例分布以皮肤科门诊患者居多,占69.44%。结论艾滋病总体呈散发、低流行,以21~30岁的男性为高危人群,应加强预防和控制措施,建立健全服务体系,加强高危人群的筛查,进行相关知识的宣传,尤其是高校大学生的教育,有效地遏制艾滋病的蔓延。同时提高检测技术以降低HIV抗体检测的假阳性率,对预防和控制其感染具有重要意义。     

Screening of blood donors for human cytomegalovirus (HCMV) IgG antibody with an enzyme immunoassay using recombinant antigens.

BACKGROUND: Screening of blood donors for human cytomegalovirus (HCMV) infection is usually performed by the combined detection of specific IgG and IgM antibody. However, in most of the cases of primary infection HCMV IgG seroconversion is observed concomitantly to IgM production and HCMV IgM antibody detection for blood donor screening is subject to a relatively high frequency of false positive results. OBJECTIVE: In the present study a newly established HCMV IgG ELISA based on recombinant antigens (anti-HCMV recombinant IgG ELISA, Biotest) was evaluated in terms of sensitivity and specificity for blood donor screening. STUDY DESIGN: A total of 442 serum samples including follow-up sera of five patients suffering from primary HCMV infection, selected seropositive and seronegative blood donors and routine specimens were comparatively investigated with three HCMV antibody ELISAs (anti-HCMV recombinant IgG ELISA, Biotest; Enzygnost anti-CMV/IgG + IgM, Dade Behring; and Captia CMV-TA, Centocor). RESULTS: IgG seroconversion was detected with anti-HCMV recombinant IgG ELISA as early as IgM in all five patients suffering from primary infection. The alternative ELISAs were less sensitive, detecting seroconversion one to three bleeds later in 2 (Enzygnost anti-CMV/IgG + IgM) and 4 patients (Captia CMV-TA), respectively. Anti-HCMV recombinant IgG ELISA showed a 99.1% agreement with Enzygnost anti-CMV/IgG + IgM and/or Western blot in the preselected blood donors and routine specimens. Relatively high numbers of false negative (n=20) and positive results (n=7) were obtained with Captia CMV-TA. CONCLUSIONS: Our preliminary data suggest that HCMV antibody screening of blood donors can be performed reliably by detection of specific IgG provided that a highly sensitive assay system is used.     

Evaluation and long-term follow-up of infants with inborn errors of metabolism identified in an expanded screening programme

Newborn screening (NBS) by tandem mass spectrometry started in Galicia (Spain) in 2000. We analyse the results of screening and clinical follow-up of inborn errors of metabolism (IEM) detected during 10 years.Our programme basically includes the disorders recommended by the American College of Medical Genetics. Since 2002, blood and urine samples have been collected from every newborn on the 3rd day of life; before then, samples were collected between the 5th and 8th days. Newborns who show abnormal results are referred to the clinical unit for diagnosis and treatment.In these 10 years, NBS has led directly to the identification of 137 IEM cases (one per 2060 newborns, if 35 cases of benign hyperphenylalaninemia are excluded). In addition, 33 false positive results and 10 cases of transitory elevation of biomarkers were identified (making the positive predictive rate 76.11%), and 4 false negative results. The use of urine samples contributed significantly to IEM detection in 44% of cases. Clinical symptoms appeared before positive screening results in nine patients (6.6%), four of them screened between days 5 and 8. The death rate was 2.92%; of the survivors, 95.5% were asymptomatic after a mean observation period of 54 months, and only two had an intellectual/psychomotor development score less than 85. Compared to other studies, a high incidence of type I glutaric aciduria was detected, one in 35,027 newborns.This report highlights the benefits of urine sample collection during screening, and it is the first study on expanded newborn screening results in Spain.     

TP-光激化学发光、TPPA、TRUST试验的临床应用评价

目的 通过对TP-光激化学发光、梅毒螺旋体明胶颗粒凝集试验（TPPA）、甲苯胺红不加热血清试验（TRUST）的临床应用进行评价,为临床医生在不同情况下选择梅毒螺旋体抗体检测方法提供依据。方法 选取2019年4月1日~7月31日我院11619例住院患者、2458例门诊患者及2983例健康体检者进行TP-光激化学发光和TRUST检测,将TP-光激化学发光检测阳性或TRUST检测阳性的标本进行TPPA法检测,比较TP-光激化学发光及TRUST检测结果,TP-光激化学发光、TRUST检测及TPPA法检测结果及检测梅毒螺旋体抗体的诊断价值,TP-光激化学发光、TRUST检测梅毒螺旋体抗体的诊断价值及TP-光激化学发光法S/CO值与TPPA结果。结果 TP-光激化学发光检测门诊阳性率为6.18%,住院阳性率为3.46%,体检阳性率为0.67%;TRUST检测门诊阳性率为3.42%,住院阳性率为1.11%,体检阳性率0.27%。对557例TP-光激化学发光阳性和222例TRUST检测阳性的标本同时进行TPPA法检测,TPPA法阳性率为79.73%,TP-光激化学发光阳性率为98.30%,TRUST阳性率为37.82%,三种方法检测结果两两比较,差异有统计学意义（P＜0.05）。TRUST检测梅毒螺旋体抗体的敏感度低于TP-光激化学发光,差异有统计学意义（P＜0.05）。以TPPA结果为标准,通过对TP-光激化学发光结果的S/CO值分段分析,结果显示S/CO值越高,与TPPA的阳性符合率越高。结论 TP-光激化学发光灵敏度高,适用于梅毒的感染筛查及辅助诊断;TPPA法检测适用于梅毒感染的确诊,能有效排除TP-光激化学发光和TRUST假阳性的问题;TRUST检测灵敏度较低,对梅毒螺旋体的筛查结果准确性不及TP-光激化学发光和TPPA法检测,不适合用于梅毒感染的筛查,可联和使用TP-光激化学发光以提高诊断梅毒的准确率。     

Screening for urinary tract infection with the Sysmex UF-1000i urine flow cytometer

The diagnosis of urinary tract infection (UTI) by urine culture is time-consuming and can produce up to 60 to 80% negative results. Fast screening methods that can reduce the necessity for urine cultures will have a large impact on overall turnaround time and laboratory economics. We have evaluated the detection of bacteria and leukocytes by a new urine analyzer, the UF-1000i, to identify negative urine samples that can be excluded from urine culture. In total, 1,577 urine samples were analyzed and compared to urine culture. Urine culture showed growth of ≥10(3) CFU/ml in 939 samples (60%). Receiver operating characteristics (ROC) curves and ROC decision plots were been prepared at three different gold standard definitions of a negative urine culture: no growth, growth of bacteria at <10(4) CFU/ml, and growth of bacteria at <10(5) CFU/ml. Also, the reduction in urine cultures and the percentage of false negatives were calculated. At the most stringent gold standard definition of no growth, a chosen sensitivity of 95% resulted in a cutoff value of 26 bacteria/μl, a specificity of 43% and a reduction in urine cultures of only 20%, of which 14% were false negatives. However, at a gold standard definition of <10(5) CFU/ml and a sensitivity of 95%, the UF-1000i cutoff value was 230 bacteria/μl, the specificity was 80%, and the reduction in urine cultures was 52%, of which 0.3% were false negatives. The applicability of the UF-1000i to screen for negative urine samples strongly depends on population characteristics and the definition of a negative urine culture. In our setting, however, the low workload savings and the high percentage of false-negative results do not warrant the UF-1000i to be used as a screening analyzer.     

Validation of pncA gene sequencing in combination with the mycobacterial growth indicator tube method to test susceptibility of Mycobacterium tuberculosis to pyrazinamide

Pyrazinamide is important in the treatment of tuberculosis. Unfortunately, the diagnosis of pyrazinamide resistance is hampered by technical difficulties. We hypothesized that mutation analysis combined with the mycobacterial growth indicator tube (MGIT) phenotypic method would be a good predictor of pyrazinamide resistance. We prospectively analyzed 1,650 M. tuberculosis isolates referred to our tuberculosis reference laboratory in 2008 and 2009. In our laboratory, the MGIT 960 system was used for pyrazinamide resistance screening. If a pyrazinamide-resistant strain was detected, we performed a pncA gene mutation analysis. A second MGIT 960 susceptibility assay was performed afterwards to evaluate the accuracy of the pncA mutation analysis to detect true- or false-positive MGIT results. We observed pyrazinamide resistance in 69 samples using the first MGIT 960 analysis. In a second MGIT 960 analysis, 47 of the 69 samples proved susceptible (68% false positivity). Sensitivity of nonsynonymous pncA mutations for detecting resistant isolates was 73% (95% confidence interval [CI], 61% to 73%), and specificity was 100% (95% CI, 95% to 100%). A diagnostic algorithm incorporating phenotypic and molecular methods would have a 100% positive predictive value for detecting pyrazinamide-resistant isolates, indicating that such an algorithm, based on both methods, is a good predictor for pyrazinamide resistance in routine diagnostics.     

Chlamydia pneumoniae and screening for tubal factor subfertility

Chlamydia antibody testing (CAT) by micro-immunofluorescence (MIF) tests has been introduced into the fertility work-up as a screening test for tubal factor subfertility. In this study the role of C. pneumoniae antibodies, as a cause for false positive CAT results due to cross-reactivity with C. trachomatis antibodies in the MIF test, has been evaluated. In 240 subfertile women serological data were compared to laparoscopy findings. The prevalence of C. pneumoniae antibodies using enzyme-linked immunosorbent assay (ELISA) was 75% and did not differ between patients with and without tubal pathology. C. pneumoniae antibodies were found in 87% of women with a positive MIF test (> or =32), and in 66% with a negative MIF test (P < 0.0005). Using ELISA instead of MIF for the detection of C. trachomatis antibodies, C. pneumoniae antibodies were found in 87% of C. trachomatis positive women, and in 69% of C. trachomatis negative women (P < 0.0005). Patients without tubal factor subfertility but a positive MIF test showed C. pneumoniae antibodies more frequently than patients without tubal factor subfertility and a negative MIF test. Therefore it was suggested that C. pneumoniae antibodies may be the cause of false positive CAT results. Remarkably, tubal pathology was more common in patients who had antibodies to both C. trachomatis and C. pneumoniae.     

Comparison of different methods for anti-HTLV-I assay]

In 130 patients, who were considered to be anti-HTLV-I positive or negative by the PA method, we compared the anti-HTLV-I detection rates and the specificity of the following three EIA methods: the Ei-test ATL and two new EIA methods using different recombinant antigens which recognize different sites. The results from the three EIA methods were consistent with the results from the PA method at a rate over 96.9%. The specificity and sensitivity of the three methods were excellent. In 8 (0.6%) of the 130 cases, however, the results from the four methods were not in agreement. All of these 8 cases had been classified (by the PA method) as weakly positive (low antibody titer). The use of the Ei-test ATL produced some false positive cases and some false negative cases (no false negative cases have been reported in tests for anti-HTLV-I antibody before). In 3 patients, the results of the two new EIA methods were not in agreement. Because all of these three patients had a low antibody titer, the discrepancy was difficult to explain based on the difference in the antigens used. Although the four methods had similar anti-HTLV-I detection rates, the results indicate a need to carefully evaluate the data in patients with low antibody titers. Therefore, it is recommended that a combination of multiple tests be used or that the results from one test be checked against those from another test.     

高效表达重组HIV-1 gp41及在尿液检测中的应用

目的 应用优化的HIV-1 gp41基因,通过原核表达得到高纯度的重组HIV-1 gp41抗原,制备基于重组gp41抗原的尿液HIV-1抗体检测试剂盒,并评价此试剂盒在尿液抗体检测中的灵敏度和特异性.方法 将编码HIV-1B亚型gp41主要抗原表位的基因插入到原核表达载体pET22b中,构建表达质粒pET22b-mgp41.将表达质粒转化B121(DE3)后经IPTG诱导其表达重组抗原rgp41.重组抗原经镍离子亲和层析和分子筛层析得到纯化.将纯化后重组抗原包被ELISA板,对4796份正常人群尿液、641份HIV-1抗体阳件感染者尿液进行HIV-1抗体检测.结果重组抗原经纯化后纯度95%.用本实验中制备的HIV-1抗体尿液检测试剂盒的检测结果显示,此试剂盒灵敏度为100%,特异性为98.52%.结论 本研究中制备的HIV-1尿液诊断试剂盒可以满足HIV感染者初筛实验的需要.     

Immunoblot in the serological diagnosis of hepatitis C virus infection

The objective of the study was to assess three immunoblot assays, the Deciscan HCV Plus, the Riba and the Inno-Lia, on 44 discordant samples with three EIA kits. These immunoblots were considered as confirmation reagents. A result was considered as a false positive by anti-HCV antibody assay if the three immunoblots were negative or if two immunoblots were negative with the third being indeterminate and a negative virological genomic diagnosis observed on all the samples. The result was positive if at least two immunoblots out of three were positive. Thus, 34 samples were considered as false positive and ten samples were excluded because it was impossible to conclude between true or false positive result. The 44 discordant results were never confirmed as positive by the use immunoblot or PCR. The three immunoblots were negative for half of the samples and two immunoblots and one indeterminate were observed for 77% of the samples. The false positive results by the Monolisa assay were more often found indeterminate with the Deciscan assay than with the other immunoblots. That was also checked for Vitros/Riba pair. One of the explanations could be the use of common antigens for the reagents from the same manufacturer. The Inno-Lia test is the most specific immunoblot according to the results obtained in our study.     

Usefulness of the hepatitis C virus core antigen assay for screening of a population undergoing routine medical checkup

We studied the usefulness of the recently designed Trak-C assay for the detection and quantification of the hepatitis C virus (HCV) core antigen (Ag) for the screening of HCV infection in 4,201 subjects selected from 74,150 consecutive volunteers undergoing routine medical checkups. Subjects were selected for screening because they had risk factors (group II, n = 321) and/or elevated alanine transaminase activity (group I, n = 3847). Initially, the anti-HCV antibody assay and the Trak-C assay were performed on each patient. Subsequently, the Trak-C assay was performed only when the anti-HCV enzyme immune assay (EIA) was positive. Positive samples were further evaluated for anti-HCV antibodies by a third-generation strip immunoblot assay and for HCV RNA. Four samples (1.2%) from group II and 113 (2.9%) from group I were anti-HCV EIA positive. We also tested 33 subjects who previously tested positive for anti-HCV in our medical center. Among the 150 anti-HCV EIA-positive samples, the HCV core Ag result was in accord with the HCV RNA result in 146 cases (97.3%). When the EIA result was positive, the HCV core Ag concentration and the HCV RNA load were correlated (r(2) = 0.78; P < 0.001). Four samples with low viral loads were Trak-C negative but HCV RNA positive. Among the 2,395 anti-HCV EIA-negative serum samples collected during the first part of the study, 17 (0.7%) were found to contain very low levels of HCV core Ag (<8.5 pg/ml, the cutoff value being 1.5 pg/ml). All these samples were HCV RNA negative and considered to be false positives. This was confirmed by HCV core Ag neutralization analysis. The HCV core Ag assay is a useful method in the screening strategy of HCV infection and provides a reliable means of distinguishing between current and cleared HCV infections that is well correlated with HCV RNA testing.     

Evaluation of the Coulter STKR differential histogram and the Coulter VCS formula analysis: a strategy of joint utilization

Coulter STKR is an haematological analyser providing a histogram differential analysis with interpretative report (IR). Coulter VCS is a flow cytometer providing a leucocyte five-part differential. Both instruments include a software for flagging abnormal differentials. They were evaluated in an hospital with numerous haematological and Pediatric patients. By using the same criteria as the analysers, the frequency of abnormalities found in 638 samples by the optical method was 42%. STKR histogram differential, with IR and monocytes lab action limits, resulted in a 53% review rate with a false negative percentage of 2.2%. VCS analysis resulted in a 52% review rate with a false negative percentage of 0.8%. Association of both instruments, the VCS analysis being performed only on samples having given non IR alarms, resulted in a lower false negative percentage (0.5%). In a population such as ours, with an important part of pathological conditions, these results may be considered satisfactory, both regarding the safety and the review rate.     

Frequent false positive beta human chorionic gonadotropin tests in immunoglobulin A deficiency

A patient with IgA deficiency had a series of positive serum pregnancy tests which led to medical and surgical procedures for suspected molar pregnancy. These tests were found to be falsely positive due to heterophile antibody. The aim of this study was to determine the frequency of false positive betahCG assays in sera of IgA deficient patients. Sera from a panel of IgA deficient (IgA < 7 mg/dl) patients were tested for the presence of betaHCG using three different assays, and also for IgG anti-goat and anti-mouse antibodies. Patients were seen at Mount Sinai Medical Center and included 54 patients (ages 1-80 years, 32 females, 22 males) with IgA deficiency. Thirty percent of 54 IgA deficient patient sera yielded positive pregnancy tests by one or more of the three betahCG assays, however, none of the patients were pregnant. In comparison to sera of normal controls, 39% of the patient sera contained significant amounts of anti-goat antibody and 18% contained significant amounts of anti-mouse antibody. While heterophile antibodies are common in IgA deficient serum, false positive assays for betahCG in IgA deficient serum have not been previously reported. The possibility of false positive test results should be considered prior to invasive procedures in IgA deficient patients.