A rotavirus staphylococcal co-agglutination test

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.

Rapid diagnosis of cholera by coagglutination test using 4-h fecal enrichment cultures

A simple, rapid, and reliable method to detect Vibrio cholerae in fecal specimens would assist in the management of cases of severe diarrhea, especially since most such cases occur in areas with minimal laboratory facilities. A coagglutination test was used to detect V. cholerae antigen in bile-peptone broth incubated with feces. In the technique, Staphylococcus aureus Cowan 1 coated with anti-V. cholerae O1 antiserum was tested with cultures incubated for 4 h. When 165 specimens were tested, the sensitivity, specificity, and accuracy of the test, compared with standard culture methods, were 97, 99, and 98%, respectively. These promising results were better than those of dark-field microscopy using the same specimens, and the test was logistically easy to perform. The coagglutination test using enrichment broth culture of feces is a simple and rapid method which may be used to confirm a diagnosis of cholera.

A new screening test for rotavirus infection

A simple and rapid staphylococcal coagglutination test, using rabbit antisera prepared against Nebraska calf diarrhea virus (NCDV), is described for the detection of rotavirus in neonatal fecal specimens. When the samples were examined directly using the coagglutination test, more than 60% of the specimens agglutinated the control reagent. These non-specific reactions were markedly reduced by preincubation of the specimens with non-immune rabbit serum and further heating at 80 degrees C for 45 min. Such treatment did not reduce the specific activity in the coagglutination test when rotavirus-containing stools were tested. The coagglutination test was compared with ELISA in 290 stools positive or negative for rotavirus. The sensitivity of the coagglutination test was 92%, the specificity 91% and the predictive value 31%. These results indicate that coagglutination is a suitable test for rapid screening of rotavirus infection in clinical practice.

Latex immunoassay for rapid detection of rotavirus

A latex agglutination (LA) test was evaluated for the detection of human rotaviruses in stool specimens. Both antiserum and immunoglobulin G (IgG)-sensitized latex particles were used, with IgG-coated beads being more sensitive for human rotavirus antigen detection. Latex beads sensitized with anti-simian-SA-11 IgG were stable for at least 8 months when stored at 4 degrees C. The sensitivity of the test was compared with that of the Rotazyme (Abbott Laboratories, Diagnostics Div., North Chicago, Ill.) test. The least number of particles detected was 9.0 X 10(5) particles by the LA test versus 4.5 X 10(5) particles by the Rotazyme test. When 10 stool specimens were serially diluted for antigen endpoint determinations, the geometric mean titer by the LA test was 592 versus 1,280 by the Rotazyme test. Forty-three stool samples positive by the Rotazyme test were all positive by the LA test, and no false negative results were detected. Unconfirmed false positive reactions ranged between 8 and 24%. The LA test for rotavirus antigen detection is direct, easy to perform, sensitive, quick, and may have application for use in diagnostic laboratories, emergency rooms, and physician's offices.