巴楚县2001年新疆出血热疫情的血清学证实

目的：以血清流行病学方法调查新闻出血热（XHF）病人，易感人群和主要宿主动物中疾病的感染情况。方法：分别收集2001年4－6月新疆巴县临床诊断为XHF的病人血清，易感人群血清和主要宿主动物的血清，用研制的诊断试剂以酶联免疫吸附试验（ELISA）检测XHF特异性IgG和IgM抗体；用抗原捕获ELISA检测XHF病毒抗原。结果：病人血清IgG抗体阳性率为39．62％（21／53）。IgM抗体阳性率为20．75％（11／53），抗原获ELISA有1份血清为XHF抗原阳性；易感人群血清IgG抗体阳性主为21．05％（4／19），IgM抗体检测和抗原捕获ELISA全部为阴性；羊血清IgG抗体阳性率为70％（56／80）。结论：血清流行病学研究证实该次疫情确系XHF、流行地区人畜均有较高水平的隐性感染。     

Serological response of chickens to Salmonella enteritidis infection

Fifty-eight sera, from 29 chickens originating from two layer flocks known to be naturally infected with Salmonella enteritidis phage type (PT) 4, were examined for antibodies to S. enteritidis. Using the techniques of immunoblotting and ELISA, antibodies to the lipopolysaccharide (LPS) of S. enteritidis were detected in 43 of 58 sera. Antibodies were of the IgG class and bound to the S. enteritidis LPS antigen O = 12. Bacterial agglutination reactions using whole-cell preparations of S. enteritidis and S. pullorum, correlated with anti-LPS antibody reactions as detected by immunoblotting and ELISA. A rapid means of screening chicken sera for antibodies to the LPS of S. enteritidis as an indicator of infection is discussed.     

Antigenic relationships between the typhus and spotted fever groups of rickettsiae.

Paired sera from cases of epidemic typhus in Ethiopia and from probable cases of Rocky Mountain spotted fever (RMSF) in the United States were examined by microagglutination (MA) and microimmunofluorescence (micro-IF) tests for antibodies against Rickettsia prowazekii, Rickettsia typhi, Rickettsia canada, Rickettsia rickettsii, Rickettsia conorii and Ricksettsia akari. IgG and IgM antibodies against the various rickettsiae were titrated with specific fluorescein-conjugated anti-IgG and anti-IgM sera. Purified, particulate rickettsial antigens were employed in all tests. A majority of patients acutely ill with epidemic typhus produced both IgG and IgM antibodies against R. prowazekii, R. typhi and R. canada. Concurrently they produced IgG (but seldom IgM) antibodies against members of the spotted fever group. In contrast, patients ill with probably spotted fever, while producing IgG and IgM antibodies against R. rickettsii, R. conorii and R. akari, also produced both IgG and IgM antibodies with about equal frequency against members of the typhus group. It was concluded that a relatively broad antigenic relationship exists between rickettsiae of the typhus and spotted fever groups.     

SARS-CoV特异性抗体产生规律的初步研究

目的 研究严重急性呼吸综合征(SARS)患者感染后体内病毒特异性抗体产生规律。方法 收集临床确诊为SARS患者的血清和非SARS人群血清标本,用IgM捕获法、间接法和抗原夹心法三种不同方法检测抗SARS病毒特异性IgM、IgG和总抗体。结果 检测146份临床诊断为SARS的患者不同发病时间血清标本,三种抗体阳性率分别为61.64％、53.43％和69.86％;SARS病毒特异性IgM、IgG抗体的最早检出时间分别在发病第7天和第12天,特异性IgM抗体最短在发病后42天消失。三种方法检测70份甲型肝炎患者血清时,均有2份非特异阳性反应,检测127份其他病种血清均阴性,1例密切接触SARS患者的医务人员SARS特异性IgG抗体和总抗体均阳性,三种检测方法均不受类风湿因子影响。结论 与其他病毒感染相比,SARS病毒感染者的特异性IgM抗体检出时间较晚,且持续时间较短;三种检测方法均有较好的特异性和敏感性,可用于SARS的流行病学调查和临床诊断的确认和补充,但不适用于SARS的早期诊断。     

新型冠状病毒肺炎病例的血清学检测结果初步分析

目的 了解新型冠状病毒肺炎确诊病例、无症状感染者、密切接触者和其他相关人员血清中IgM和IgG抗体产生情况。 方法 采集研究对象的全血并及时分离血清,采用ELISA和胶体金法对确诊病例和无症状感染者血清进行IgM和IgG抗体检测,采用ELISA对密切接触者和其他相关人员血清进行检测。 结果 用ELISA和胶体金法进行抗体检测,42例确诊病例的阳性情况为:采样日期从第二周起,不论是IgM还是IgG的阳性率均出现增长,第15~35 d组,阳性率最高,IgM抗体阳性率ELISA和胶体金法分别为72.7%与36.4%,IgG抗体阳性率分别为72.7%与90.9%。用ELISA检测,8例无症状感染者为IgM阳性5例(62.5%)和IgG阳性5例(62.5%)。密切接触者为IgM阳性1例(1.7%)和IgG阳性2例(3.4%)。其他相关人员为IgM阳性1例(2.0%)和IgG阳性2例(4.1%)。ELISA IgM、胶体金IgM、ELISA IgG以及胶体金IgG试验检测出阳性确诊病例的发病日期至采样日期的间隔时间中位数分别为16、14、12、13 d。ELISA与胶体金法比对,IgM抗体检测的Kappa值为0.614,IgG的Kappa值为0.716。 结论 新型冠状病毒肺炎确诊病例血清抗体阳性率从第二周起出现显著增长,不同类型人员阳性率差异有统计学意义,ELISA与胶体金法比较中高度一致。     

463例疑似登革热病例实验室监测结果分析

目的 对463例疑似登革热病例开展血清学和病原学监测,了解NS1抗原、IgM/IgG抗体及病毒核酸在不同病程的产生规律。 方法 对疑似登革热病例血清应用胶体金免疫层析法(gold immunochromatographic assay, GICA)和荧光免疫层析法(fluorescence immunochromatography assay,FICA)检测NS1抗原,比较两种方法的特异性和敏感性。用GICA检测IgM和IgG抗体,分析不同病程抗体产生规律。用Real-time RT PCR检测病毒核酸,了解不同病程核酸检测阳性的时间分布。 结果 463例疑似登革热病例实验室确诊353例。353例病例在发病的0~3 d内以核酸的检出率最高,达97.08%(133/137);其次是NS1抗原,检出率为91.97%(126/137);在发病的8~14 d内NS1抗原和IgM抗体的检出率最高,检出率均为78.94%(45/57);病程≥15 d NS1抗原、IgM抗体、IgG抗体、核酸的检出率分别为58.06%(18/31)、61.29%(19/31)、54.84%(17/31)、87.10%(27/31);GICA与FICA检测NS1抗原的阳性符合率、阴性符合率、总符合率分别为94.88%(278/293)、85.00%(51/60)、93.20%(329/353),kappa值为0.768,具有较好的一致性。 结论 登革病毒NS1抗原和核酸在感染早期具有较高的检出率和一致性;IgM/IgG抗体随病程延长检出率增高,在发病的第二周后检出率最高;GICA与FICA检测NS1抗原均适合基层早期诊断与筛查。     

Production and Evaluation of Toxoplasma gondii Recombinant Surface Antigen 1 (SAG1) for Serodiagnosis of Acute and Chronic Toxoplasma Infection in Human Sera

Background

The assays currently available for the detection of specific anti-Toxoplasma antibodies may vary in their abilities to detect serum immunoglobulins, due to the Lack of a purified standardized antigen. The aim of this study was evaluation the recombinant Toxoplasma gondii SAG1 antigen for the serodiagnosis of acute and chronic toxoplasmosis.

Methods

This study describes an ELISA using recombinant SAG1 for detection of IgM and IgG antibodies against Toxoplasma gondii in human sera. Genomic DNA of T. gondii (RH Strain) was isolated and PCR reaction was performed. Recovered DNA was cloned into PTZ57R cloning vector. The recombinant plasmid was detected by restriction analysis. The SAG1 gene was subcloned in the pET- 28a expression vector. Protein production was then induced with 1 mM isopropyl-D – thiogalactopyranoside (IPTG). A total of 204 sera were tested using a commercial IgG and IgM ELISA kit (Trinity, USA) as gold standard prior to testing them with the recombinant antigen.

Results

Tested sera were divided into the following groups:(a) The 74 T. gondii IgG positive (b) 70 T.gondii IgM positive (c) 60 sera who had no serological evidence of toxoplasmosis as negative sera.To determine the specificity of the test, we used other parasitic diseases including echinococusis (N=5), malaria (N=14), leishmaniasis (N=7),fasciolasis (N=4), sterengyloidiasis (N=1). Sensitivity and specificity of the generated recombinant IgG ELISA in comparison with commercial ELISA (Com ELISA) were 93% and 95%, and the sensitivity and specificity of the generated recombinant IgM ELISA were 87% and 95% respectively.

Conclusion

The results acquired here show that this antigen is useful for diagnostic purposes and could be replaced by lysed, whole cell antigens for diagnosis of chronic toxoplasmosis.     

Assessment of Brucellosis Card test in screening patients for brucellosis

The Brucellosis Card test (Brewers' Diagnostic Kits, Hynson, Westcott and Dunning, Inc., Baltimore, Md.) was evaluated in relation to the Brucelloslide test (bioMérieux, France), the microagglutination test (MAT) and the demonstration of brucella-specific IgG, IgM and IgA in an enzyme-linked immunosorbent assay (ELISA). A total of 573 serum specimens was tested. These included sera from patients with acute brucellosis (159), chronic brucellosis (23) and patients who had been diagnosed previously as having had brucella infection (155). Control groups consisted of patients with diseases other than brucellosis (52), others with non-infectious diseases (20), and healthy individuals (164). The Card test detected 100% of the patients with acute and 61% of the patients with chronic brucellosis. The sera from the control groups were all negative. Similar results were obtained with the Brucelloslide test and the MAT. The ELISA test detected brucella-specific Ig of all classes in the serum of patients with acute brucellosis, and IgG and IgA in the serum of patients with chronic brucellosis. In the latter group, IgM was also detected in 32% of the sera. Twenty-three per cent of sera with titres of 20 by the MAT were positive on the Card test and had ELISA titres for IgM, IgG and IgA of 400. Characterization of the antibodies involved in the Card test showed that sera with IgM ELISA titres of 1600, or an IgM titres of 800 together with IgG and IgA titres greater than or equal to 200 were Card test positive. Higher IgG (greater than or equal to 1600] plus IgA (greater than or equal to 400) titres were required to produce a positive Card test in the absence of IgM or when the IgM titre was less than or equal to 200. The Card test has a potential value as a rapid screening test for humans with acute brucellosis and shows similar results to Brucelloslide and MAT tests. ELISA, however, remains the most reliable test for diagnosis of brucellosis especially in patients with chronic and complicated stages of the disease.     

A study on the usefulness of counter immuno-electrophoresis for the detection of Salmonella typhi antigen in the sera of suspected cases of enteric fever

Counter immuno-electrophoresis (CIE) was used to detect the presence of Salmonella typhi antigen and antibodies in the sera of 123 suspected cases of enteric fever. Of these, 68 had been incompletely treated with various antibiotics before establishing the diagnosis. The sera of 31 (25%) of the 123 cases showed the presence of S. typhi antigen. Blood culture was positive for S. typhi in only one case. Antigen could be demonstrated in sera of patients with fever ranging from two to ten days. Antigen could also be demonstrated after ten days in sera of patients who had taken some antibiotics. There is no apparent relationship between the presence of antigen and antibodies in the sera, and no apparent relationship between the CIE antibody and Widal antibody titres.     

肠出血性大肠埃希菌O157：H7引起的溶血性尿毒综合征患者血清抗体调查

目的 对1999年某地出现的一批先有腹泻病症状后继发急性肾功能衰竭（肾衰）的患者进行血清学调查和诊断。方法 使用基因克隆表达纯化的肠出血性大肠埃希菌（EHEC）-溶血素（Hly)和EHECO157脂多糖（LPS）为抗原，对采集自42例肾衰患者的血清标本进行蛋白印记试验。结果 EHEC-Hly的检测发现，IgG抗体阳性21份，阳性率50.0%；IgM抗体阳性16份，阳性率38.1%；在11份标本中同时检测到IgG和IgM抗体，阳性率26.2%；检测到IgG或IgM抗体阳性的标本26份，阳性率61.9%，EHECO157LPS的检测发现，24份标本分别检测到IgG和IgM抗体，阳性率各为57.1%；在29份标本中检测到IgG或IgM抗体，阳性率69.0%;在20份标本中检测到IgG和IgM抗体，阳性率47.6%，在42份血清标本中同时检测到EHEC-Hly和O157LPS的特异性抗体的标本22份，阳性率52.4%；检测到EHEC-Hly或O157LPS的特异性抗体的标本34份，阳性率81.0%。结论 结合细菌学和血清学诊断结果，临床症状和流行病学分析。可以认为这些患者感染了EHECO157：H7，在分离不到病原菌的情况下，检测患者血清标本的EHEC-Hly和/或EHECO157LPS的特异性抗体，不失为一种可以考虑的诊断方法。     

Prevalence of antibodies against hantaviruses among the adult population of the Czech Republic

At least three hantavirus genospecies are circulating among wild rodents in Europe: Puumala, Dobrava and Tula, the two first being of clinical significance for humans as possible causative agents of haemorrhagic fever with renal syndrome. As many as 710 adult individuals randomly selected from 12 regions of the Czech Republic were screened for the presence of antibodies against hantaviruses. Commercial sets with Hantaan and Puumala antigens were used for this purpose. Five subjects showed IgG reactivity to Hantaan-like virus (Dobrava) and one subject tested positive for both IgG and IgM antibodies. Two other subjects showed IgM reactivity alone. This means that as many as seven (1.0%) subjects showed reactivity to Hantaan antigen. Eight subjects showed IgG reactivity to Puumala antigen, none of them being IgM positive. Two other subjects were IgM positive only. Altogether ten (1.4%) subjects were reactive to Puumala antigen. Three subjects showed reactivity to both of the antigens tested.     

Oral fluids for the immunodiagnosis of Schistosoma mansoni infection

Saliva and oral transudate were evaluated for their potential as human specimens in the detection of IgG antibodies against soluble Schistosoma mansoni egg antigen (SEA). Preliminary laboratory testing of 49 subjects, 37 with parasitological proven infection and 12 negative controls, displayed 100% sensitivity in ELISA using serum and oral transudate and 94.6% using saliva. The specificity of the ELISA with serum was 100% versus 91.7% with both oral fluids. Significant Spearman rank correlations of anti-SEA IgG levels with egg counts were observed for serum, oral transudate and saliva (P < 0.05). The sensitivity of dot-ELISA was 100% for serum, 89% for transudate and 81% for saliva, and specificity was 100% for all 3 samples. The immunodiagnostic value of ELISA for the detection of anti-SEA IgG antibodies in oral transudate was further evaluated in 197 individuals from an endemic area of Brazil. The ELISA using serum and oral transudate showed sensitivities of 98.8% and 100% respectively and specificities of 67.8% and 64.3% respectively. Use of oral fluids for the diagnosis of S. mansoni infection was equivalent to sera with respect to test efficacy, offering an alternative to blood collection.     

Application of the Microagglutination Test for Serologic Diagnosis of Human Brucellosis

ObjectivesBrucellosis is one of the most common zoonoses in the world, and occurs mainly in farmers, slaughterhouse workers, and veterinarians via direct or indirect contact with infected animals or their products. The clinical symptoms of human brucellosis are nonspecific, such as fever, headache, chills, and sweating. Diagnosis and treatment of brucellosis requires laboratory tests. Although the serum tube agglutination test (SAT) is the standardized gold method, it is laborious, time consuming, and requires a number of reagents. A microagglutination test (MAT) variant of the SAT or enzyme-linked immunosorbent assay (ELISA) is recommended for serological diagnoses. For the simple and rapid diagnosis of brucellosis, the MAT was standardized using samples for the SAT to define positive and negative categories, and we then compared the sensitivity and specificity of the MAT and ELISA.MethodsThirty SAT-positive sera and 60 SAT-negative sera were used in this study. Antibody titers of ≥1:160 were considered positive readings in both the SAT and MAT. Brucella abortus antigens and Brucella-positive control antiserum were used in the SAT and MAT. ELISAs of IgM and IgG were performed according to the manufacturers’ instructions.ResultsThe titers of the MAT differed according to antigen concentration. The optimal concentration of B abortus antigen was determined to compare the sensitivity and specificity between the MAT and SAT. The sensitivity and specificity of the MAT were 93.3% and 96.7%, respectively, for IgG with reference to ELISA, and 96.7% and 98.3%, respectively, for IgM.ConclusionsThe optimal concentration of antigen for the MAT was 1:10. The MAT is less time consuming and requires less antigen and serum than the SAT. The results of the MAT showed good agreement with those of ELISA. The results of this study suggest that the MAT could be useful for diagnosis of brucellosis.     

Diagnostic performance indices for immunofluorescent tests and enzyme immunoassays of leishmaniasis sera from northern and north-eastern Brazil

A total of 341 sera were screened for anti-Leishmania IgA, IgG, and IgM antibodies by immunofluorescent (IF) tests and enzyme immunoassay (ELISA). Altogether, 292 of the sera originated from patients with clinically as well as parasitologically diagnosed (positive lesion imprint or the Montenegro skin test) cutaneous leishmaniasis; 49 of the sera were from controls from the same base population. In terms of diagnostic performance, the ELISAs for IgG and IgM yielded indices of diagnostic utility, and the positive predictive value for the IgG-ELISA was 94.6%. A remarkably high specificity (100%) was obtained with the IgA-IF test, but its sensitivity was very low.     

Evaluation of a synthetic tripeptide as antigen for detection of IgM and IgG antibodies to Trypanosoma cruzi in serum samples from patients with Chagas disease or viral diseases

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect IgG and IgM antibodies in human sera against a synthetic tripeptide derived from a hybrid peptide containing 3 specific epitopes from Trypanosoma cruzi. This assay was compared in Brazil with one using conventional antigen, the alkaline crude extract. Serum samples were divided into positive (40 samples) or negative (107 samples) for Chagas disease. Positive samples included 9 serum samples from patients with acute Chagas disease, while negative samples included 57 samples from patients suffering from viral diseases. The total percentages of IgG positive samples from patients with chronic Chagas disease for alkaline extract and synthetic tripeptide were 93.5% and 100%, respectively. All samples from patients with acute Chagas disease were confirmed positive for IgM antibodies by using both the tripeptide and the alkaline extract. However, the results for anti-T. cruzi IgM in the group of chronic Chagas disease patients demonstrated that 41.9% were positive for IgM with the alkaline extract, while the synthetic peptide showed a significantly lower number of positive samples (12.9%). The serum samples from healthy people showed similar results for both antigens. However, 40% of the serum samples from patients presenting with viral diseases were IgM positive for Chagas disease when assayed with conventional antigen; with the synthetic tripeptide as antigen, 100% of this group of samples were found to be negative. Thus, as the results of ELISA with synthetic tripeptide showed higher rates of sensitivity and specificity than ELISA with conventional antigen, the former should be included as a laboratory tool in the serodiagnosis of Chagas disease.     

A recombinant antigen-based IgG4 ELISA for the specific and sensitive detection of Brugia malayi infection

An IgG4 ELISA based on a novel recombinant antigen was evaluated for detection of Brugia malayi infection, using 2487 sera from various institutions: 2031 samples from Universiti Sains Malaysia, 276 blinded sera from 2 other institutions in Malaysia, 140 blinded sera from India and 40 blinded sera from Thailand. These sera were from various groups of individuals, i.e., microfilaraemics, chronic patients, endemic normals, non-endemic normals and individuals with other parasitic and bacterial infections. Based on a cut-off optical density reading of 0.300, the IgG4 ELISA demonstrated specificity rates of 95.6-100%, sensitivity rates of 96-100%, positive predictive values of 75-100% and negative predictive values of 98.9-100%. These evaluation studies demonstrated the high specificity and sensitivity of this test for the detection of active B. malayi infection. Thus, the IgG4 ELISA would be very useful as a tool in diagnosis and in elimination programmes for brugian filariasis.     

Evaluation of serological tests using A60 antigen for diagnosis of tuberculosis

Identification of acid-fast bacilli (AFB) in sputum or tissue samples is among definite diagnostic methods of tuberculosis. However, this method of diagnosis is restricted by certain limitations. Serologic diagnosis of tuberculosis (TB) has been used for a long time. The aim of this study was to determine the sensitivity and, specificity of Antigen 60 (A60) IgG, IgA, IgM test results in TB diagnosis. Mycobacterial A60-based ELISA was used to measure specific IgA, IgM and IgG antibodies in the sera of 127 adult TB patients (consisted of 74 pulmonary and 53 extra-pulmonary cases), and 95 controls (46 healthy volunteers and 49 patients with various acute or chronic diseases other than tuberculosis). Data from A60 IgG-based ELISA, chest radiography, AFB culture and pathologic evaluation for AFB were obtained .The cutoff value of A60 IgG, IgA and IgM were chosen according to a receiver operating characteristic (ROC) analysis. The sensitivity, specificity and positive likelihood ratio were determined. The mean levels of IgG, IgA and IgM were significantly higher in patients with pulmonary tuberculosis when compared with control groups. Sensitivity of IgG test was 54.3 %, while the specificity was 84.2%. The IgA test showed a sensitivity of 70.1% with a specificity of 80 %. Combination of the IgG and IgA tests showed a total sensitivity of 45.7 % and a specificity of 94.7% and the positive likelihood ratio of 8.62. Chosen cutoff values of IgG, IgA, and IgM sets were 285,265 and 0.9 ELISA units respectively. Our study results showed a good specificity (94.7%) and a reasonable positive likelihood ratio (8.62) of the test when combined IgA and IgG with new cutoff points were considered on diagnosis of tuberculosis in adult patients. Combined use of both IgG and IgA tests results allows an increased accuracy in diagnostic of tuberculosis.     

Application and evaluation of enzyme-linked immunosorbent assay and immunoblotting for detection of antibodies to Treponema hyodysenteriae in swine

An enzyme-linked immunoassay (ELISA) has been developed to detect serum Immunoglobulin antibodies G and M to Treponema hyodysenteriae in vaccinated, experimentally infected and naturally infected swine. Naturally infected swine gave ELISA titres that were similar to experimentally infected swine, but were significantly less than the titres of vaccinated swine. When serum from naturally infected swine was used to probe nitrocellulose blots of sodium dodecyl sulphate-polyacrylamide gel electrophoresed whole cell proteins of T. hyodysenteriae, the immunoblotting patterns showed IgG antibodies were produced against many T. hyodysenteriae protein antigens and against lipopolysaccharide (LPS). The IgG antibodies directed against LPS were serotype-specific for that LPS and could be used to identify the serotype involved in the T. hyodysenteriae infection in that herd. IgM immunoblots also reacted with the many protein antigens but were less specific for LPS antigen, with a substantial degree of cross-reaction between the LPS of all serotypes. The data demonstrate that a microplate enzyme-linked immunosorbent assay, coupled with immunoblotting, is a very specific and sensitive test for detection of antibody to Treponema hyodysenteriae in swine.     

发热患者SARS冠状病毒抗体分析

目的了解临床发热患者中是否存在严重急性呼吸综合征（SARS）冠状病毒（SARS-CoV）隐性感染或亚临床感染。方法对2003年5月～7月，SARS流行期间湖北地区临床发热患者373例血清进行SARS冠状病毒（SARS-CoV）抗体（IgG、IgM、N蛋白抗体）酶联免疫吸附法（ELISA）检测和分子生物学（RT—PCR）检测。结果373例发热患者中，检出冠状病毒抗体阳性者24例，阳性率6．43％（24／373），其中SARSIgG抗体、IgM抗体、N蛋白抗体阳性率分别为0．54％，1．34％和5．09％，但SARS-CoVRT—PCR检测均为阴性。结论临床发热患者可能存在SARS-CoV隐性或亚临床感染，患者体内产生针对SARS-CoV的保护性抗体，应具有免疫力和抵抗力。     

Quality control of the serological diagnosis of dengue in laboratories throughout the Americas, 1996-2001]

OBJECTIVE: To report the results from participating laboratories for four external quality control proficiency tests of dengue serological diagnosis that were carried out in the Region of the Americas in the period of 1996-2001. METHODS: External quality control proficiency tests of dengue serological diagnosis were carried out in 1996-1997, 1998-1999, 1999-2000, and 2000-2001. Panels made up of 20 serum samples (12 of them positive for dengue IgM antibodies) were sent to participating laboratories in the Region. The sera were negative for HIV antibodies, hepatitis C virus antibodies, and hepatitis B surface antigen. The sera were stored at -20 degrees C until they were sent in refrigerated shipments to the participating laboratories. The presence of IgM antibodies was determined through IgM-capture enzyme-linked immunosorbent assay (ELISA), while the IgG antibody titer was determined by hemagglutination inhibition or by IgG ELISA. The results of the IgM antibody testing that differed from those of the reference center were considered discordant. The IgG antibody titer was considered discordant when the results differed by two dilutions or more with respect to the reference center's results. RESULTS: A total of 27 laboratories received a total of 59 serum panels over the 1996-2001 period, and the results from testing 54 of those panels (91.5%) were sent back in. Of the total of 1 080 sera samples from those 54 panels, the results from 95.6% of the IgM antibody tests were concordant with the results from the reference center. With 47 of the 54 panels (87.0%) the participating laboratories' agreement with the reference center's results for the IgM antibody testing was 90.0% or higher. The laboratories sent back results from a total of 27 IgG antibody titer tests, and 22 of them (81.5%) coincided with those from the reference center. Considering the IgM antibody testing results from the four periods, the findings from 22 of the participating laboratories coincided with those from the reference center for at least 90% of the samples, and 13 of the laboratories were in complete concordance with the reference center. CONCLUSIONS: The majority of the participating laboratories showed an excellent level of performance in detecting dengue IgG and IgM antibodies. However, the deficiencies found in some instances confirm the need for continuing to improve laboratory diagnosis of dengue in the Region of the Americas.