Comparison of commercial kits for the detection of anti-nDNA antibodies using Crithidia luciliae

The reactions of sera from 15 selected patients with connective tissue diseases and 4 selected control people were compared with the use of five commercial kits detecting anti-nDNA antibodies by indirect immunofluorescence on Crithidia luciliae. The cases with systemic lupus erythematosus (SLE) and a related condition reacted with the kinetoplasts of the C. luciliae in each kit tested with one exception, notably a case of drug-induced LE. The four control cases selected for a trace of staining of the nuclei of C. luciliae gave negative reactions with the kinetoplasts. The titer for each individual positive serum varied from 1.36 to 2.67 (mean SG 2.04) geometric standard deviation units. The staining pattern of sera positive for anti-nDNA antibodies on C. luciliae included reactivity of the kinetoplast with or without nuclear staining. The drug-induced LE serum produced only nuclear staining with no significant kinetoplast staining, i.e., a negative test for anti-nDNA antibodies. Patient control sera stained only the nucleus when any reactivity on C. luciliae was present. Generally, there were no major differences in titers and patterns of sera when comparisons were made between manufacturers. The sera were also tested by the Farr radioimmunoassay and the latex nucleoprotein test. The results of both of these assays correlated in most cases with the C. luciliae reactions.     

Comparison of three commercial ELISA kits for the detection of turkey rhinotracheitis virus antibodies.

Three commercial ELISAs (Pathasure, Svanovir and Flockscreen) were compared in their ability to detect turkey rhinotracheitis virus (TRTV) vaccine-induced antibodies. Sequential sera taken from specified pathogen-free chickens, vaccinated with two combinations of live and inactivated TRTV vaccines were used. The vaccines were based on TRTV strains from the United Kingdom (Intervet) and from France (Rhone Merieux). One ELISA failed to detect antibodies after live vaccination with both French and UK vaccines, but detected antibodies induced by both inactivated vaccines by 8 days after vaccination. The two other ELISAs responded to both live vaccinations equally well and both detected a rise in antibody level 8 days after the inactivated vaccination. The specificity of the three ELISAs was 100%. When tested on field samples, all three ELISAs indicated a high prevalence of TRTV antibodies in turkey flocks in the Netherlands.     

Comparison of seven commercial enzyme-linked immunosorbent assays for the detection of anti-diphtheria toxin antibodies

Determination of immune status of patients to diphtheria toxin is based mainly on the results of commercially available ELISA kits. The aim of the present study was to compare the results obtained by ELISAs from seven different manufacturers: Mikrogen, Immunolab, Sekisui Virotech, NovaTec, VirionSerion, IBL International and Euroimmun. All assays were performed according to the manufacturers’ instructions. The concentrations of the anti-diphtheria toxin antibodies in 72 serum samples were calculated on the basis of curves constructed from standards supplied by manufacturers and the new reference material—International Standard for Diphtheria Antitoxin (10/262). The repeatability and reproducibility of all the ELISA kits tested were good. Number of sera with concentrations of the anti-diphtheria toxin antibodies below the WHO-recommended level of protection (0.1 IU/ml) were dependent on the ELISA used: Mikrogen, 20/72 samples (27.7 %); Immunolab, 11/72 samples (15.3 %); Sekisui Virotech, 0/72 samples (0 %); NovaTec 18/72 samples (25.0 %); Serion 12/72 samples (16.7 %); IBL International, 7/72 samples (9.7 %); and Euroimmun, 17/72 samples (23.6 %). However, the results obtained in particular ELISAs, with the exception of Sekisui Virotech, were much more consistent when the concentrations of the anti-diphtheria toxin antibodies in 72 sera measured by using curves constructed from the International Standard 10/262. The data obtained clearly demonstrated that manufacturer-dependent differences between anti-diphtheria IgG ELISA kits exist. The differences in recommendations accepted by the individual manufacturers together with differences shown in our studies in sensitivity greatly affect the clinical interpretation of results.     

Comparison of commercial kits for detection of cryptococcal antigen.

Although kits to detect cryptococcal antigen are used widely to diagnose cryptococcal infection, the comparative performance of commercially available assays has not been evaluated in the past decade. Therefore, we compared the sensitives and specificities of five commercially available kits for detecting cryptococcal antigen (four latex agglutination test kits--Calas [Meridian Diagnostics])--Crypto-LA [International Biological Labs], Myco-Immune [MicroScan], and Immy [Immunomycologics]--and an enzyme immunoassay kit, Premier [Meridian Diagnostics]) with culture for the diagnosis of cryptococcal meningitis and fungemia. Of 182 cerebrospinal fluid (CSF) and 90 serum samples submitted for cryptococcal antigen and fungal culture, 49 (19 and 30 samples, respectively) from 20 patients had a culture positive for Cryptococcus neoformans. For CSF specimens, the sensitivities and specificities of all kits were comparable (sensitivity, 93 to 100%; specificity, 93 to 98%). There was a significant difference in sensitivities of the kits when serum samples were tested with the International Biological Labs and MicroScan kits, which do not pretreat serum with pronase. These kits were less sensitive (sensitivity, 83%) than the Immy and Meridian latex kits (sensitivity, 97%), which do pretreat with pronase. The sensitivity of the Meridian enzyme immunoassay kit was comparable to that of the pronase-containing latex kits. These kits were of equivalent specificities (93 to 100%) when testing serum. Some of the currently available kits have limitations that need to be recognized for proper interpretation of results. Specifically, the use of pronase on serum samples reduces the number of false-positive results, and a titer of < or = 1:4 can be a false-positive result when CSF samples are being tested.     

Monoclonal antibodies for detection of lymphocyte markers: comparison of three commercial kits

Three commercial monoclonal antibody kits (Histoset, OrthoDiagnostics, Raritan, NJ; T Cell Panel, Becton Dickinson, Mountain View, CA; Histotag Lymphoma Set, Hybritech Inc., San Diego, CA) were compared, using touch preparations, frozen sections, and formalin-fixed paraffin-embedded sections of 14 tonsils. With the first two kits, sensitive results were obtained in touch preparations and frozen sections with strong, crisp, reproducible immunostain. Results were accurate and easily interpreted despite moderate background staining. Distribution and numbers of lymphocytes and subsets were appropriate. The Histotag Lymphoma Set was sensitive for detection of T-cells in touch preparations and frozen sections. Hazy, moderate immunostain was obtained with B-cell and common leukocyte antibodies. Accuracy was questioned because of variable and false-negative results (75% in touch preparations) with all anti-sera, and interfollicular staining for B-lymphocytes. In formalin-fixed sections, positive results of low sensitivity were obtained only with the T Cell Panel. The Histoset and T Cell Panel are recommended, particularly for use with frozen sections.     

Comparison of six different commercial IgG-ELISA kits for the detection of TBEV-antibodies

BACKGROUND: Tick-borne encephalitis virus (TBEV) is a pathogenic human flavivirus endemic in some parts of Europe and Asia. Commercial enzyme immunoassays (EIA) for the detection of IgG antibodies are often used in TBEV-seroprevalence studies, as well as for the confirmation of a successful vaccination against TBEV. However, the detection of TBEV-specific antibodies can be biased by the cross-reactivity between different flavivirus genera. OBJECTIVES: To compare different EIA test systems for the detection of TBEV-IgG antibodies. STUDY DESIGN: Six commercial EIA kits for the detection of TBEV-specific antibodies are compared, using serum panels (n=139) of subjects with a documented clinical history (109 sera from TBEV infected patients, 30 sera from people vaccinated against TBEV). For the analysis of possible cross-reactivities, 24 sera from yellow fever vaccinated people and 13 sera positive for Dengue virus-specific antibodies were also included. RESULTS: The sensitivity of the different TBEV test systems ranges from 73 to 99%. However, when testing the yellow fever and Dengue virus positive specimens, problems with the flavivirus cross- reactivity become obvious, resulting in specificities between 14 and 81%. CONCLUSIONS: This study shows the necessity of further improvement of the existing TBEV test systems regarding both sensitivity and specificity.     

Comparison of three commercial cryptococcal latex kits for detection of cryptococcal antigen

Three commercial latex kits, IBL, MYCO-Immune, and IMMY, for the detection of cryptococcal antigen were compared in regard to sensitivity, specificity, and height of antigen titers. A total of 218 cerebrospinal fluid and 79 serum specimens from 239 patients were included. Twenty-two patients had culture-proven disseminated cryptococcosis. Both the IBL and MYCO-Immune kits had sensitivities of 100%, and the IMMY kit had sensitivities of 82.6 and 45.4% in CSF and serum specimens, respectively. There was one false-positive reaction in serum with the MYCO-Immune kit and one false-negative reaction on screen only with all three kits. Rheumatoid factor-containing sera were used to check the agglutination titers between matching anti-cryptococcal globulin reagents and normal globulin reagents. The finding that agglutination titer with anti-cryptococcal globulin reagents was fourfold higher than with normal globulin reagents in the MYCO-Immune kit is considered to be a cause for a false-positive reaction in serum.     

Evaluation of two commercial enzyme-linked immunosorbent assay kits for the detection of Mycoplasma gallisepticum antibodies

Sensitivity and specificity of two commercial Mycoplasma gallisepticum (MG) enzyme-linked immunosorbent assay (ELISA) kits, rapid slide agglutination (SA) and haemagglutination inhibition (HI) tests were compared using sera from specific pathogen free chickens, turkeys or ducks which had been inoculated with various avian mycoplasmas, bacteria or with a reovirus. Results show that sensitivity of SA was superior to ELISA and HI tests in the ability to detect antibodies formed in early response to MG infection. However, both ELISA kits and HI tests had a higher degree of specificity.     

Comparison of five commercial western blot kits for detection of human immunodeficiency virus 1

Twenty-two human immunodeficiency virus 1 (HIV-1) enzyme immunoassay (EIA) reactive and two non-reactive patient specimens were analyzed using five commercially available HIV-1 Western blot kits. The percentage of HIV-1 bands detected by each kit was recorded. The differences between pairs of kits were not found to be statistically significant at the 0.05 level. All EIA reactive specimens were reconfirmed as reactive by each Western blot kit tested.     

Comparison of two commercial microimmunofluorescence kits and an enzyme immunoassay kit for detection of serum immunoglobulin G antibodies to Chlamydia pneumoniae

We compared the MRL and the Labsystems Chlamydia pneumoniae microimmunofluorescence (MIF) immunoglobulin G (IgG) kits and the Labsystems enzyme immunoassay (EIA) kit in a blinded study of 83 serum samples in which we evaluated titers, cross-reactivity to other species, and reproducibility. There was no statistically significant difference between the MRL and the Labsystems MIF kits in the endpoint titers of IgG antibody to C. pneumoniae. The correlation between the results obtained with these two MIF kits was excellent (r = 0.95; P = 0.001). The cross-reactivity of the C. pneumoniae-positive sera with C. trachomatis- and C. psittaci-positive sera was assessed for each MIF kit. For C. pneumoniae-positive sera with titers of > or =32, the Labsystems MIF kit exhibited more cross-reactivity to C. psittaci than the MRL kit did. The values obtained with the Labsystems EIA kit represented single dilutions of serum specimens expressed as enzymeimmuno units on a continuous scale. The results obtained with the Labsystems EIA kit correlated moderately well with those obtained with each MIF kit when they were compared for their abilities to detect IgG antibodies to C. pneumoniae (for the MRL MIF kit, r = 0.79 [P = 0.001]; for the Labsystems MIF kit, r = 0.78 [P = 0.001]). The results obtained with the commercial MRL and Labsystems MIF kits and the Labsystems EIA kit tested were reproducible; and the kits were standardized, had quality control reagents, and are suitable for detection of C. pneumoniae antibodies in serum and for use in interlaboratory studies. Validation of the use of these kits for clinical diagnosis still needs further evaluation.     

Three-year study of antibody toBorrelia burgdorferi in Southern Spain

The prevalence of anti-Borrelia burgdorferi antibodies was studied in Granada, Spain, between January 1991 and November 1993 in 354 patients with suspected Lyme disease (group 1); in 50 patients either with syphilis (n=32) or without syphilis but with a positive Rapid Plasma Reagin test (n=18) (group 2); and in 150 healthy subjects (group 3). In addition, intrathecal antibody production was evaluated by EIA in CSF samples obtained from 117 patients in group 1. Anti-Borrelia burgdorferi antibodies were detected by EIA in 58 patients (16.4 %) in group 1, 29 (8.2 %) of whom were positive by Western blot. Intrathecal antibody production was detected in one patient. In group 2, 8 (16 %) patients had a positive EIA result, but none of these was confirmed by Western blot. Western blot was negative for all subjects in group 3. The results of this study indicate that anti-Borrelia burgdorferi antibodies are not uncommon in our area, although Lyme disease is rare.     

Evaluation of the performance of commercial test kits for detection of Helicobacter pylori antibodies in serum.

We have compared the sensitivities, specificities, and predictive values of three commercial serological assays for the diagnosis of Helicobacter pylori infection. A qualitative latex method (Pyloriset; Orion Diagnostics), a semiquantitative enzyme-linked immunosorbent assay (ELISA) (GAP test IgG; Bio-Rad), and a quantiative ELISA (Helico-G; Porton Cambridge) were used in 109 untreated dyspeptic patients. The presence of H. pylori was established when the results of culture and/or histology of the gastric biopsies taken were positive. The prevalence of H. pylori infection was 62% (52% in 42 patients younger than 45 years of age and 69% in 67 patients older than 45 years of age). Sensitivities and specificities were 68 and 76% for Pyloriset, 89 and 77% for GAP test IgG, and 82 and 83% for Helico-G. The positive predictive values for all three tests were between 85 and 90%. The predictive values for the absence of disease with a negative result were 62, 82, and 74% for Pyloriset, the GAP test, and Helico-G, respectively. With Helico-G in the younger group (less than 45 years), sensitivity significantly lower (71 versus 87%) and a positive predictive value lower than those for the older group (greater than 45 years) were found. Either the sensitivities and specificities of commercial methods for the measurement of antibodies to H. pylori in serum must be improved or the relationship between the presence of antibodies and the presence of bacteria in the stomach at the time of investigation is too weak to allow the use of serological techniques instead of culture and histological investigation of gastric biopsy material.     

Prevalence of antibodies toBorrelia burgdorferi in forestry workers and blood donors from the same region in Switzerland

Sera from 259 forestry workers and 100 blood donors in the Canton of Solothurn, Switzerland, were tested for IgG antibodies toBorrelia burgdorferi in two EIAs using as antigen either sonic extract of whole organisms or purified flagella. Applying a 95% specific cut-off value based on results in the sera of 100 blood donors, 86 (33%) and 91 (35%) of the forestry workers respectively showed an elevated specific IgG level in the two EIAs. None of the 259 forestry workers had clinical signs of active infection at the time blood was taken, and only nine could recall experiencing erythema-migrans-like skin lesions within the last ten years. Thus, asymptomatic infections must be frequent. Elevated specific antibody levels increased significantly with the age of the forestry workers (p<0.0001) and the duration of occupational exposure to ticks (p=0.0001). Thus serological results in individuals with high exposure to ticks must be interpreted with caution in view of the high a priori prevalence of antibodies toBorrelia burgdorferi in such persons. The prevalence of antibody to theBorrelia burgdorferi flagellum in a control population not selected for tick exposure, in this case blood donors, seems to be independent of geographical origin.     

Comparison of commercial serological tests for detection of Helicobacter pylori antibodies.

Serological testing for Helicobacter pylori infection is one of the diagnostic methods of choice. Various commercial kits that use different antigens have been developed, but data on their diagnostic accuracy and direct comparisons between the tests are lacking. We aimed to evaluate the sensitivity, specificity, and predictive value of three immunoglobulin G enzyme-linked immunosorbent assay kits: Pylori stat, Helico-G, and Premier H. pylori. Serum samples and gastric biopsy findings from 76 patients were evaluated. We found by using a priori cutoff values that the Pylori stat, Helico-G, and Premier kits had overall sensitivities of 96, 96, and 88%, respectively, and specificities of 94, 86, and 96%, respectively, compared with gastric biopsy findings. For 232 serum samples, the Pylori stat test and a previously validated standard serological assay on which the test was based disagreed in 3% of the cases, while for 76 samples that were tested, Helico-G and a previously validated standard assay on which it was based disagreed in 8% of the cases. The intra- and interassay precision of each of the test kits was high. We conclude that serology based on any of these commercial tests represents a reliable and valid method for the diagnosis of H. pylori whether or not highly purified antigens are used.     

四种乙肝病毒表面抗原ELISA诊断试剂的评价

目的 对四种国内乙肝病毒表面抗原诊断试剂进行评价。方法 用四种试剂分别对标准品和未知血清进行检测，用几种常用诊断试验评价方法对检测结果进行分析和比较。结果 四种试剂对标准血清的检测结果较好，A、B两种试剂的总符合率为100％，另两种的总符合率也在90％以上，其中B试剂有较好的精密性。δ值比较显示A和B两种试剂有较好的诊断特性。四种试剂在一定的抗原浓度范围内都有良好的线性关系。针对于未知样本的检测中，四种试剂与采用电发光法的罗氏诊断试剂有较好的一致性。结论 国内主要厂家的HBsAg ELISA诊断试剂具有较高的检测效能。在实际工作中，可以通过常用的诊断试剂筛选实验，经统计分析后筛选出较高效能诊断试剂用于检测。     

Evaluation of five commercial kits to detect dsDNA antibodies.

Experiments were performed to evaluate five commercial kit assays used for the detection of antibodies to dsDNA. The kits were compared using a performance index score as recommended by the guidelines of the European Committee for Clinical Laboratory Standards. The highest performance score was obtained using the radioimmunoassay from Immunodiagnostic Services Ltd, with the Amersham kit second, the immunofluorescence test using Crithidia luciliae third, the Walker ELISA kit fourth, and the haemagglutination assay fifth. The results showed that none of the kits was outstanding, each appeared to detect a different anti-DNA antibody type as different results were obtained using each kit in assays of quality control sera, linearity of the method, antibody detection in various patient groups, and interference by various substances. It is suggested that laboratories using commercial assay kits for the detection of antibodies to dsDNA should decide which is the most appropriate to their particular needs and that a performance index scoring system may be useful in the comparison of assay evaluations between different laboratories.     

Comparison of five different immunoassays for the detection of Borrelia burgdorferi IgM and IgG antibodies

The performances of five commercially available enzyme immunoassays were compared for the detection of Borrelia burgdorferi IgM and IgG antibodies. Sensitivity was assessed with European serum samples collected from 45 patients with clinically defined Lyme disease in conjunction with a positive immunoblot (n = 44) or other serological test (n = 1). Sensitivities for the detection of IgM and IgG with each test were: Dako IgM 64%; Dako IgG 53%; Serion IgM 89%; and Serion IgG 88%. The Immunetics assay makes no distinction between IgM and IgG antibodies and had a sensitivity of 91%. Specificity was calculated by testing a control group comprising 40 patients with acute Epstein-Barr virus infection, cytomegalovirus infection, syphilis or rheumatoid factor positivity. The specificities achieved for each test were: Dako IgM 78%; Dako IgG 100%; Serion IgM 52%; Serion IgG 92%; and Immunetics 92%. The discriminatory power between control and patient samples appeared highest for the Immunetics assay. Between-run variation was comparable for the five tests and did not exceed 13%. When the Immunetics assay was used as an initial screening test, with low-titre positive results confirmed by an immunoblot, a sensitivity of 91% and a specificity of 100% were achieved. To attain maximal sensitivity, the Serion IgM and IgG tests were also performed on samples with negative Immunetics results. All positive Serion IgM and IgG results were also confirmed by immunoblot. In conclusion, the Immunetics assay, based on a synthetic C6 peptide, can be used reliably as an initial screening test for the serodiagnosis of Lyme disease.     

Evaluation of EIA kits for the detection of HIV antibodies

We compared four commercially available enzyme immunoassay (EIA) kits for the detection of HIV antibodies using immunoblot analysis as a confirmatory test. The kits gave satisfactory results as far as sensitivity and specificity are concerned as required for the use in the laboratories of blood banks. For the sera of patients on haemodialysis, haemophiliacs, patients "under observation" for AIDS and homosexuals the results obtained by Behring and Organon kits were less satisfactory, as the number of false positive results was much higher than with kits produced by Genetic and Wellcome. The frequency of false negative results was small in the tests using Organon and Genetic kits, while using Behring and Wellcome kits no false negative results were found.     

An evaluation of three commercial kits for use as screening methods for the detection of leptospiral antibodies in the UK

AIMS: To compare three commercial screening tests--the PanBio leptospiral IgM enzyme linked immunosorbent assay (ELISA), the Biolisa leptospiral IgM ELISA, and the indirect haemagglutination assay (IHA)--with the microscopic agglutination test (MAT) and two "in house" ELISAs--urease and horseradish peroxidase (HRP)--for the detection of leptospiral antibodies in a local UK and Eire population. METHOD: Two hundred sera submitted for a differential diagnosis of leptospirosis were tested by all methods. A further 142 sera from patients with antibodies to toxoplasma, Epstein-Barr virus (EBV), hepatitis A virus, rheumatoid factor, Borrelia burgdorferi, Mycoplasma pneumoniae, syphilis, cytomegalovirus, and Q fever were tested for crossreactivity. RESULTS: Compared with the MAT, sensitivity and specificity were found to be: PanBio, 90%/94%; Biolisa with sorbent, 100%/85%; and IHA, 54%/95%. Seven of 200 trial sera gave false negative results with PanBio; 14 of 200 trial sera gave false positive results with Biolisa with sorbent, as did a further 25 of the 142 sera tested for potential crossreactivity. Two of 142 sera gave crossreactions with PanBio and IHA (one each). CONCLUSIONS: The degree of false positivity seen with the Biolisa suggests that the recommended positive value of > or = 26 Eu/ml should be reassessed using pools of sera from local populations. When the cut off value was reassessed, using a value of > or = 40 Eu/ml, a sensitivity and specificity of 96% and 94%, respectively, was achieved. Even the modified Biolisa appears to be over sensitive and to show a high degree of non-specificity. The IHA, although specific (95%), lacked sensitivity in this study. The PanBio appeared to be the most suitable as a screening test for leptospiral IgM in the UK, although it would be advisable for all positive test results to be confirmed by a different enzyme immunoassay and the MAT.     

Comparison of five commercial serological tests for the detection of anti-Chlamydia trachomatis antibodies

Screening for Chlamydia trachomatis-specific antibodies is valuable in investigating recurrent miscarriage, tubal infertility and extrauterine pregnancy. We compared here the performance of immunofluorescence (IF) to four other commercial tests in detecting IgG antibodies directed against C. trachomatis: two enzyme-linked immunosorbent assays (ELISAs) using the major outer membrane protein (MOMP) as the antigen, commercialised respectively by Medac and R-Biopharm (RB), one ELISA using the chlamydial heat shock protein 60 (cHSP60) as the antigen (Medac), as well as a new automated epifluorescence immunoassay (InoDiag). A total of 405 patients with (n = 251) and without (n = 154) miscarriages were tested by all five tests. The prevalence of C. trachomatis-specific IgG antibodies as determined by the IF, cHSP60-Medac, MOMP-Medac, MOMP-RB and InoDiag was 14.3, 23.2, 14.3, 11.9 and 26.2%, respectively. InoDiag exhibited the highest sensitivity, whereas MOMP-RB showed the best specificity. Cross-reactivity was observed with C. pneumoniae using IF, MOMP-RB and InoDiag, and Parachlamydia acanthamoebae using the cHSP60 ELISA test. No cross-reactivity was observed between C. trachomatis and the other Chlamydiales (Neochlamydia hartmannellae, Waddlia chondrophila and Simkania negevensis). Given its high sensitivity, the new automated epifluorescence immunoassay from InoDiag represents an interesting alternative. The MOMP-based ELISA of R-Biopharm should be preferred for large serological studies, given the high throughput of ELISA and its excellent specificity.