Evaluation of screening tests for the detection of antistreptolysin O antibodies

The accuracy of two screening tests, one utilizing serum and the other utilizing whole blood, was compared with the accuracy of the conventional macrotitration method for the detection of antistreptolysin O antibodies. Of the 569 specimens tested with the serum screening procedure and the macrotitration method, 235 and 282, respectively, were positive for antistreptolysin O antibodies. Comparative testing of 200 specimens with the peripheral blood screening test and the macrotitration method gave 60.5% by the macrotitration procedure. Discrepant results with both procedures were obtained with specimens having 166 Todd units. The results suggest that these screening procedures can be used to screen specimens for the presence of significant antistreptolysin O antibodies.     

Evaluation of 12 commercial tests for detection of Epstein-Barr virus-specific and heterophile antibodies

Ten microbiological departments in Norway have participated in a multicenter evaluation of the following commercial tests for detection of Epstein-Barr virus (EBV)-specific and heterophile antibodies: CAPTIA Select viral capsid antigen (VCA)-M/G/EBNA (Centocor Inc.), Enzygnost anti-EBV/immunoglobulin M (IgM) and IgG (Dade Behring), Vironostika EBV VCA IgM/IgG/EBNA enzyme-linked immunosorbent assay (ELISA) (Organon Teknika), SEROFLUOR immunofluorescence assay and EBV Combi-Test (Institute Virion Ltd.), anti-EBV recombinant IgM- and IgG-early antigen/EBNA IgG ELISA (Biotest Diagnostics), EBV IgM/IgG/EBNA ELISA (Gull Laboratories), Paul-Bunnell-Davidsohn test (Sanofi Diagnostics Pasteur), Monosticon Dri-Dot (Organon Teknika), Avitex-IM (Omega Diagnostics Ltd.), Alexon Serascan infectious mononucleosis test (Alexon Biomedical Inc. ), Clearview IM (Unipath Ltd.), and Cards+/-OS Mono (Pacific Biotech, Inc.). The test panel included sera from patients with primary EBV infection, immunocompromised patients with recent cytomegalovirus infection, healthy persons (blood donors), and EBV-seronegative persons. Among the tests for EBV-specific antibodies the sensitivity was good, with only small differences between the different assays. However, there was a greater variation in specificity, which varied between 100% (Enzygnost) and 86% (Biotest). Tests for detection of heterophile antibodies based on purified or selected antigen (Avitex, Alexon, Clearview IM, and Cards+/-OS Mono) were more sensitive than the Paul-Bunnell-Davidsohn and Monosticon tests.     

Evaluation of three commercial enzyme immunoassays for toxoplasma and cytomegalovirus antibodies.

Three commercially available enzyme immunoassays (EIAs) were evaluated for specificity and sensitivity compared to immunofluorescent assays (IFAs) for detection of IgG and IgM antibodies to Toxoplasma gondii (Toxo) and Cytomegalovirus (CMV). A panel of 78 sera were tested, including specimens known to contain Toxo IgG or IgM, CMV IgM or IgM, antinuclear antibodies (ANA), antimitochondrial antibodies (AMA), and rheumatoid factor (RF). Linear correlation analysis comparing EIA and IFA results showed that the statistical relationship between the two assay methods was relatively weak (correlation coefficients ranging from 0.33 to 0.86). Qualitative correlation showed that the EIA methods agreed with IFA results in most cases. One manufacturer's products (Diamedix Corp.) gave consistently better sensitivity, specificity, and intra-assay reproducibility values than the other two systems (Clinical Sciences, Inc., and Whittaker Bioproducts). ANA, AMA, and RF did not appear to interfere with any EIAs.     

Evaluation of three commercial agglutination tests for the identification of Staphylococcus aureus.

Three commercially available rapid slide agglutination tests for the identification of Staphylococcus aureus were evaluated with 354 recent clinical isolates (165 strains of S. aureus). The test results of two latex agglutination products, SeroSTAT Staph (Scott Laboratories, Inc.) and Staphylatex (American Micro Scan), and one hemagglutination product, Staphyloslide (BBL Microbiology Systems), were compared with the results of the tube coagulase test, which was read at 4 h (4-h tube coagulase test) and, if negative, again after overnight incubation at room temperature (24-h tube coagulase test). Discrepancies between agglutination and tube coagulase identifications were resolved by use of the thermonuclease, mannitol fermentation, and slide coagulase tests. All sensitivities, specificities, predictive values of a positive result, and predictive values of a negative result for the three agglutination tests were at least 98.8% and comparable with the 4-h tube coagulase test. Best results were obtained with the 24-h tube coagulase test, which yielded one false-negative and no false-positive tests. Agglutination identifications may be performed on organisms taken directly from a primary plate when sufficient growth is present. Kit agglutination procedures yield rapid and reliable identifications and are easy to perform. This study also demonstrates the usefulness of the 24-h tube coagulase test.     

Evaluation of five commercial assays for screening antenatal sera for antibodies to Toxoplasma gondii.

AIMS: To evaluate the suitability of five commercial assays (Toxoreagent, DA, Captia Toxo IgG, Toxenz-G, Toxonostika-G) for screening large numbers of sera for antibodies to Toxoplasma gondii. METHODS: Sera from 1000 pregnant women booking for antenatal care at a London hospital were screened in parallel by each test. Sera giving discordant results were retested. RESULTS: The Captia Toxo IgG enzyme immune assay gave the best specificity on initial screening, with 0/773 false positives and only 2/218 false negatives. The Toxoreagent latex agglutination test performed well provided sera were tested at several dilutions to prevent prozone effects; 0/218 false negatives (greater than 12 IU/ml). Only one evidently false positive result was seen in the 1000 samples tested. The DA test gave no false negative results but produced 23/773 false positives. After repeat testing there were 9/1000 sera which gave equivocal results which were negative by the Captia Toxo IgG test (less than 12 IU/ml) but with low titres of 16 in the Toxoreagent test or 4 IU/ml in the DA test. In this situation women would have been asked for a follow up sample for repeat testing. Only 300 sera were tested by Toxenz-G; initial screening produced 4/58 false negative results and 4/242 false positives. CONCLUSIONS: The Captia Toxo IgG test gave the fewest discordant results on initial screening. Results could be readily expressed in international units using a programmable plate reader, and this may be useful for epidemiological studies. The Toxoreagent test is considerably cheaper, and is a simple and reliable method for screening provided that at least two dilutions are used.     

Evaluation of eight commercial tests for Mycoplasma pneumoniae antibodies in the absence of acute infection

Eight commercially available tests for Mycoplasma pneumoniae (Serodia-Myco II, Labsystems IgM and IgG EIA, IgM and IgG LISA tests, ImmunoWell IgG test and SeroMP IgM and IgG) were compared using 204 single sera from healthy individuals. IgM peaked in late childhood and then declined, while IgG rose progressively into adulthood. Inter-assay agreement was poor. Positivity in Serodia-Myco II and LISA IgG was associated with blood group or Coombs positivity, suggesting non-specific reactions. The study confirmed that single serum serology is unsuitable for the diagnosis of M. pneumoniae infection, and that commercially available tests need further improvement.     

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.     

Evaluation of a latex agglutination test for screening antibodies to rubella virus

The performance of a commercial latex agglutination test for screening rubella antibodies was investigated, using two panels of selected serum samples especially designed for a careful evaluation of sensitivity. Three false negative results were obtained on samples with very low levels of antibody. However, the test had higher sensitivity than the hemagglutination inhibition test and fluoroimmunoassay when samples were tested undiluted. False positive results were not obtained, and prozone reactions were not observed. The test is a very practical method for screening rubella antibodies in primary health care units.     

Evaluation of two commercial tests for human immunodeficiency virus antigens in culture supernatant fluid

Two commercial enzyme-linked immunosorbent assays (EIAs) for human immunodeficiency virus (HIV) antigens were evaluated for sensitivity and reproducibility by use of supernatant fluid from cell cultures of peripheral mononuclear cells of 18 patients with acquired immunodeficiency syndrome (AIDS) and 12 asymptomatic HIV antibody-positive patients. Both commercial assays detected HIV antigen in all cultures by day 21; however, the Abbott HIV antigen EIA (Abbott Laboratories, North Chicago, IL) detected HIV antigen three to seven days earlier in 15 of 48 cultures (31%), on the same day in 32 cultures (67%), and three days later in 1 culture (2%) when compared with the DuPont HIV antigen EIA (DuPont Laboratories, Wilmington, DE). In serial twofold dilution experiments, the Abbott HIV Ag EIA was found to have at least a twofold to eightfold increased sensitivity over the DuPont assay. Repeat testing of 15 initially positive supernatant fluids by both assays revealed that 13 of 15 and 12 of 15 were consistently positive by the Abbott and DuPont assays, respectively. The authors conclude that the Abbott EIA demonstrated better performance in this study than the DuPont EIA for detection of HIV in cell culture because of its shorter time-to-positivity and greater sensitivity.     

Comparison of commercial diagnostic tests for Helicobacter pylori antibodies.

A number of serological tests measuring the presence of Helicobacter pylori-specific serum immunoglobulin G (IgG) are now commercially available. The aim of this study was to evaluate the clinical accuracy of five commercial H. pylori antibody tests: GAP-IgG (Biomerica), HELpTEST (AMRAD, Kew, Victoria, Australia), HELICO-G (Porton Cambridge), Pyloriset (Orion Diagnostica), and ROCHE (Roche Diagnostics). A total of 162 subjects presenting for routine upper endoscopy were studied. H. pylori was diagnosed if culture, histology, or both were positive. Ten milliliters of venous blood was collected at the time of endoscopy for serological assessment. The sensitivity and specificity of each test (GAP-IgG, HELpTEST, HELICO-G, Pyloriset, and ROCHE) were as follows: 83 and 79%, 92 and 77%, 86 and 65%, 89 and 56%, and 98 and 69%, respectively. Positive and negative predictive values were 97 and 83%, 90 and 91%, 76 and 83%, 68 and 84%, and 86 and 97%, respectively. The specificity of most tests increased by approximately 10% when sera from subjects less than 45 years old were examined. The number of sera falling into the grey zone for each test (an indeterminate result with respect to H. pylori status) varied between 2.5 and 19%. This study highlights the need for all serological kits to be independently evaluated on the population to be studied by testing against a microbiologically defined panel of H. pylori-positive and -negative sera.     

Evaluation of three rapid tests for detection of antibodies to HIV-1 non-B subtypes

Three rapid tests were evaluated for the detection of antibodies to HIV in 111 plasma specimens (81 HIV-1 non-B subtypes, including 4 coinfections with HIV-2, 30 HIV negative). The Determine HIV-1/2, Equipar HIV, and Multispot HIV-1/2 tests were 100% sensitive and specific for the detection of HIV-1 antibodies. Multispot showed 92.7% specificity for HIV-2.     

Evaluation of three immunoassays used for detection of anti-rubella virus immunoglobulin M antibodies

Three automated assays (Abbott AxSYM, Bayer ADVIA Centaur, and bioMerieux VIDAS) used for the detection of rubella virus-specific immunoglobulin M were evaluated. A total of 57 samples from individuals with evidence of infection with rubella virus were used to estimate sensitivity, and 220 samples from blood donors and individuals attending an antenatal clinic who had no evidence of recent infection were used to estimate specificity. Seroconversion panels comprising an additional 31 samples from four individuals were used to determine clinical sensitivity. Samples containing potentially cross-reacting substances were also tested. The sensitivities of the three assays ranged from 84.2 to 96.5%, and the specificities ranged from 96.8 to 99.9%. The Abbott AxSYM assay detected more reactive samples than the other two assays when a panel of 57 positive samples was tested. Bayer ADVIA Centaur detected more reactive samples in the seroconversion panels than the other two assays. All three assays evaluated reported a reactive result in 1 or more of the 48 samples containing potentially cross-reacting analytes. The assays demonstrated comparable performance in testing of a well-characterized panel of samples.     

Evaluation of a commercial anti-delta EIA kit for detection of antibodies to hepatitis delta virus

Anti-hepatitis delta virus (anti-HDV) antibodies were measured by solid phase IgG and IgM capture radioimmunoassays (RIA) as well as by a competitive binding enzyme immunoassay (EIA) in both acute and chronic HDV infections. EIA anti-delta test measures total delta antibody without discriminating IgM from IgG anti-delta. Low titer IgG antibodies were detected by both techniques with equal sensitivity. High titer IgG antibodies reached the end point sooner with EIA than with RIA (10(-3) versus greater than 10(-6)). When IgM anti-HDV was present without accompanying IgG anti-HDV, EIA failed to identify the antibody. Presence of high titer rheumatoid factor in the serum and lipemic samples produced false-positive results by EIA. Usage of undiluted serum samples for EIA probably exaggerates the factors contributing to false-positive reaction.     

Evaluation of five commercial tests for detection of immunoglobulin M antibodies to human parvovirus B19.

The following commercial tests for detection of immunoglobulin M antibodies to human parvovirus B19 were evaluated: Ideia Parvovirus B19-IgM, MRL Diagnostics Human Parvovirus B19 IgM ELISA, Parvoscan-B19, and Biotrin Parvo B19 IgM EIA and IF. A total of 203 serum specimens from patients who probably have current B19 infections or have other viral infections and sera with rheumatoid factor were investigated. Between 75 and 79 of 102 serum samples from patients thought to have current B19 infections yielded positive results with the different tests. Ideia had the highest specificity (94.8%), while Parvoscan showed a specificity of only 70.1%. Our evaluation results show that Ideia, MRL, and Biotrin EIA and IF can be recommended for diagnostic purposes.     

Evaluation of three commercial serological tests with different methodologies to assess Helicobacter pylori infection

The sera of 142 Helicobacter pylori-positive and 32 H. pylori-negative patients were assessed by a desktop test (QuickVue), an enzyme-linked immunosorbent assay (ELISA) (HM-CAP), and a solid-phase, two-step chemiluminescent enzyme immunoassay (Immulite). These tests yielded sensitivities of 97, 97, and 91% and specificities of 97, 94, and 100%, respectively. In conclusion, the desktop test and the ELISA are more sensitive than the chemiluminescent enzyme immunoassay (P < 0.05). The chemiluminescent enzyme immunoassay has the advantage that it is fully automated.     

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.