Discrepant toxoplasma latex agglutination test results.

The analysis of 4450 toxoplasma serology results showed that 59 (1.3%) latex agglutination reactions were not confirmed in the dye test. These discrepant results were associated with an unspecified IgM antibody but not associated with kit batch variation, inactivation of sera, concurrent cytomegalovirus infection, or the presence of hepatitis B virus "e" antigen. The latex agglutination test is useful as a screen for toxoplasma infection but false positive reactions do occur. Patients at risk of severe toxoplasmosis should be investigated by additional tests.     

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.     

Detection of rotavirus in faeces by latex agglutination

Human rotavirus (HRV) in faeces of patients may be readily detected with high sensitivity and specificity using latex agglutination (LA) on a glass slide by making use of the cross-reactivity of anti-calf rotavirus (CRV) antibody. Latex particles were coated with anti-CRV immunoglobin. The antibody coated particles (AC-L) are specifically agglutinated by both CRV and HRV, and the agglutination is evident macroscopically within a minute. To examine the sensitivity and reliability of the LA method compared to other methods, HRV in faecal extracts of 48 infants with acute gastroenteritis was sought by the LA, reversed passive haemagglutination (RPHA) and electron microscope (EM) methods. Samples positive by the EM method were all positive by the LA method, and samples negative by EM were all negative by LA. The LA method is suitable for application as a simple clinical diagnostic test.     

Detection of rinderpest antigen by latex agglutination test

A slightly modified latex agglutination test was applied for detection of rinderpest antigen. The antigen was added to sensitized latex particles in the presence of hyperimmune antiserum to facilitate agglutination. Out of 129 samples tested by latex agglutination (LA), solid phase aggregation of coated erythrocytes (SPACE), reverse phase passive haemagglutination (RPHA) and counter immunoelectrophoresis (CIE) test, 86.0, 86.8, 84.4 and 79.8 per cent, respectively, were found positive.     

Detection of typhus antibodies by latex agglutination.

A latex test for assay of antibodies to endemic and epidemic typhus rickettsiae is simple, group-specific, sensitive, and reproducible. Cross-reactivity within the typhus group was extensive.     

The determination of measles antibody titers in the latex agglutination reaction]

A new latex agglutination test (LAT) for detection of antibodies to measles virus in blood sera was developed. The latex diagnosticum consists of polymeric microspheres of national make carrying on their surface covalently bound measles virus antigen. The data on the specificity and sensitivity of the test are presented, and the results of titrations of blood sera from schoolchildren by traditional HI test and LAT are compared. LAT was shown to be highly sensitive, much simpler than the available methods for detection of measles antibodies and more economic, and therefore may be recommended for mass surveys.     

Detection of pneumococci in blood cultures by latex agglutination

Latex agglutination by use of the Pneumoslide test on clinical blood cultures detected 22 Streptococcus pneumoniae strains as the etiological agents in 47 streptococcal septic episodes. The other 25 isolates were identified as viridans streptococci or streptococci of groups A, B, D, or G. The test demonstrated 100% sensitivity, 92% specificity, and predictive values for positive and negative reactions of 91 and 92%, respectively. Two false-positive reactions were caused by strains of viridans streptococci. The two strains continued to give positive reactions when colonies from blood agar plates were tested according to the instructions of the manufacturer. This latex agglutination test is an effective tool for the rapid diagnosis of pneumococci in blood cultures.     

Biotin-labelled antigen screening test for toxoplasma IgM antibody.

A method for the simple preparation of biotin-labelled toxoplasma antigen was used with avidin peroxidase in an IgM-capture enzyme linked immunosorbent assay (BAM-ELISA). Although the overall predictive value of a positive result was only 38%, its low cost and 100% sensitivity makes it a very suitable screening test. Positive results can be confirmed by an alternative assay, thus providing a more economical and effective diagnostic service than either screening all sera by a commercial test or selecting sera for IgM testing.     

Detection of staphylococcal exfoliative toxin by slide latex agglutination.

A simple and rapid method in which slide latex agglutination was used was developed to detect the exfoliative toxin (ET) elaborated by clinical isolates. ET types A and B (ET-A and ET-B) were purified by plate gel isoelectrofocusing, and anti-ET sera were obtained by immunizing rabbits. A specific immunoglobulin G antitoxin was then prepared from the immunized rabbit sera by fast protein liquid chromatography, and latex particles were coated with the antitoxin. Of 74 staphylococcal strains isolated from patients with staphylococcal scalded skin syndrome, 61 strains were found to produce ET by the newborn mouse bioassay. All 61 strains were shown to be positive for ET-A and ET-B production by the slide latex agglutination method. The lowest concentration of ETs detected by the latex agglutination method was 0.5 microgram/ml, which was much lower than that detected by the double immunodiffusion method, with a sensitivity of 50 micrograms/ml. It is crucial to prove ET production by clinical isolates for the diagnosis and surveillance of staphylococcal scalded skin syndrome. The latex agglutination method is a sensitive, simple, and rapid test which can be used as an alternative to the newborn mouse bioassay.     

Detection of Legionella antigenuria by reverse passive agglutination.

A reverse passive agglutination method was developed to detect soluble antigens of Legionella spp. By this method Legionella antigens were detected in urine specimens from 14 of 15 antigenuric patients with clinically diagnosed Legionnaires disease and in none of 263 urine samples from healthy subjects or patients with urinary tract infections. Intra-genus cross-reactivity was observed only between L. pneumophila serogroups 2, 3, and 6. The Legionella reverse passive agglutination method was also evaluated with reference to reagent concentrations, test conditions, and subjectivity of reading test results. The method is rapid and does not require special equipment.     

Assessment of immunoglobulin-M immunosorbent agglutination assay (ISAGA) for detecting toxoplasma specific IgM.

An immunoglobulin-M immunosorbent agglutination assay (ISAGA) was introduced to detect toxoplasma specific IgM. This assay incorporates mu chain capture and use of entire toxoplasma trophozoites as an antigen source. The performance of the ISAGA was compared with that of a double sandwich enzyme linked immunosorbent assay (DS-ELISA) currently used in the Public Health Laboratory Service Toxoplasma Reference Laboratories. The ISAGA was found to be more sensitive than DS-ELISA but there was no demonstrable difference in the specificity or reproducibility between the two assays. The ISAGA is suitable for the diagnosis of acute toxoplasmosis in immunocompetent patients and as a screening test for recent infection in pregnant women. The persistence of ISAGA reactivity, however, is such that additional serological assessment is required to define the risk of congenital infection.     

Detection ofSalmonella species in faeces by latex agglutination in enrichment broth

A test was developed for the detection ofSalmonella spp. in stool enrichment broths using latex particles coated with polyvalent salmonella H antiserum. The test detected salmonella in 146 of 168 positive specimens and gave a positive result in two of 308 culture negative specimens. There was a positive predictive value of 99.6% and a negative predictive value of 95.4%, with an overall efficiency of 95%. Results were available within 18h of receipt compared to the 48–72h required for conventional methods. A positive result was also available within 4h for 17 of 18 specimens tested from patients with active salmonella gastroenteritis. The latex test was rapid, easy to perform and cost-effective, and would appear to be a useful aid in the rapid diagnosis of salmonella infection and carriage.     

Detection of white spot syndrome virus (WSSV) from hemolymph of Penaeid shrimps Penaeus japonicus by reverse passive latex agglutination assay using high-density latex particles

A simple reverse passive latex agglutination (RPLA) method for detecting white spot syndrome virus (WSSV) in the hemolymph of infected Kuruma shrimp (Penaeus japonicus) was developed. It was confirmed that WSSV could be detected from the shrimp hemolymph when the latex particles blocked with a casein protein were used as detection reagent. It became clear from the result of the infection trial that viruses are detectable by RPLA before the appearance of overt symptoms of this disease. In addition, an amplification product of 982 bp (s) derived from WSSV by PCR was detected in all the samples in which WSSV was detected by RPLA. This newly developed RPLA assay can examine many samples in a simple manner since hemolymph can be extracted more easily than any other organs. This assay can be used conveniently for virus detection in the culture pond of shrimps or in the field.     

Reversed passive latex agglutination assay for detection of toxigenic Corynebacterium diphtheriae.

A reversed passive latex agglutination (RPLA) assay for determining the toxigenicity of Corynebacterium diphtheriae is presented. Rabbit antitoxin antiserum was raised by using commercially available diphtheria toxoid. This antiserum reacted with the diphtheria toxin when the culture supernatant was assayed by Western blotting, and it did not cross-react with other extracellular antigens. Affinity-purified antibodies for latex sensitization were obtained by using a Hi Trap N-hydroxysuccinimide-activated column. Demonstration of toxin in five of seven clinical isolates was in accordance with the PCR assay and the Vero cell cytotoxicity test. Culture of the bacteria for 6 h was sufficient for toxin production, and an additional 6 h was needed to observe latex agglutination. Therefore, diphtheria toxin can be detected in 12 h by this method. The lowest concentration of diphtheria toxin detectable by the RPLA assay was about 5 ng/ml. The RPLA assay can provide a convenient and reliable method for laboratories involved in the identification of toxinogenic corynebacteria.     

A reverse passive latex agglutination test for the diagnosis of systemic candidosis

A new reverse passive latex agglutination test for the detection of serum antigen in systemic Candida albicans infection is reported. 1700 sera were examined from 91 patients who had either proven or suspected systemic candidosis, 183 patients who were colonized and 636 patients with no evidence of candidal infection. Thirty of the systemically infected patients had lymphoproliferative disorders and the rest a variety of surgical or medical diseases with no underlying neutropenia. The latex particles were sensitised with an antiserum raised in rabbits against a pressate of Candida albicans. The degree of antigenaemia was proportional to the likelihood of invasive disease such that a diagnostic cut-off point of 1 in 8 produced a test for systemic candidosis with a sensitivity of 90% and specificity of 80.4% in patients with lymphoproliferative disorders. In the remaining medical and surgical patients a diagnostic cut-off point of 1 in 10 produced a test with a sensitivity of 96.7% and specificity of 98.8%. The patients with lymphoproliferative disorders tended to produce lower serum antigen levels. The sera were also assayed for antibody using latex particles sensitised with pressate.     

Detection of parainfluenza IgM antibody by hemadsorption immunosorbent technique

A hemadsorption immunosorbent technique (HIT) was developed for the detection of immunoglobulin M (IgM) to parainfluenza virus types 1, 2, and 3. Twenty-six (90%) of twenty-nine patients under 6 yr of age from whom parainfluenza virus was isolated showed parainfluenza IgM antibody in one or both of their paired sera, with titres ranging from 320 to 81,920. In about one third of the cases IgM antibody was demonstrated in the initial sera taken 1 to 3 days after the onset of illness. Heterotypic IgM antibody responses were observed in about 20% of the patients. The HIT test was more sensitive than the hemagglutination inhibition (HI) and complement fixation tests in detecting a seroresponse in the 29 virus-positive children. The results of studies in older patients with HI titre rises to parainfluenza virus suggested that reinfection probably induced IgM antibody in a proportion of cases. The HIT test proved to be specific for the IgM class of antibody and avoided false-positive results due to rheumatoid factor. It permits an early presumptive diagnosis in a proportion of patients with parainfluenza infection.