Serodiagnosis of Lyme borreliosis using detection of different immunoglobulin (sub)classes by enzyme-linked immunosorbent assay and Western blotting

To improve the performance of enzyme-linked immunosorbent assays for the serodiagnosis of Lyme borreliosis, the prevalence of several immunoglobulin classes and subclasses against various antigens of Borrelia burgdorferi was investigated by Western blotting. The sera of 40 early Lyme borreliosis patients (ELB), 27 late Lyme borreliosis patients (LLB), 62 healthy controls and 140 non-Lyme borreliosis patients were used. Detection of IgG1 versus total IgG was found to be more sensitive in detecting Borrelia burgdorferi antigens, especially flagellin (41 kD) protein, but did not improve the performance of Western blotting. The use of IgG1 detection showed an increase in sensitivity and specificity for the early Lyme borreliosis patient group compared to the standard IgG and IgM detection method by enzyme immunoassays using purified Borrelia burgdorferi flagellum. However, in an enzyme immunoassay using a total sonicate, sensitivity in detecting early Lyme borreliosis and late Lyme borreliosis with IgG1 remained lower compared to the detection of early Lyme borreliosis by IgM antibodies and late Lyme borreliosis by total IgG antibodies.     

Development and laboratory evaluation of a new recombinant ELISA for the serodiagnosis of Lyme disease

OBJECTIVE: The use of recombinant proteins for serologic testing represents a modern approach for the improved laboratory diagnosis of Lyme disease (LD). The aim of the present study was to develop and evaluate a new recombinant ELISA (RE) for the detection of specific IgG and IgM antibodies against Borrelia burgdorferi. MATERIALS AND METHODS: The RE (Biotest AG, Dreieich, Germany) uses mixtures of recombinant p100, OspC, p18 of Borrelia afzelii and a fusion protein of recombinant internal fragments of the flagellum protein (p41) of Borrelia garinii strain PBi and Borrelia afzelii strain PKo. Serologic testing was performed on a commercially available ELISA processor without pre-absorption of sera. The sensitivity of the RE was determined by testing 226 sera obtained from patients suffering from Lyme disease (stage I: n = 148, stage II: n = 35, stage III: n = 43). Specificity of the RE was evaluated in 1107 sera from healthy blood donors and 275 sera from patients with other infectious diseases or autoimmune illnesses (leptospirosis: n = 53, syphilis: n = 70, toxoplasmosis: n = 60, herpes simplex virus: n = 30, HIV: n = 30; rheumatoid-factor positive: n = 32). In addition, 394 routine samples were prospectively tested in comparison with a well established whole-cell lysate extract ELISA (ENZYGNOST Borreliosis, DadeBehring, Germany) for relative sensitivity and specificity. RESULTS: Overall specificity, determined in 1107 healthy blood donors and 275 sera from patients with other diseases, was 94% for IgG and 91% for IgM. The overall sensitivities in 226 sera obtained from patients suffering from different stages of LD were 67-95%. Moreover, as revealed by prospective testing of 394 routine samples, the relative sensitivity of the RE in comparison with an established whole-cell lysate extract ELISA in the detection of seropositive samples was 81.1% for IgG and 86.5% for IgM with a relative specificity of 98.5% and 93% respectively. The ELISAs showed an overall agreement of 97% for IgG and 92.4% for IgM test results. CONCLUSION: The RE proved to be a reliable and specific screening test in the routine serodiagnosis of LD. In addition, the RE is easy to perform and requires no pre-absorption.     

Simultaneous expression of Borrelia OspA and OspC and IgM response in cerebrospinal fluid in early neurologic Lyme disease.

Lyme disease is the major tick-borne disease, caused by Borrelia burgdorferi (Bb). Neurological involvement is common in all stages. In vivo expression of Bb antigens (Ags) and the immune response to them has not been well investigated in the cerebrospinal fluid (CSF). Upregulation of outer surface protein (Osp) C and concomitant downregulation of OspA before tick inoculation of the spirochete has been reported in skin and blood in animals. CSF OspA Ag in early disease suggests otherwise in CSF. Early Ag expression and IgM response in human CSF was investigated here. Paired CSF and serum was collected from 16 early, predominantly erythema migrans Lyme disease patients with neurologic problems, 13 late Lyme disease patients, and 19 other neurologic disease (OND) controls. Samples were examined for IgM reactivity to recombinant Bb-specific Osps using ELISA and immunoblot. Of 12 early Lyme disease patients with neurologic involvement with both CSF and serum IgM against OspC, 7 (58%) had IgM to OspA (n = 5) or OspB (n = 2) that was restricted to the CSF, not serum. Overall, 12 of 16 (75%) of these early Lyme disease patients with neurologic involvement had CSF and serum IgM against OspC. Only 3 of 13 (23%) late Lyme disease patients and none of 19 OND controls had CSF IgM directed against OspC. In conclusion, in CSF, OspC and OspA can be coexpressed, and IgM response to them occurs in early Lyme disease patients with neurologic involvement. This biologic finding may also provide a discriminating marker for CNS infection in Lyme disease.     

用基因工程抗原建立ELISA检测莱病特异IgM抗体

目的 利用伯氏疏螺旋体基因工程抗原外膜蛋白C（OspC)建立间接ELISA，检测莱姆病特异性抗体IgM。方法 基因工程抗原OspC的包被浓度和酶标抗μ链单抗所用浓度及血清稀释倍数，均由方阵滴定法确定，并进行精密度、特异性试验、阻断试验和干扰试验。结果 OspC最佳浓度为150μg/L，批内平均变异系数4．6％，批间平均变异系数14．2％，用ELISA测定临床已确诊莱姆病33例，57例正常体检者，同时与进口ELISA试剂盒比较，两方法符合率97．8％。结论 该方法特异性强、敏感性高、实验结果可靠,是莱姆病早期诊断的好方法。     

Evaluation of in vivo expressed Borrelia burgdorferi antigens for improved IgM serodiagnosis of early Lyme disease

Improved serologic tests are needed for accurate diagnosis and proper treatment of early stage Lyme disease. We evaluated the 3 antigens currently used for 2-tiered IgM immunoblot testing (FlaB, OspC, and BmpA) in combination with 3 additional antigens (BBA65, BBA70, and BBA73) and measured the sensitivity and specificity against a serum repository of positive and negative controls. Using 3 statistical methods for positivity cutoff determinations and scoring criteria, we found increased sensitivities for early Lyme disease when 2 of 6 antigens were positive as compared with the 2 of 3 antigen IgM criteria currently used for second-tier immunoblot scoring. Specificities for negative controls were comparable or superior to using 2 of 3 antigens. These results indicate that IgM sensitivity and specificity of serological testing for Lyme disease in the early stages of illness can be improved by employing antigens that target the initial host antibody responses.     

Detection of anti-Borrelia antibodies by immunoblotting in Lyme borreliosis

IgM and IgG were detected in the sera from 25 Russian patients with Lyme disease by immunoblotting test with Immunetics kit (USA). Early stage of the disease was diagnosed in 12 patients and late stage in 13. Specific protein lines were detected in virtually all patients but their number and combination in the sera were different. Eleven (43%) sera were regarded as positive according to the American criteria of seropositive test, 3 of them by IgM and 10 by IgG. In patients with short disease serum reaction was either negative or confined to 1-2 lines per strip. Patients with late stage showed a more manifest extensive reaction, which was the most pronounced in patients with a long lasting disease and articular involvement; the reaction was similar to that characteristic of chronic Lyme arthritis. Parallel testing of IgG antibodies in 25 sera from American patients with Lyme disease (confirmed by direct isolation of the agent) showed notable similarity of reactions of both American and Russian sera. More essential differences were observed only for low molecular weight proteins (p28, p23, p21).     

Evaluation of four commercially available ELISA assays for the serologic diagnosis of Lyme disease

We evaluated four commercially available ELISAs for detection of antibody to Borrelia burgdorferi with 21 sera from patients with clinically diagnosed Lyme disease and 89 patient control sera. Patient control sera included 28 sera from patients with rheumatoid arthritis (RA), 17 sera from patients with systemic lupus erythematosus (SLE), and 44 sera containing antibodies reported to cross-react in some Lyme disease tests. The ELISAs tested (Cambridge Bioscience, Diamedix, 3M, and Zeus) detect antibodies (IgM and/or IgG) that bind Borrelia burgdorferi antigen attached to microtiter wells. Antibody reactivity in the sera from patients with clinically diagnosed Lyme disease was characterized by using Zeus immunoglobulin class-specific assays (IgM and IgG). Sensitivities in early and late Lyme disease were as follows: Cambridge and Diamedix, 57% and 100%; 3M, 57% and 93%; and Zeus, 71% and 86%. Reactivities within a patient control population were: Cambridge and Diamedix, 3%; 3M, 7%; and Zeus, 10%.     

Evaluation of immunofluorescence test (IFT) and immuno (western) blot (WB) test in patients with erythema migrans

The diagnosis of Lyme borreliosis is based on the recognition of typical clinical signs and is assisted by laboratory confirmation of borrelial infection. The aim of the present study was to assess the value of an immunofluorescence test (IFT) and an immuno (western) blot (WB) test for the detection of Borrelia burgdorferi sensu lato antibodies in patients with erythema migrans residing in Slovenia. We determined specific IgM and IgG antibodies in 117 patients with erythema migrans and 96 healthy persons using an IFT (in-house test) and a commercial WB test. Skin biopsies of erythema migrans lesions were cultured, and isolated strains were identified with PFGE. There were 66/117 (56.4%) culture-positive and 51/117 (43.6%) culture-negative patients. B. afzelii was found in 52/62 (84%) and B. garinii in 10/62 (16%) biopsies. IFT-IgM antibodies were established in 2/117 (1.7%) erythema migrans patients and in none of the control group, while WB-IgM antibodies were present in 56/117 (48%) patients with erythema migrans and 21/96 (22%) members of the control group (p = 0.002). IFT-IgG antibodies were demonstrated in 3/117 (2.2%) erythema migrans patients and 2/96 (4%) persons of the control group, while corresponding values for WB-IgG were 36/117 (31%) and 26/96 (27%), respectively (non-significant differences). IgM antibodies directed against p41 and OspC, and IgG antibodies directed against p41, p18 and OspC were frequently found in both erythema migrans patients and the control group. The only significant difference between erythema migrans patients and the control group in the WB test was in the reaction of IgM antibodies with OspC antigen, which was found in 54/117 (46%) erythema migrans patients and 18/96 (18.8%) healthy persons (p < 0.0001). The immune response in patients with erythema migrans was very similar to that of the control group determined with either the IFT or WB test.     

Epidemiology and diagnosis of Lyme borreliosis

The multisystem disease Lyme borreliosis is the most frequent tick-transmitted disease in the northern hemisphere. In Europe Lyme borreliosis is most frequent in Central Europe and Scandinavia (up to 155 cases per 100,000 individuals) and is caused by the species, B. burgdorferi sensu stricto, B. afzelii and B. garinii. The recently detected genospecies A14S may also play a role in skin manifestations. Microbiological diagnosis in European patients must consider the heterogeneity of borreliae for development of diagnostic tools. According to guidelines of the USA and Germany, serological diagnosis should follow the principle of a two-step procedure (enzyme-linked immunosorbent assay (ELISA) as first step, if reactive; followed by immunoblot). The sensitivity and standardization of immunoblots has been considerably enhanced by use of recombinant antigens (p100, p58, p41i, VlsE, OspC, DbpA) including those expressed primarily in vivo (VlsE and DbpA) instead of whole cell lysates. VlsE is the most sensitive antigen for IgG antibody detection, OspC for IgM antibody detection. At present, detection rates for serum antibodies are 20%-50% in stage I, 70%-90% in stage II, and nearly 100% in stage III Lyme disease. Detection of the etiological agent by culture or polymerase chain reaction (PCR) should be confined to specific indications and specialized laboratories. Recommended specimens are skin biopsy specimens, cerebrospinal fluid (CSF) and synovial fluid. The best results are obtained from skin biopsies with culture or PCR (50%-70%) and synovial tissue or fluid (50%-70% with PCR). CSF yields positive results in only 10%-30% of patients except when the duration of symptoms is shorter than 2 weeks (50% sensitivity). Methods which are not recommended or adequately documented for diagnosis are antigen tests on body fluids, PCR of urine, and lymphocyte transformation tests.     

Comparison of immunofluorescence assay (IFA) and LIAISON® in patients with different clinical manifestations of Lyme borreliosis

Serological tests for detection of borrelial antibodies are frequently used in laboratory diagnostics of Lyme borreliosis. Unfortunately these tests are not standardized and the results obtained with different assays may not be concordant. The aim of the present study was to compare two different serological tests, IFA and LIAISON, for detection of Borrelia burgdorferi sensu lato IgM and IgG antibody. We analyzed the serological immune response in 383 patients with different clinical manifestations of Lyme borreliosis and in 49 healthy blood donors. LIAISON detected IgM and IgG antibodies more often than IFA in all groups of patients except those with chronic Lyme borreliosis. The differences were significant for IgM and IgG antibodies in patients with solitary erythema migrans and in those with early disseminated Lyme borreliosis. There was no significant difference in the specificity of the two tests.     

Antigens of Borrelia burgdorferi recognized during Lyme disease. Appearance of a new immunoglobulin M response and expansion of the immunoglobulin G response late in the illness.

Using immunoblots, we identified proteins of Borrelia burgdorferi bound by IgM and IgG antibodies during Lyme disease. In 12 patients with early disease alone, both the IgM and IgG responses were restricted primarily to a 41-kD antigen. This limited response disappeared within several months. In contrast, among six patients with prolonged illness, the IgM response to the 41-kD protein sometimes persisted for months to years, and late in the illness during arthritis, a new IgM response sometimes developed to a 34-kD component of the organism. The IgG response in these patients appeared in a characteristic sequential pattern over months to years to as many as 11 spirochetal antigens. The appearance of a new IgM response and the expansion of the IgG response late in the illness, and the lack of such responses in patients with early disease alone, suggest that B. burgdorferi remains alive throughout the illness.     

Antigen biochips verify and extend the scope of antibody detection in Lyme borreliosis

The antibody response of serum IgM and IgG of patients with neuroborreliosis and erythema migrans of Lyme borreliosis (LB) was examined against a 41-kDa flagellar antigen and an 8-mer synthetic OspC8 peptide (VAESPKKP) derived from the C-terminus of outer surface protein C (OspC) from Borrelia garinii. We developed a streptavidin-modified biochip-based immunodiagnosis and compared it with conventional methods such as enzyme-linked immunosorbent assay (ELISA) and Western blot (WB). The diagnostic sensitivity of the coated biochips was demonstrated to be identical, and the results of conventional assays such as ELISA and WB were confirmed. Flagellar antigens lead to better diagnosis because of a higher discriminative value. By contrast, OspC8, a peptide derived from the outer surface antigen, is less sensitive to identify immunity in LB. The inferior antigenicity of OspC8 may be due to epitope masking. Overall, this system is open to simultaneously analyze a larger family of peptides differing in length. Thus, an array approach is generally more advantageous to extend the pattern of antigens to be tested for antigenicity in LB. Serial analysis during ongoing disease may be valuable to learn more about the course of the disease and intermittent reactivation of infection. Protein biochip as a potential substitution of ELISA and WB method offers the opportunity to study serum immunity in a multiplicity of patients simultaneously.     

IgG heavy-chain subclass typing of myeloma paraproteins by isoelectric focusing immunoblot analysis

The objective of this study was to develop a clinical laboratory method for subclass typing of human immunoglobulin G (IgG) paraproteins. Serum proteins were isoelectrically focused (IEF) in a mini-gel and passively blotted by capillary diffusion onto untreated nitrocellulose. Unreacted sites on the nitrocellulose were blocked with bovine serum albumin and the bound IgG was detected with peroxidase-conjugated anti-human IgG1-4 monoclonal antibodies from WHO/IUIS clones. The IEF immunoblot specificity was demonstrated by analysis of documented IgG, IgA, and IgM myeloma proteins of known subclass and light-chain composition. IEF immunoblots of sera from 18 myeloma patients who had an above-normal total IgG concentration produced IEF immunoblot patterns composed of five to 10 discrete bands (pI range 6.0 to 8.4). In contrast, no detectable IgG bands were observed with sera containing IgA and IgM paraproteins. The observed subclass frequencies of IgG paraproteins were 56% IgG1 (10/18), 28% IgG2 (5/18), 11% IgG3 (2/18), and 5% IgG4 (1/18). IEF immunoblot analysis permits the monitoring of changes in the pI and subclass of an IgG paraprotein over the course of a myeloma patient's therapy program.     

Evaluation of commercial screening tests and blot assays for the diagnosis of Lyme borreliosis

The performance of 4 screening tests and 10 blot assays for the serologic diagnosis of Lyme borreliosis in a Belgian population was evaluated. A total of 196 sera were tested: 36 Lyme borreliosis at different stages of the disease, 50 healthy blood donors, and 110 representing various clinical circumstances. The DiaSorin Liaison and Euroimmun Anti-Borrelia screening tests were evaluated. The tested blot assays were Virotech Borrelia LINE tests WE222, WE225, and WE224, as well as Mikrogen recomLine Borrelia and Viramed ViraStripe. The specificity of IgG was acceptable for the different assays. For IgM, DiaSorin Liaison Borrelia IgM Quant, Mikrogen recomLine, and Viramed ViraStripe lacked specificity. Interestingly, a higher rate of falsely reactive samples was observed in the group of patients suffering from malaria. Serological diagnosis of Lyme borreliosis remains challenging; assays should be evaluated in the population where they are intended to be used.     

Epidemiology and diagnosis of Lyme borreliosis

The multisystem disease Lyme borreliosis is the most frequent tick‐transmitted disease in the northern hemisphere. In Europe Lyme borreliosis is most frequent in Central Europe and Scandinavia (up to 155 cases per 100,000 individuals) and is caused by the species, B. burgdorferi sensu stricto, B. afzelii and B. garinii. The recently detected genospecies A14S may also play a role in skin manifestations. Microbiological diagnosis in European patients must consider the heterogeneity of borreliae for development of diagnostic tools. According to guidelines of the USA and Germany, serological diagnosis should follow the principle of a two‐step procedure (enzyme‐linked immunosorbent assay (ELISA) as first step, if reactive; followed by immunoblot). The sensitivity and standardization of immunoblots has been considerably enhanced by use of recombinant antigens (p100, p58, p41i, VlsE, OspC, DbpA) including those expressed primarily in vivo (VlsE and DbpA) instead of whole cell lysates. VlsE is the most sensitive antigen for IgG antibody detection, OspC for IgM antibody detection. At present, detection rates for serum antibodies are 20%–50% in stage I, 70%–90% in stage II, and nearly 100% in stage III Lyme disease. Detection of the etiological agent by culture or polymerase chain reaction (PCR) should be confined to specific indications and specialized laboratories. Recommended specimens are skin biopsy specimens, cerebrospinal fluid (CSF) and synovial fluid. The best results are obtained from skin biopsies with culture or PCR (50%–70%) and synovial tissue or fluid (50%–70% with PCR). CSF yields positive results in only 10%–30% of patients except when the duration of symptoms is shorter than 2 weeks (50% sensitivity). Methods which are not recommended or adequately documented for diagnosis are antigen tests on body fluids, PCR of urine, and lymphocyte transformation tests.     

Serologic evidence for tick-borne pathogens other than Borrelia burgdorferi (TOBB) in Lyme borreliosis patients from midwestern Germany

The seroprevalence of antibodies against the human granulocytic ehrlichiosis agent (HGE) and Babesia microti was retrospectively determined in 76 Lyme borreliosis patients and in 44 asymptomatic individuals with a positive borreliosis serology, in comparison to 100 healthy blood donors from the Rhein-Main area. Additionally, seroreactivity for tick-borne encephalitis virus (TBEV) was investigated. For antibody detection, commercially available immunofluorescence assays (MRL Diagnostics, USA) and a TBEV-ELISA (Immuno, Germany) were used. In the control group, the positivity rate for anti-Borrelia burgdorferi (IgG/IgM) and anti-Babesia microti-antibodies in the population of the Rhein-Main area (Midwestern Germany) may be estimated at 15% and 8%, respectively. Examination for both HGE and TBEV demonstrated seroreactivity (IgG) in 1% of tested individuals. Specific anti-HGE IgG and/or IgM antibodies were more often discovered in cases of early Borrelia infection (stage I: 13.6%, stage II: 18.4%) than in patients with stage III disease (0%) or in seropositive but asymptomatic patients (6.8%). Investigation for TBEV revealed seroreactivity for IgG in 13% of these cases. No TBEV-IgM was found. Interestingly, the prevalence of anti-HGE and anti-TBEV antibodies among Lyme borreliosis patients and seropositive patients without active Lyme disease symptoms was significantly higher than that in the control group of healthy blood donors (p < 0.05). Likewise, antibody titers reflecting a recent infection with Babesia microti could be demonstrated more often in patients with Lyme borreliosis stage I or II (p < 0.05). Analysis of 50 samples from patients with florid or recent syphilis infection revealed no crossreactivity between Babesia microti, HGE and Treponema pallidum. Our findings suggest that concomitant or serial infection due to TOBB may be common in tick exposed patients from the Rhein-Main area and in European countries in general. Hence, in addition to TBEV, human babesiosis and HGE should always be considered by European physicians in the differential diagnosis of acute febrile illness following a tick bite.     

Performance characteristics of the Euroimmun enzyme-linked immunosorbent assay kits for Brucella IgG and IgM

Brucella IgG and IgM ELISA kits manufactured by Euroimmun (Lubeck, Germany) were evaluated in a reference laboratory setting. Intraassay coefficient of variation (CV) values were ≤10% for positive sera and ≤12% for negative sera; interassay CVs were ≤12% for positive sera and ≤20% for negative sera. The tube agglutination test (TAT) was performed on 51 sera exhibiting various ELISA reactivity profiles. All 18 sera negative for both IgG and IgM by ELISA were TAT negative (titer <1:80), whereas 31 (94%) of 33 sera positive for IgG and/or IgM were TAT positive; the 2 discordant sera were IgG positive IgM negative by ELISA. None of 41 sera from healthy laboratory employees were ELISA IgG positive, whereas 1 (2%) of 41 was ELISA IgM positive. Similarly, 0 of 149 potentially cross-reactive sera (containing rheumatoid factor or antibodies to selected Gram-negative bacteria) was ELISA IgG positive, whereas 4 (3%) of 149 were ELISA IgM positive. These findings demonstrate the acceptable performance of the Euroimmun ELISAs for Brucella antibodies.     

Erythema migrans and serodiagnosis by enzyme immunoassay and immunoblot with three borrelia species

There is wide divergence of opinion between physicians regarding the use of serological measures for the diagnosis and treatment of erythema migrans, the hallmark of Lyme borreliosis. We studied the outcome of an enzyme immunoassay and immunoblot (Western blot) used on the sera of patients who had suffered tick bite and erythema migrans, and had been subsequently treated with various antibiotics. Ninety-nine consecutive patients presenting with erythema migrans after tick bite were prospectively recruited at the outpatient department of two Vienna City hospitals and at the consultation office for Lyme borreliosis of the Institute of Hygiene. University Vienna. Blood samples were taken before antibiotic treatment and 3 and 6 months thereafter. Blood samples from 100 blood donors served as controls. Antibodies against Borrelia burgdorferi sensu lato were determined by enzyme immunoassay (IgG and IgM EIA) and by IgG immunoblot. The latter was performed with isolates of B. alzelii (H2) B. burgdorferi sensu stricto (Le) and B. garinii (W) from Austrian patients. The 4 interpretation criteria for immunoblot results were: A (3 bands out of 8), B (2 bands out of 9), C and D (1 band out of 6). In all patients, the erythema resolved within the treatment period. No complications secondary to the borrelia infection were registered. After treatment there was no significant change in titre, nor was there a difference in the immunoblot pattern between the first, second and third serum samples. Serum antibodies to B. burgdorferi were positive by EIA in 22.9% (IgG) and 2.5% (IgM). Immunoblot results offered by borrelia species and by the interpretation criteria, ranging between 8.3% (criterion A, strain Le) and 44.2% (criterion D, strain H2). By EIA, control samples were IgG and IgM positive in 5% and 1%, respectively. Positive immunoblot results with strain H2 were found in 9%, 13%, 18%, and 20% by the criteria A through D respectively. After antibiotic treatment of erythema migrans the immunological response appears to be abrogated. Thus, serological results are not supportive for the diagnosis of erythema migrans, not will they retrospectively prove successful antibiotic treatment of borrelia infection.     

Comparison of the Brucella Standard Agglutination Test with the ELISA IgG and IgM in patients with Brucella bacteremia

The presumptive diagnosis of Brucellosis is based on a high or rising antibody titer measured by the Brucella Standard Agglutination Test (SAT). This tests does not discriminate between the immunoglobulin classes (IgG and IgM). The purpose of this study was to compare the diagnostic value of SAT with Brucella Enzyme Linked Immunosorbent Assay (ELISA) IgG and IgM tests in patients with Brucella bacteremia. Over a one-year period, we had 68 patients with clinical features suggestive of Brucellosis who had positive blood cultures for Brucella species. Sera were obtained from all of the patients as well as a control group of 70 healthy military personnel who were blood donors and had no symptoms of Brucellosis. Patients and blood donors originated from the same referral population. All the sera were tested by SAT and ELISA. All the 70 controls had a negative SAT. The sensitivity and specificity of the SAT test for the bacteremic patients were 95.6% and 100.0% respectively, while that of the ELISA IgG were 45.6% and 97.1%, and that of the ELISA IgM were 79.1% and 100.0% respectively. The sensitivity and specificity of either IgG or IgM positivity were 94.1% and 97.1% respectively. Assuming that the population prevalence of active Brucellosis in Saudi Arabia (SAT >or=1:320) is 5%, the positive and negative predictive values of SAT were 100% and 99.7% respectively; of ELISA IgG they were 45.2% and 97.1%; and of ELISA IgM they were 100% and 98.9%. When both the ELISA IgG and IgM were combined, the positive and negative predictive values were 63% and 99.6% respectively. In patients with Brucella bactremia, the sensitivity of either ELISA IgM or IgG were lower than SAT, however, combining IgM and IgG had similar sensitivity and specificity to SAT. The positive predictive value of SAT and IgM is satisfactory.     

IFA和ELISA在肿瘤患者血清SARS-CoV抗体测定中的对比分析

目的探讨酶联免疫吸附试验(ELISA)和间接免疫荧光法(IFA)检测严重急性呼吸综合征(SARS)冠状病毒(SARS-CoY)&体在SARS病原中诊断中的特异性及其在肿瘤患者血清中的假阳性问题。方法 应用ELISA和IFA检测了111例正常对照和40例肿瘤患者血清中SARS-CoV抗体的阳性率。结果在111例正常对照和40例肿瘤患者中,IgM抗体均阴性,IgG抗体在正常对照中的阳性率为3.6%(4/111),在肿瘤患者中的阳性率17.5％(7/40),IgC抗体诊断SARS的特异性为96.4％,两种抗体同时阳性诊断SARS的特异性为100％。经IFA检测,上述SARS-CoV抗体阳性者均为阴性。结论 IFA诊断SARS的特异性为100％,ELISA诊断SARS存在一定的假阳性。应用ELISA测定SARS-CoV抗体时,应同时测定两种抗体以降低诊断的假阳性率,提高诊断的特异性。