Direct appraisal of latex agglutination testing, a convenient alternative to enzyme immunoassay for the detection of rotavirus in childhood gastroenteritis, by comparison of two enzyme immunoassays and two latex tests.

During February and March 1984, 207 fecal samples from infants and children with gastroenteritis were tested for rotavirus with four techniques: two enzyme immunoassays (Rotazyme; Abbott Laboratories, North Chicago, Ill., and Enzygnost-Rotavirus; Calbiochem-Behring, La Jolla, Calif.) and two latex agglutination tests (Rotalex; Orion Research, Inc., Cambridge, Mass., and Slidex Rota-Kit; Biomérieux). All stool samples were also tested for yeasts and bacterial pathogens. Electron microscopy was used to investigate discrepant results. We found 47% positive samples with Enzygnost-Rotavirus, 38% with Rotazyme, 37% with Slidex Rota-Kit, and 34% with Rotalex. No specimen was found positive by Rotazyme only or Slidex Rota-Kit only. On the contrary, 12 samples which were positive with Enzygnost-Rotavirus only and 3 which were positive with Rotalex only were not confirmed as positive by electron microscopy. Both enzyme immunoassays gave 6% equivocal results; Slidex Rota-Kit gave significantly fewer equivocal results than did Rotalex: 2.9% versus 9.7% (P less than 0.01). The sensitivity and specificity of latex tests compared favorably with that of enzyme immunoassays. Latex agglutination tests can be performed by unskilled personnel and are rapid and relatively cheap. They appear to be very suitable for routine laboratory work and may prove useful for large-scale screening in developing countries.     

Comparison of six serological assays for human immunodeficiency virus antibody detection in developing countries.

Three commercially available assays for the detection of human immunodeficiency virus (HIV) antibodies-Vironostika enzyme immunoassay (EIA), Wellcozyme competitive EIA, and JLC Allaman indirect immunofluorescence assay--were tested on 300 serum samples from African subjects with and without HIV-related conditions. Two experimental assays both rapid and simple to perform (Biotech dip stick and Cambridge Bioscience latex agglutination) were also evaluated on the same serum samples. The results were compared with those of a commercial Western blot (WB) (immunoblot) assay from Biotech, used as the reference technique. All assays were tested in the laboratory of the AIDS Project in Kigali, Rwanda. Calculated specificity ranged from 90.8% (dip stick) to 98.6% (Vironostika EIA, Wellcozyme competitive EIA, and Cambridge Bioscience latex agglutination). Sensitivity ranged from 95.2% (Cambridge Bioscience latex agglutination) to 98.0% (Vironstika EIA) and JLC indirect immunofluorescence assay). However, the sensitivity of the latex agglutination test improved to 98.6% after the prozone effect was controlled for by serial twofold dilution of latex agglutination-negative, WB-positive samples. In situations with a high prevalence of HIV infection, any one of these tests can be regarded as an alternative to the more expensive, time-consuming, and difficult WB assay.     

Comparison of nine commercial immunoassays for the detection of rotavirus in fecal specimens.

One hundred fecal specimens obtained from patients with acute gastroenteritis were tested for rotavirus with nine commercial immunoassays to evaluate the sensitivity, specificity, predictive value, and diagnostic accuracy of these assays. Kits evaluated included two monoclonal antibody-based enzyme immunoassays (EIAs) (Rotaclone and Pathfinder Rotavirus), three polyclonal antibody-based EIAs (Rotavirus Immunoassay, Rotazyme II, and Wellcozyme Rotavirus), and four latex agglutination assays (Rotastat, Virogen Rotatest, Meritec-Rotavirus, and The Wellcome Latex Test). Thirty-eight of the 100 specimens were found to contain rotavirus by a reference microplate EIA. The accuracy of the reference assay was determined by RNA electrophoresis and a blocking assay on discordant specimens. The two monoclonal antibody EIAs had superior sensitivities (100%) and identified two positive specimens which were negative by the reference method but positive by the blocking assay. Among the polyclonal EIAs, all had sensitivities of greater than 90%, but specificities were variable; Rotazyme II, with a specificity of 50%, showed considerable discrepancy from other polyclonal EIAs. The latex tests had sensitivities ranging from 70 to 90% and specificities of 80 to 100%. Latex agglutination tests were more rapid than EIAs and did not require expensive equipment. The final choice of assay system will depend on the cost, speed, and accuracy requirements of the clinical laboratory.     

Evaluation of two commercial enzyme immunoassays for the detection of norovirus in faecal samples from hospitalised children with sporadic acute gastroenteritis

Two commercially available enzyme immunoassays (EIAs), IDEIA and Ridascreen, for norovirus antigen detection were evaluated with 117 faecal samples from hospitalised children with acute gastroenteritis. Eighteen of 39 samples positive by RT-PCR were characterised by sequence analysis, and 17 of these were related to norovirus genogroup II. When compared with RT-PCR, the sensitivity and specificity values were 76.9% and 85.9%, respectively, for the IDEIA assay, and 59.0% and 73.1%, respectively, for the Ridascreen assay. The sensitivity and specificity of both EIA tests require improvement, but they could both eventually be of use in the diagnosis of norovirus diarrhoea in clinical laboratories.     

Comparison of enzyme-immunoassay and radioimmunoassay for detection of human rotaviruses and adenoviruses from stool specimens

An enzyme-immunoassay (EIA) using polystyrene beads as the solid phase, guinea pig anti-rotavirus or anti-adenovirus immunoglobulin as primary antibody, rabbit anti-rotavirus or anti-adenovirus immunoglobulin as secondary antibody, and horseradish peroxidase-conjugated swine anti-rabbit immunoglobulin as indicator antibody, has been developed for the detection of human rotavirus and adenovirus antigens from stool specimens. A comparison of the developed EIA and radioimmunoassay (RIA) used previously in our laboratory was made with 250 stool specimens from children with acute gastroenteritis. Two specimens were found negative by both rotavirus and adenovirus EIAs but not by RIAs, but in each of these cases confirmatory EIA tests showed them to be false negatives. The confirmatory EIA tests were also necessary in several cases to prove the specificity of the binding or to eliminate non-specific reactions with specimens giving low positive reactions in EIA. The developed EIA was found to be as specific, sensitive and reliable as RIA in the routine diagnosis of rotavirus and adenovirus gastroenteritis provided that appropriate confirmatory tests were included.     

A practical single sample dry latex agglutination test for Helicobacter pylori antibody detection.

Assessment of a single serum sample for Helicobacter pylori antibodies is frequently requested in routine diagnostic laboratories. Current enzyme linked immunosorbent assay (ELISA) kits are not ideal for testing small numbers of serum samples and some have low sensitivities, specificities or large grey zones. A panel of 90 serum samples from patients who had presented for routine upper endoscopy was used to compare three kits for the detection of H pylori antibodies: (1) Pyloriset Dry, total antibody latex agglutination, Orion Diagnostica, Espoo, Finland; (2) Pyloriset enzyme immunoassay (EIA), IgG ELISA, Orion; and (3) Hel-p, IgG ELISA, Amrad, Kew, Victoria, Australia. Diagnosis of H pylori positivity was made if culture results and either rapid urease test or histopathology were positive. The sensitivity, specificity, positive, and negative predictive value for each test was as follows: Orion: latex 93.3%, 95.6%, 95.5%, 93.3%, respectively; Orion: EIA-G 84.4%, 97.8%, 97.4%, 84.4%, respectively; and Amrad: EIA-G 100%, 88.9%, 90%, 100%, respectively. The latex test performed better than the EIAs with respect to sensitivity and specificity.     

Comparison of Four Assays for the Detection of Cryptococcal Antigen

We compared the performance of four assays for the detection of cryptococcal antigen in serum samples (n = 634) and cerebrospinal fluid (CSF) samples (n = 51). Compared to latex agglutination, the sensitivity and specificity of the Premier enzyme immunoassay (EIA), Alpha CrAg EIA, and CrAg lateral flow assay (LFA) were 55.6 and 100%, 100 and 99.7%, and 100 and 99.8%, respectively, from serum samples. There was 100% agreement among the four tests for CSF samples, with 18 samples testing positive by each of the assays.     

Reactivity of serologic tests for the detection of antibody specific to cytomegalovirus. II. Latex agglutination and enzyme-linked immunosorbent assay

Two hundred seven sera were assayed for antibody-specific for cytomegalovirus (CMV) by two enzyme immunoassays (EIAs; Bioenzabody, Litton Bionetics, and Abbott CMV Total Antibody EIA, Abbott Laboratories) and latex agglutination (LA; CMVScan, Hynson, Westcott and Dunning). The overall accuracy of the LA, Litton EIA, and Abbott EIA was 95.8%, 86.2%, and 88.6%, respectively. Although the Abbott EIA had a sensitivity of 98.8%, the specificity was only 35.5%. The positive predictive values of the LA, Litton EIA, and Abbott EIA were 99.4%, 95.9%, and 88.9%, respectively, while the negative predictive values of each of these tests were 81.1%, 56.2%, and 84.6%, respectively.     

Clostridium difficile is not associated with outbreaks of viral gastroenteritis in the elderly in the Netherlands

The coincidental increase in norovirus outbreaks and Clostridium difficile infection (CDI) raised the question of whether these events could be related, e.g. by enhancing spread by diarrhoeal disease outbreaks. Therefore, we studied the prevalence of C. difficile in outbreaks of viral gastroenteritis in nursing homes for the elderly and characterised enzyme immunoassay (EIA)-positive stool samples. Stool samples from nursing home residents (n = 752) in 137 outbreaks of viral aetiology were investigated by EIA for the presence of C. difficile toxins. Positive samples were further tested by a cell neutralisation cytotoxicity test, a second EIA and culture. Cultured isolates were tested for the presence of toxin genes, the production of toxins and characterised by 16S rRNA polymerase chain reaction (PCR) and sequencing. Twenty-four samples (3.2%) tested positive in the EIA. Of these 24 positive samples, only two were positive by cytotoxicity and three by a second EIA. Bacterial culture of 21 available stool samples yielded a toxinogenic C. difficile PCR ribotype 001 in one patient sample only. In conclusion, we found no evidence in this retrospective study for an association between viral gastroenteritis outbreaks and C. difficile. The high rate of false-positive EIA samples emphasises the need for second confirmation tests to diagnose CDI.     

ImmunoCard STAT! cartridge antigen detection assay compared to microplate enzyme immunoassay and modified Kinyoun's acid-fast staining technique for detection of Cryptosporidium in fecal specimens

Cryptosporidium species infect humans and a wide range of animals worldwide; outbreaks of cryptosporidiosis have been reported in several countries. Routine diagnostic methods may be insufficient to demonstrate the presence of these organisms. The study assessed the diagnostic accuracy of the antigen detection immuno-cartridge test, ImmunoCard STAT! (Meridian Bioscience Inc., Cincinnati, OH, USA), compared to the combined gold standard: modified Kinyoun's acid-fast technique confirmed with the microplate enzyme immunoassay (EIA) for the detection of Cryptosporidium in fecal specimens. Three hundred fifteen formalin-fixed stool specimens were submitted for testing. The Kinyoun's acid-fast-stained smear revealed 24 positive samples for Cryptosporidium (of which 23 specimens were confirmed by the EIA) and 291 negative samples (of which 289 were negative by EIA). Agreement between the three used tests was shown in 22 positive and 288 negative samples for Cryptosporidium. Kappa score of agreement between the immuno-cartridge test and EIA was 0.957, p?=?0.000. The sensitivity of the immuno-cartridge test was 96% (95% confidence interval (CI), 87% to 104%) and the total accuracy of the test was 97% (95% CI, 93-103). The ImmunoCard STAT! Cryptosporidium cartridge assay is easy to use and does not require specialized training or equipment and is useful in routine diagnosis and screening for Cryptosporidium especially where rapid, point of care testing is needed or where other reliable tests are unfeasible with a performance comparable to the EIA and acid-fast technique.     

Status and significance of testing for hepatitis B surface antigen and surface antibody

Following Blumberg's discovery of hepatitis B surface antigen (HBsAg), many attempts have been made to develop several in vitro diagnostic techniques for the detection of this antigen and its homologous antibody. The two-dimensional micro-Ouchterlony immunodiffusion has been the first technique used, rapidly replaced by procedures of increasing sensitivity characterized as second-generation and the currently available third-phase tests which include radioimmunoassay (RIA), reverse passive haemagglutination (RPHA), reverse passive latex agglutination (RPLA) and enzyme immunoassay (EIA). Among these, RIA appears to be the most sensitive and specific, whereas EIA, RPHA and RPLA have the advantage of long shelf-life of stable reagents, no need for sophisticated and expensive equipment and no hazard associated with the handling of radioactive isotopes. Moreover, the sensitivity of EIA should increase by objective reading with a colorimeter.The most sensitive method for the detection of surface antibody (anti-HBs) is again RIA, whereas passive haemagglutination (PHA) had the advantage of providing titres. Finally EIA, based on inhibition of a known amount of HBsAg, has at least the same sensitivity as PHA, but has the advantage that reagents are more stable and that it permits screening for both HBsAg and anti-HBs with the same reagents at the same time. The application of these highly sensitive techniques for the detection of HBsAg and anti-HBs has resulted in a consistent reduction in the incidence of post-transfusion hepatitis type B and in a better understanding of the aetiology, epidemiology and natural history of this infection.     

Comparison of three serological methods for diagnosing Mycoplasma pneumoniae infection.

AIMS--To compare the novel Serofast latex agglutination test (International Mycoplasma, Toulon-Cedex, France) with the complement fixation test and enzyme immunoassay (EIA) for diagnosing acute Mycoplasma pneumoniae infection. METHODS--Paired sera from 60 patients with respiratory infection who had tested positive for M pneumoniae by complement fixation test were analysed with Serofast and indirect EIA for specific IgG and IgM antibodies. RESULTS--Serofast was less sensitive than the two other tests. Only 30 (50%) out of 60 paired sera which showed a diagnostic seroconversion or had high positive, unchanged antibody titres by complement fixation test or EIA, or both, tested positive with Serofast. Positive test results with Serofast were associated with the presence of a complement fixation test titre of > or = 512 and high positive IgM antibody titres measurable by EIA; virtually all patients with a complement fixation test titre of < 256 or those responding primarily in the IgG class tested negative with Serofast. Based on analysis of sera taken at the acute phase of infection, 10 (17%) of the 60 patients tested positive by complement fixation test, 10 (17%) by EIA, and only four (7%) by Serofast. CONCLUSIONS--Serofast was less sensitive than complement fixation test and EIA and it cannot be recommended as a replacement for either test in routine diagnostic use. It might prove useful in laboratories where non-specific tests, such as the determination of cold agglutinins, are still used for the diagnosis of M pneumoniae infection. Testing paired sera is, however, a prerequisite for obtaining acceptable sensitivity by Serofast as well as other serological methods currently available.     

Comparison of latex agglutination with enzyme immunoassay for detection of rotavirus in fecal specimens

Human rotaviruses are the most important etiologic agents of acquired diarrhea in infants and young children worldwide. Early diagnosis is essentialfor effective patient treatment. The latex agglutination (LA) assays for rotavirus diagnosis are rapid, inexpensive, and the most widely used to screen specimens. The performance of the LA Rotagen (Biokit S.A., Barcelona, Spain) was evaluated for rotavirus detection infecal samples of outpatients with acute gastroenteritis. This assay was compared with the enzyme immunoassay (EIA) EIARA (Bio-Manguinhos, Rio de Janeiro, Brazil). From January to October 2000, 285 fecal specimens were analyzed. Forty-four samples (15.4%) were reactive, 214 (75.4%) were nonreactive, and 27 (9.5%) were indeterminate by LA. All LA-positive samples were positive by EIA, and 2 LA-negative samples were positive by EIA. Of specimens indeterminate by LA, 67% were positive by EIA. The sensitivity, specificity, and accuracy of LA were 69%, 100%, and 93%, respectively. These results indicate that assay is as sensitive and specific as the EIA, and it could be applied on a large scale for screening stool specimens in suspected rotavirus diarrhea. However, the indeterminate results must be confirmed by other methods, such as EIA.     

Evaluation of the CMV-CUBE assay for detection of cytomegalovirus serologic status in marrow transplant patients and marrow donors.

We evaluated a new membrane dot immunobinding assay (CMV-CUBE; Difco Laboratories) for the detection of cytomegalovirus (CMV) antibody in marrow transplant patients and donors. The CMV-CUBE assay was compared with a commercially available enzyme immunoassay (EIA; CMV STAT) and a latex agglutination (LA; CMVScan) test. Serum samples were collected from 311 transplant patients and donors prior to transplantation. A total of 164 serum specimens were positive for CMV antibody by one or more of the three assays, with 153 of 164 samples (93.3%) positive by all three tests. A total of 147 serum specimens were CMV antibody negative. CMV-CUBE detected 154 of 164 (94%) of the positive samples, EIA detected 160 of 164 (97.5%), and LA detected 157 of 164 (95.7%) CMV-positive samples. Compared with EIA, CMV-CUBE had a sensitivity of 95.6% and a specificity of 99.3%. Compared with LA, CMV-CUBE had a sensitivity of 97.5% and a specificity of 99.4%. CMV-CUBE is a simple and rapid visual assay which can be used for the qualitative detection of antibody to CMV in patient serum.     

Detection of cytomegalovirus antibody with latex agglutination.

Transfusion-acquired cytomegalovirus (CMV) infections should be prevented in seronegative immunocompromised patients by providing blood products from donors who are also seronegative. Latex agglutination was investigated as a simple and rapid method for detecting antibody against CMV. Latex beads were coated with CMV antigen, incubated for 8 min at room temperature with 25 microliter of sera, and examined for agglutination. The sensitivity and specificity of latex agglutination was compared with that of indirect hemagglutination (IHA, Cetus Corp., Emeryville, Calif.) and enzyme immunoassay (EIA) with sera from 604 random blood donors or patients. Of 327 serum samples shown to be seronegative by EIA and IHA, 327 had a latex agglutination titer of less than 1:4 (specificity, 100%). Of 236 serum samples with detectable antibody by EIA and IHA, 228 had a latex agglutination titer of 1:4 or greater (sensitivity, 97%). Plasma collected with EDTA, heparin, or citrate was satisfactory for latex agglutination. Latex agglutination results correlated quantitatively with those of EIA, and the test also detected fourfold or greater rises in antibody with paired sera from six patients with posttransfusion CMV infections. Latex agglutination is a sensitive and specific assay that is rapid and simple to perform and should be effective in selecting seronegative blood donors to prevent posttransfusion CMV infections in seronegative recipients.     

Recombinant antigen-based enzyme immunoassay for screening of Treponema pallidum antibodies in blood bank routine.

This work reports a comparison of an enzyme immunoassay (EIA) using two major Treponema pallidum recombinant antigens with a T. pallidum hemagglutination (TPHA) assay and a nontreponemal Venereal Disease Reference Laboratory (VDRL) test. A total of 1,822 normal donor serum samples was tested for cardiolipin and T. pallidum antibodies, respectively, by the VDRL assay and EIA. Among these samples, 440 were further tested by TPHA technology. Four samples were found positive by EIA, while all were reported to be negative by both TPHA and VDRL routine assays. Subsequent testing of EIA-positive samples confirmed 100% (four of four samples) and 25% (one of four samples) positive results, respectively, by immunofluorescence assay and a Western blot (immunoblot) syphilis kit. The sensitivity of the recombinant EIA was estimated at virtually 100% with a reference panel of 50 syphilitic samples. According to this study, the newly developed EIA kit shows 100% sensitivity combined to a specificity greater than 99.8% for detecting treponemal immunoglobulin G antibodies in blood bank syphilis screening.     

Enzyme Immunoassay versus Latex Agglutination Cryptococcal Antigen Assays in Adults with Non-HIV-Related Cryptococcosis

We compared paired enzyme immunoassay (EIA) and latex agglutination (LA) assay results with 185 blood and 164 cerebrospinal fluid (CSF) samples from 44 and 33 non-HIV cryptococcosis patients, respectively. The LA assay cutoff of 1:256 in the blood and 1:32 in the CSF was most highly predictive of a positive EIA result. The EIA missed 18.4% detected by the LA assay in the blood samples and 7.8% detected by the LA assay in the CSF samples. We note here the improved sensitivity of the LA assay over the EIA in non-HIV patients.