Assessing the validity of an ELISA test for the serological diagnosis of human fascioliasis in different epidemiological situations

Objectives To improve the diagnosis of human fascioliasis caused by Fasciola hepatica and Fasciola gigantica, we evaluated the diagnostic accuracy of an enzyme‐linked immunosorbent assay (ELISA), with Fasciola antigen from the adult liver fluke, for the detection of IgG against fascioliasis in human sera. Methods The sera of 54 fascioliasis cases, originating from three endemic areas, were used in this evaluation: (i) a hyperendemic F. hepatica area where humans usually shed a great number of parasite eggs in faeces (11 sera); (ii) an epidemic F. hepatica area where humans usually shed small amounts of parasite eggs (24 sera) and (iii) an overlap area of both Fasciola species and where human shedding of parasite eggs in faeces is usually scarce or non‐existent (19 sera). One hundred and sixty‐eight patients with other parasitic infections and 89 healthy controls were also analysed. Results The respective sensitivity and specificity of this assay were 95.3% (95% confidence intervals, 82.9–99.2%) and 95.7% (95% confidence intervals, 92.3–97.5%). No correlation between egg output and the OD450 values of the F. hepatica IgG ELISA test was observed. Conclusions This test could be used both as an individual serodiagnostic test for human fascioliasis when backed up by a compatible clinical history together with a second diagnostic technique for other cross‐reactive helminth infections, and in large‐scale epidemiological studies of human fascioliasis worldwide.     

Congenital transmission of Trypanosoma cruzi: an operational outline for detecting and treating infected infants in north-western Argentina

We designed a set of procedures for first-line local health services to detect and treat the congenital transmission of Trypanosoma cruzi at a province-wide scale, and field-tested the programme in the province of Tucumán, northwestern Argentina, from 1992 to 1994. The programme consists of routine screening of pregnant women for seroreactivity to T. cruzi, serological and parasitological follow-up of the newborn at least twice during the first year of age, treatment of the infected infants, and evaluation of the outcome. 927 (5.5%) of 16 842 pregnant women were seroreactive to T. cruzi by indirect haemagglutination assay and ELISA. Twenty-one (6.7%) of 315 newborns to seroreactive mothers were diagnosed as infected with T. cruzi parasites microhaematocrit concentration before 30 days of age. Five newborns who initially tested negative had a T. cruzi infection detected by microhaematocrit and/or serological techniques at 3 or 6 months of age. Thus, congenital infection was diagnosed in 26 (7.1%) infants born to seroreactive women and residing in houses free of triatomine bugs. Four of 6 infants born to seroreactive mothers died during the first year of age and had some evidence of T. cruzi infection; one of the deaths was attributed to T. cruzi based on clinical evidence. After specific treatment with nifurtimox or benznidazole, 30 of 32 infants remained parasitologically and serologically negative. This study shows the feasibility of controlling the incidence of congenitally acquired T. cruzi infections at a province-wide scale by means of a specific screening programme at first-line health services level.     

重组抗原在弓形虫病诊断中的应用

刚地弓形虫感染危害严重,研究敏感性高和特异性好的弓形虫感染检测方法对于弓形虫病的诊断至关重要。弓形虫病的诊断一般依赖于检测患者血清中弓形虫特异性IgM和IgG。目前,商业试剂盒大多采用天然抗原,其检测精确性较差。重组抗原已经被发展用来诊断弓形虫病,且具有潜在的应用价值。本综述主要介绍重组抗原在弓形虫病诊断中的应用。     

苄星青霉素联合头孢曲松对早期梅毒血清快速血浆反应素环状卡片试验/甲苯胺红不加热血清试验结果影响的Meta分析

【摘要】 目的 系统评价苄星青霉素联合头孢曲松治疗早期梅毒对血清快速血浆反应素环状卡片试验/甲苯胺红不加热血清试验（RPR/TRUST）转阴率的疗效。方法 检索PubMed、Web of science、Embase、Cochrane、中国知网、万方、维普数据库中关于苄星青霉素联合头孢曲松治疗早期梅毒的病例对照研究。使用Newcastle-Ottawa量表（NOS）评估纳入研究文献的质量,使用RevMan5.3软件分析患者RPR/TRUST转阴率。结果 共纳入14个病例对照研究1 160例梅毒患者,联合组585例,单用组575例。结果显示,联合组血清RPR/TRUST转阴率明显高于单用组［OR = 3.70,95% CI（2.71,5.06）,P < 0.001］。按随访时间进行亚组分析,联合治疗组在治疗后3个月［OR = 3.68,95% CI（2.26,5.98）,P < 0.001］、6个月［OR = 3.11,95% CI（2.26,4.27）,P < 0.001］及12个月时［OR = 4.35,95% CI（2.81,6.73）,P < 0.001］RPR/TRUST转阴率均高于单用组。结论 与苄星青霉素相比,苄星青霉素联合头孢曲松治疗早期梅毒能更有效地促进血清RPR/TRUST转阴。     

免疫酶染色试验和双面胶纸条法环卵沉淀试验诊断血吸虫病的进一步研究

采用免疫酶染色试验(IEST)和双面胶纸条法环卵沉淀试验(DGS—COPT),并以单盲法对比检测153例血吸虫病人,49例经吡喳酮治疗后5年以上的血吸虫病人,22例华支睾吸虫病人和76名健康人的血清。两种方法的敏感性和特异性:IEST 分别为89.5%和89.5%;DGS—COPT 分别为86.3%和97.4%;交叉反应率分别为13.6%和9.1%;已治疗后血吸虫病人的转阴率分别为59.2%和77.6%。两法的经治疗后血吸虫病人未转阴,假阳性及交叉反应者的阳性血清滴度(1∶20—1∶80)或平均环沉率(≥3%)可达所占总数的12.5%—25%或62.7%,这些病例未进行追查,故很难排除其有血吸虫感染的可能性。试验结果进一步证明IEST 及DGS—COPT 均具有较高的诊断和考核疗效的价值。     

梅毒螺旋体抗体的4种血清学检测方法的应用评价

目的：评价酶联免疫吸附试验（ELISA）、梅毒螺旋体抗体胶体金试验、快速血浆反应素试验（RPR）和梅毒螺旋体明胶颗粒凝集试验（TPPA）对梅毒病人诊断的敏感性和特异性。方法：同时用ELISA、胶体金试验、RPR试剂和TPPA对1136例住院及门诊病人血清进行检测，TPPA试验作为确认试验，从而得出其他3种方法的敏感性和特异性。结果：ELISA法的阳性率97．61％（82／84），假阳性率0．28％（3／1052）；金标法阳性率82．14％（69／84），假阳性率5．32％（56／1052）；RPR法阳性率73．8％（62／84），假阳性率0．38％（4／1052）；3种方法即ELISA、金标法、RPR法均阳性为60例，检出率为71．43％（60／84），假阳性率为0．09（1／1052）。在用TPPA方法确认为梅毒螺旋体抗体阳性的血清标本中，金标法和RPR法在弱阳性标本（S／CO值为1～5）的阳性检出率明显低于S／CO值〉5的阳性标本。结论：TP-ELISA法是一种高特异性、高敏感性的梅毒血清学诊断检测方法，TP-ELISA与TPPA相关性良好，可作为确证试验。后两种试验假阴性和假阳性较多，只能作为辅助试验，如果多种方法结合使用，可使假阳性率下降。     

Training medical students in HIV/AIDS test counselling: results of a randomized trial

The study assessed the effectiveness of a programme aimed at increasing medical students' skills in counselling patients presenting for HIV testing/AIDS information. Senior medical students were randomly assigned to receive a short course in pre- and post-test counselling, or to a control group which received the usual curriculum. The students' performance in counselling simulated patients was videotaped at baseline and after 3 months. A subsample was also assessed at 12 months. Students receiving the programme showed significantly greater improvement in pre- and post-test counselling skills over 3 months than did the controls. For the subsample continuing to 12 months, a significant effect over time was found; however, there was no significant difference between the groups. This may have been influenced by the small sample sizes used for the 12-month assessment. General interactional skills improved for the overall sample over 3 and 12 months, but again there were no significant differences between groups. Those exposed to the programme did not show significantly greater changes in either knowledge or attitude scores over either time frame, compared with controls. When taught in addition to the usual undergraduate curriculum at Newcastle University, this short interactional skills course significantly enhanced students' ability to provide pre- or post-test counselling for HIV/AIDS.     

An investigation of the antigenic structure of Toxoplasma gondii

Mechanical fragmentation has been the prime method for preparing soluble Toxoplasma gondii antigens for use in serodiagnosis. The three methods most commonly used (lysis-in-water, sonication and freeze-thawing) all yielded three antigenic peaks (4, 5 and 6) on crossed immunoelectrophoresis. Antigen 6 has been shown to be heat stable (56 degrees C/1 h) and appears to be a major antigen in the indirect haemagglutination test (IHAT). Saponin and octyl glucoside were found to be the most effective detergents for solubilization when used in combination, yielding between 7 and 11 antigens. Using a new triple-staining technique, antigen 3 has been characterized as a glycoprotein, antigen 7 as a lipopolysacchiaride and antigens 1, 2, 4, 5, 6 and 8 to 11 as proteins. Molecular weight determination by gel filtration has been carried out and the majority of the antigens have a mol. wt of 10(5) to 1.5 x 10(5) daltons. Crossed immunoelectrofocusing has shown that all the antigens are isoelectric at acidic pH. The findings of this preliminary investigation into the basic antigenic structure of T. gondii are discussed in relation to future work and the rational development of serodiagnostic tests.     

Schistosoma japonicum: construction of phage display antibody library and its application in the immunodiagnosis of infection

Background A monoclonal antibody would be an effective tool for the detection of circulating antigens in the serum of patients with schistosomiasis, but the traditional way of producing monoclonal antibodies is not cost-effective. The objective of this study was to find a new method for the large-scale production of monoclonal antibodies against Schistosoma japonicum (Sj).Methods A phage display antibody library for Sj was constructed. To obtain a single-chain variable fragment antibody (scFv) against Sj, the library was screened with metabolic antigens from adult Sj worms (Sj-MAg) using enzyme-linked immunosorbent assay. The soluble scFvs selected were used to detect Sj antigens in the serum of acute and chronic schistosomiasis patients.Results Six positive clones with good reactivity to Sj-MAg were obtained from the phage display antibody library of about 1.07 x 106 individual clones. Only two of these six clones bound specifically to Sj-MAg and were chosen for further analysis. Specific soluble anti-Sj-MAg scFvs were produced by inducing the 2 clones with isopropyI-D-thiogalactopyranoside. The characteristics of the scFvs were then determined. The results of Western blot showed that these scFvs could bind to Sj-MAg specifically and had a molecular weight of about 31 kD. When testing serum from schistosomiasis patients with one of the two specific scFvs, its sensitivity was found to be 60% and 37% in acute and chronic patients, respectively, with a specificity of 90%. When the two specific scFvs were combined,their sensitivity was found to be 75% and 57% in acute and chronic patients, respectively, with a specificity of 85%.Conclusions The results indicate that the scFvs are potentially useful for the diagnosis of schistosomiasis. The library construction also provides a useful tool for the further screening of other antibodies for both diagnostic and immunotherapeutic applications and for epitope analysis and vaccine design.