Detection of rotavirus in stool specimens with monoclonal and polyclonal antibody-based assay systems.

Accurate diagnosis of rotavirus is important in both clinical and research situations. A total of 100 stool specimens from children with diarrhea were tested for rotavirus by electron microscopy. These specimens were then coded and tested for rotavirus by four procedures: a monoclonal antibody-based enzyme immunoassay (EIA) (Pathfinder; Kallestad Laboratories, Inc., Austin, Tex.), two polyclonal antibody-based EIAs (Rotazyme II; Abbott Laboratories, North Chicago, Ill.; and an EIA performed with reagents from the National Institutes of Health, Bethesda, Md. [NIH reagent EIA]), and a latex agglutination (LA) assay (Rotalex; Medical Technology Corp., Somerset, N.J.). The sensitivity of the monoclonal antibody EIA (95%) was superior to those of the polyclonal antibody EIAs (73% for Rotazyme II and 57% for the NIH reagent EIA) and the LA assay (61%). The specificity of the LA assay (98%) was slightly better than those of the other systems (88 to 96%). The positive and negative predictive values of the monoclonal antibody EIA (93 and 96%, respectively) were better than those of Rotazyme II (82 and 80%, respectively), the LA assay (96 and 76%, respectively), and the NIH reagent EIA (93 and 74%, respectively). The visual readings of the monoclonal antibody EIA correlated better with the spectrophotometric optical density readings than did the visual readings of the polyclonal antibody EIAs; however, the agreement of both with electron microscopy results was poor when 1+ or plus-minus readings were observed. The monoclonal antibody EIA is more sensitive and predictive than other rotavirus detection systems and second only to the LA assay in specificity in detecting rotavirus in stool specimens.     

Evaluation of a latex test for rotavirus detection.

A latex agglutination (LA) test (Slidex Rota-Kit; bioMérieux, Marcy-l'Etoile, France) was a rapid, easily used method for detecting rotavirus (RV) in pediatric fecal specimens. With 45 RV-positive and 50 RV-negative diarrhea specimens, the sensitivity of the LA test was 82%, and the specificity was 100%. Six other specimens produced indeterminate results. The frequency of positive LA tests appeared to be proportional to the concentration of virions in the stool.     

Choice of reference assay for the detection of rotavirus in fecal specimens: electron microscopy versus enzyme immunoassay.

Two previously demonstrated sensitive and specific enzyme immunoassays (EIAs) for rotavirus, one using polyclonal and monoclonal antisera (TestPack Rotavirus [TPK]; Abbott Laboratories) and the other using only monoclonal anti-rotavirus antibodies (Rotaclone [RTC]; Cambridge BioScience Corporation), were evaluated as potential reference assays for rotavirus testing in comparison with direct negative-staining electron microscopy (EM), the current laboratory standard. Two hundred and seven stool samples collected consecutively during the winter of 1989 from children with acute diarrhea admitted to a ward for infants from 0 to 2 years of age were tested by the EIAs and by EM. TPK specimens were read visually; RTC results were read spectrophotometrically. Specimens with discordant EIA and EM results were further evaluated by a fluorescent focus assay. Specimens positive by EM and those negative by EM but positive by fluorescent focus assay were considered to be positive for rotavirus. Of the 207 stools tested, 35 (17%) were positive for rotavirus by these criteria. EM had a sensitivity of only 80%. Specificities were 100% for RTC and EM and 89% for TPK. These findings indicate that EM, although very specific, is relatively insensitive compared with a highly sensitive monoclonal antibody-based EIA. An EIA with high sensitivity and specificity, such as RTC, is a more appropriate reference standard for rotavirus testing.     

Comparison of two commercially available enzyme immunoassays for detection of Clostridium difficile in stool specimens.

Clostridium difficile is the cause of most cases of pseudomembranous colitis, the most severe form of antibiotic-associated diarrhea. Rapid diagnosis guides both the treatment and the control of nosocomial spread of infection. Two enzyme immunoassay (EIA) kits developed for the rapid detection of C. difficile toxin A in fecal specimens, Premier (Meridian Diagnostics, Cincinnati, Ohio) and Tox-A test (TechLab, Virginia Polytechnic Institute Research Park, Blacksburg), were evaluated by using 410 fecal specimens. Seventy-six specimens were positive for C. difficile toxin B by the cytotoxin assay (prevalence rate, 19%). The Meridian EIA was positive for 71 of the 76 samples, yielding a sensitivity of 93%. The TechLab EIA detected 75 of the 76 positive samples, yielding a sensitivity of 99%. The Meridian and TechLab EIAs had specificities of 100 and 93%, respectively. These data indicate that both EIAs are suitable alternatives to the cytotoxin assay in routine diagnostic laboratories. However, confirmation of TechLab EIA-positive test results by the cytotoxin assay remains necessary.     

Evaluation of new commercial enzyme immunoassay for rotavirus detection.

We evaluated a new commercial enzyme immunoassay (EIA) for rotavirus (Rotavirus EIA; International Diagnostic Laboratories, Chesterfield, Mo.). A total of 161 consecutive stool samples (including 18 from infants less than 30 days old) submitted to the diagnostic laboratory at Children's Hospital, Washington University Medical Center, St. Louis, Mo., for rotavirus detection were tested by Rotavirus EIA and by Rotazyme II (Abbott Laboratories, North Chicago, III.) according to the instructions of the manufacturer. In addition, 16 samples from infants less than 30 days old without diarrhea were tested by both assays. Samples showing discrepant results after repeat testing were examined by electron microscopy. Nine samples yielding discrepant results were also tested by using a reference EIA directly on the specimen and on culture supernatants from two passages in MA 104 cells. Rotavirus EIA and Rotazyme II yielded concordant results for 85% of the samples. All of the 26 discrepant samples tested negative by Rotavirus EIA and positive (15 samples) or equivocal (11 samples) by Rotazyme II. These samples included 11 from symptomatic infants more than 30 days old, 2 from symptomatic infants less than 30 days old (neonates), and 2 from neonates without diarrhea. Rotavirus was not detected in any of the 24 that were examined by electron microscopy or in any of the 9 that were tested by the reference EIA. The sensitivity, specificity, positive predictive value, and negative predictive value were 100% for Rotazyme EIA and 100, 90, 70, and 100%, respectively, for Rotazyme II. Rotavirus EIA was comparable to Rotazyme II in ease of performance. We conclude that Rotavirus EIA is equally sensitive and more specific than Rotazyme II for detecting rotavirus. Rotavirus EIA is a practical and accurate rotavirus assay for use in clinical laboratories.     

Comparison of a dot immunobinding assay, latex agglutination, and cytotoxin assay for laboratory diagnosis of Clostridium difficile-associated diarrhea.

C. diff-CUBE, a dot immunobinding assay (DIA) (Difco Laboratories, Ann Arbor, Mich.) for detection of Clostridium difficile toxin A in stool specimens, was compared with latex agglutination (LA) (Marion Laboratories, Kansas City, Mo.) and cytotoxin assay (CTA) for the laboratory diagnosis of C. difficile-associated diarrhea. A total of 200 stool specimens collected from 169 patients with suspected C. difficile diarrhea were tested. Of the 198 specimens evaluated by all three methods, 36 (18%) from 36 patients were positive by one or more of the tests. Twenty-five, 26, and 23 specimens were positive by CTA, DIA, and LA, respectively; 14 were positive by all three methods. Eight specimens yielded nonspecific LA test results; all eight were negative by CTA, and one was positive by DIA. DIA results agreed with CTA results in 183 (92%) cases and with LA results in 175 (88%) cases. CTA and LA results agreed in 179 (90%) cases. Freezing of the specimen did not appear to adversely affect either the DIA or LA test. These preliminary results suggest that C. diff-CUBE may be useful as a rapid screen for the diagnosis of C. difficile-associated diarrhea. However, for optimum laboratory diagnosis, further testing of all stools that are negative by DIA is warranted.     

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.     

Comparison of six methods for the detection of antibody to cytomegalovirus.

Five commercial assays were compared to a standardized complement fixation (CF) test for the detection of antibody to cytomegalovirus. Two hundred and thirty serum specimens were analyzed. In addition, nine pairs of acute- and convalescent-phase sera were tested by two of the commercial assays. The assays were compared as to sensitivity, specificity, and positive and negative predictive value, as well as incidence of false-positive and -negative results. Samples which did not agree in all the assays were retested and tested with an indirect fluorescent-antibody assay. Of 228 specimens, 103 (45.2%) were positive by CF. Of the 230 samples, 2 (0.9%) were inconclusive by CF and readable in the other assays. Of the 230 specimens, 97 (42.2%) were positive by an enzyme immunoassay (EIA; Litton Bionetics), 100 (43.5%) were positive by a second EIA (Abbott Laboratories), 104 (45.2%) were positive by a third EIA (M. A. Bioproducts). One hundred and eight (47.0%) were positive by indirect hemagglutination (IHA; Cetus Corporation), and 110 (47.8%) were positive by latex agglutination (LA; Hynson, Westcott and Dunning). Sensitivity and specificity were similar with all the assays (93 to 100%). The greater numbers of positive results by IHA and LA were confirmed by repeat CF testing at less than 1:8 dilution, and by indirect fluorescent-antibody assay. Acute- and convalescent-phase serum pairs showed a significant rise in antibody titer when tested by anticomplement immunofluorescence, IHA, and LA. There was good agreement among the assays, with LA having the highest sensitivity.     

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.     

Discrepancies in viral gastroenteritis diagnosis: an unusual dual reovirus-adenovirus infection case.

BACKGROUND: A variable rate of false-positive results may be observed with commercial assays for the detection of rotavirus and adenovirus antigen in stool specimens, depending on the quality of the reagents and the presence of potentially interfering substances in stool samples. OBJECTIVE: The present report analyse the discrepant results that could be obtained by the commercially available diagnostic tests and that can mask the reliable viral diagnosis. STUDY DESIGN: One fecal sample was collected from a hospitalized child aged 6 months with acute watery diarrhea and dehydration. The fecal specimen was processed the same day for the rotavirus and adenovirus antigen detection. RESULTS: The sample was positive for rotavirus antigen by one-step membrane test based on immunochromatographic assays (ICA) and enzyme immunoassays (EIA) monoclonal test but it was negative by an EIA polyclonal test, polyacrylamide gel electrophoresis (PAGE) and RT-PCR assays. In the other hand, the sample was positive for adenovirus antigen by ICA and EIA adenovirus type 40/41. Finally, the sample showed by PAGE an electrophoretic profile resembled that of reovirus. CONCLUSION: The use of a wide repertory of diagnosis tests allowed to reach an unusual reovirus-adenovirus type 40/41 dual infection. This case also point out the potential participation of reovirus in the ethiology of the diarrhea illness.     

Identification of viral agents associated with diarrhea in young children during a winter season in Beijing, China.

BACKGROUND: Viral diarrhea remains a major cause of childhood morbidity and mortality worldwide. Although rotavirus was extensively studied in China, few comprehensive studies of all viral agents related to diarrhea in children have been conducted. OBJECTIVES: Our study was performed to investigate the role of enteric viruses in acute diarrhea in our country and to evaluate methods that could be used in routine diagnostics. STUDY DESIGN: One hundred stool samples were collected from children under 5 years of age seeking medical care for acute diarrhea during the winter season 2000/2001 in Beijing Children's Hospital. All specimens were initially screened microscopically for leucocytes/red blood cells. Samples with negative results were analyzed for virus presence using commercial EIAs and/or in-house RT-PCRs. RESULTS: At least one viral agent was found in 67% of the specimens. The frequency of rotavirus, astrovirus, norovirus and enteric adenovirus was 59%, 8%, 6% and 2%, respectively. Dual infections were found in 9.0% (6/67) of the positive samples. The results from rotavirus and astrovirus EIAs were concordant with those of rotavirus and astrovirus RT-PCRs. CONCLUSIONS: Enteric viruses play an important role in pediatric diarrhea during the winter season in China. A combination of microscopic examination of stool samples with specific EIA assays to detect virus antigen in stool specimens may be suitable for routine diagnostics.     

Large-Scale Evaluation of the Immuno-Mycologics Lateral Flow and Enzyme-Linked Immunoassays for Detection of Cryptococcal Antigen in Serum and Cerebrospinal Fluid

Cryptococcosis is a systemic infection caused by the pathogenic yeasts Cryptococcus neoformans and C. gattii. Detection of cryptococcal capsular antigen (CrAg) in serum and cerebrospinal fluid (CSF) plays an important diagnostic role. We prospectively compared the new Immuno-Mycologics Inc. (IMMY) lateral flow assay (LFA) and enzyme immunoassay (EIA) to our current CrAg test (Premier EIA; Meridian Bioscience Inc.). Discordant samples were retested with the latex-Cryptococcus antigen test (IMMY) and using serotype-specific monoclonal antibodies (MAbs). A total of 589 serum and 411 CSF specimens were tested in parallel. Qualitative agreement across assays was 97.7%. In all, 56 (41 serum and 15 CSF) samples were positive and 921 (527 serum and 394 CSF) samples were negative by all three assays. The 23 discrepant specimens were all Meridian EIA negative. Of 23 discordant specimens, 20 (87.0%) were positive by both the IMMY LFA and EIA, 2 were LFA positive only, and 1 was EIA positive only. Eleven discrepant specimens had adequate volume for latex agglutination (LA) testing; 8 were LA positive, and 3 were LA negative. LA-negative samples (2 CSF samples and 1 serum) had low IMMY LFA/EIA titers (≤1:10). Serotype-specific MAb analysis of the LA-positive samples suggested that these specimens contained CrAg epitopes similar to those of serotype C strains. In conclusion, the IMMY assays showed excellent overall concordance with the Meridian EIA. Assay performance differences were related to issues of analytic sensitivity and possible serotype bias. Incomplete access to patient-level data combined with low specimen volumes limited our ability to fully resolve discrepant results.     

Comparison of commercial latex agglutination and sandwich enzyme immunoassays with a competitive binding inhibition enzyme immunoassay for detection of antigenemia and antigenuria in a rabbit model of invasive aspergillosis

A commercial latex agglutination assay (LA) and a sandwich enzyme immunoassay (SEIA) (Sanofi Diagnostics Pasteur, Marnes-la-Coquette, France) were compared with a competitive binding inhibition assay (enzyme immunoassay [EIA]) to determine the potential uses and limitations of these antigen detection tests for the sensitive, specific, and rapid diagnosis of invasive aspergillosis (IA). Toward this end, well-characterized serum and urine specimens were obtained by using a rabbit model of IA. Serially collected serum or urine specimens were obtained daily from control rabbits or from rabbits immunosuppressed and infected systemically with Aspergillus fumigatus. By 4 days after infection, EIA, LA, and SEIA detected antigen in the sera of 93, 93, and 100% of A. fumigatus-infected rabbits, respectively, whereas antigen was detected in the urine of 93, 100, and 100% of the rabbits, respectively. False-positive results for non-A. fumigatus-infected rabbits for EIA, LA, and SEIA were as follows: for serum, 14, 11, and 23%, respectively; for urine, 14, 84, and 90%, respectively. Therefore, although the sensitivities of all three tests were similar, the specificity was generally greater for EIA than for LA or SEIA. Infection was also detected earlier by EIA, by which the serum of 53% of A. fumigatus-infected rabbits was positive as early as 1 day after infection, whereas the serum of only 27% of the rabbits tested by LA was positive. Although the serum of 92% of A. fumigatus-infected rabbits was positive by SEIA as early as 1 day after infection, the serum of a high percentage (50%) was false positive before infection. The urine of 21% of A. fumigatus-infected rabbits was positive by EIA as early as 1 day after infection, and the urine of none of the rabbits was false positive before infection. When EIA results for urine specimens were combined with those for serum, sensitivity was improved (i.e., 67% of rabbits were positive by 1 day after infection and only one rabbit gave a false-positive result). A total of 93% of A. fumigatus-infected rabbits were positive for antigen in urine as early as 1 day after infection and the urine of 100% of the rabbits was positive by SEIA. However, before infection, 79% of A. fumigatus-infected rabbits were false positive for antigen in urine by LA and 90% were false positive for antigen in urine by SEIA. These data indicate that the EIA has the potential to be used to diagnose IA with both serum and urine specimens and to detect a greater number of infections earlier with greater specificity than the specificities achieved with the commercial tests.     

Use of aminotransferase, hepatitis C antibody, and hepatitis C polymerase chain reaction RNA assays to establish the diagnosis of hepatitis C virus infection in a diagnostic virology laboratory.

Clinical and therapeutic decisions for hepatitis C virus (HCV) infection depend on factors that include documentation of past infection as well as identification of those who might benefit from antiviral chemotherapy with systemic interferon. To evaluate the ability of a diagnostic laboratory to accurately identify such patients, we compared results obtained with serum transaminase assays, two HCV antibody assays (enzyme immunoassay [EIA] and immunoblot), and a polymerase chain reaction (PCR)-based assay for HCV RNA using a group of consecutively submitted samples within our university-based diagnostic virology laboratory and sera from a population of random blood donors. One hundred percent of specimens with R values of greater than 3.0 in the HCV EIA were positive in the confirmatory immunoblot. However, 25% of specimens with EIA R values of between 1.0 and 3.0 were not confirmed by either recombinant immunoblot assay (RIBA) or RNA PCR assay (false-positive specimens). A significant correlation (P less than 0.01) between increasing reactivity in the RIBA and positivity in the RNA PCR assay was found. The incidence of HCV viremia, as determined by the RNA PCR assay, was 73% for confirmed seropositive specimens, 33% for seropositive specimens with indeterminate RIBA results, 12% for seronegative specimens obtained from infected patients, and 2.0% for seronegative specimens obtained from uninfected blood donors. In contrast, serum transaminase testing did not correlate with the RNA PCR assay for HCV. Use of the EIA and immunoblot assay followed by RNA PCR testing will identify most patients who are viremic with HCV.     

Strategies for reliable diagnosis of hepatitis C infection: the need for a serological confirmatory assay.

The aim of the study was to examine whether the diagnosis of Hepatitis C (HCV) infection can be obtained reliably without using an immunoblot-based confirmation assay. 1,708 EIA-reactive serum samples were examined retrospectively for (i) optical density value in the screening assay, (ii) reactivity in an immunoblot assay, and (iii) result by RT PCR. In 1,394 (81.0%) samples positive results were obtained by both the HCV EIA and the confirmation assay. OD-values > or = 2.2 were observed in 1026 of these samples, but covered the range from 0.4 to 2.1 in the other 368 samples. The combination of HCV EIA reactivity and indeterminate immunoblot assay was observed in 134 (7.8%) serum samples. HCV RNA was detected in 58 cases by PCR. The OD-values of these 58 samples ranged from 0.4 to >2.2. Especially reactivity against the core recombinant protein was indicative of PCR positivity. The reactivity by the HCV EIA could not be confirmed by immunoblot assay or PCR in 180 (10.5%) sera. These false reactive sera showed OD values by EIA from 0.3 to 2.1. It is concluded that no threshold values can be defined which would allow differentiation between positive, indeterminate, and false reactive result by HCV EIA without producing an unacceptably high number of false negative diagnoses. Not using immunoblot-based confirmation would result in many additional PCR examinations. Therefore, confirmation of reactive HCV EIA results by a serological confirmatory assay must remain an essential part of the diagnostic procedure.     

Development of a rapid enzyme immunoassay for Clostridium difficile toxin A and its use in the diagnosis of C. difficile-associated disease.

A rapid (2.5 h) direct enzyme immunoassay (EIA) for Clostridium difficile toxin A was developed for clinical use. Specimen centrifugation and filtration were not required. The EIA detected toxin A levels in patient stool as low as 20 pg (2 ng/ml of stool). The test was 5,000 times more sensitive for toxin A than it was for toxin B and did not react with a panel of other bacterial species with the exception of one highly toxigenic strain of Clostridium sordellii. The EIA was compared with the cytotoxin assay, culture of toxigenic C. difficile (toxigenic culture), and latex agglutination by using 313 fresh stool specimens submitted from patients with suspected C. difficile-associated disease. Results read visually and with a plate reader were similar. Sixty-two specimens were positive by one or more tests, but only 22 (35%) were positive by all four laboratory methods. The EIA was 84.1% sensitive and 98.9% specific when it was compared with the cytotoxin assay. The use of toxigenic culture to referee discrepant results (EIA versus cytotoxin assay) showed the EIA sensitivity and specificity to be 95.1 and 99.3%, respectively, with respect to other laboratory methods. Patient charts were reviewed for antibiotic-associated diarrhea on 108 specimens, including all those that were positive by at least one test method. Of 34 patients determined to have C. difficile-associated disease, 29 (85.3%) were positive by EIA, 32 (94.1%) were positive by the cytotoxin assay, 27 (79.4%) were positive by toxigenic culture, and 20 (58.8%) were positive by latex agglutination. Seven patients with antibiotic-associated diarrhea had a positive latex result, but results were negative by EIA, the cytotoxin assay, and toxigenic culture. The EIA demonstrated high specificity and good sensitivity for C. difficile-associated disease cases. The test can be used alone or in combination with the cytotoxin assay or toxigenic culture to provide rapid and sensitive results.     

Comparison of the PREMIER cryptococcal antigen enzyme immunoassay and the latex agglutination assay for detection of cryptococcal antigens.

A new enzyme immunoassay (EIA), PREMIER Cryptococcal Antigen, was compared with latex agglutination (LA) for the detection and quantitation of circulating capsular polysaccharide antigen from Cryptococcus neoformans. The clinical evaluation of PREMIER EIA as a screening assay, including 475 specimens with 120 LA and EIA positives, resulted in 99% sensitivity and 97% specificity. The clinical specimens included sera and cerebrospinal fluids as well as 10 rheumatoid factor-positive and 20 anti-nuclear antibody-positive serum samples. This monoclonal antibody-based assay detects serotypes A to D at 0.63, 0.63, 7.8, and 62 ng/ml, respectively. With three different known positive specimens, the assay was found to yield coefficients of variation of 2 to 12% for intra- and interassay comparisons of precision and reproducibility. The primary use for semiquantitative values derived with the LA or EIA is to follow the course of disease and monitor drug therapies. The present data suggest that the PREMIER EIA will be a valuable method for this purpose. We conclude that the PREMIER Cryptococcal Antigen EIA provides a rapid, convenient, and reliable antigen detection method for screening and semiquantitative determination of antigen levels.     

Prevalence of group C rotavirus among children in Rhode Island, United States.

BACKGROUND: Group C rotavirus causes sporadic cases and outbreaks of acute diarrhea in humans but its burden as a cause of severe gastroenteritis in children remains unclear. OBJECTIVES: To investigate the epidemiology and burden of group C rotavirus gastroenteritis among children in Rhode Island, United States. STUDY DESIGN: Diarrhea stool specimens from 124 children < or =10 years of age were collected, screened for group C and A rotavirus by EIA specific for each group, and further examined by nested PCR and Southern hybridization using primers and probes specific to the VP7 gene of human group C rotavirus. Group C rotavirus-positive fecal specimens were also examined by EM. RESULTS: Rotavirus was detected in 73 (59.0%) of 124 fecal samples. These included 53 (42.7%) positive for group A, 5 (4.0%) for group C and 15 (12.1%) for both group A and C rotaviruses. Examination of group C-positive samples by EM revealed the presence of largely empty or damaged rotavirus-like particles. CONCLUSION: These findings indicate that group C rotavirus is an important cause or a contributing cause of diarrhea among infants and older children in Rhode Island, United States.     

Latex agglutination test for rubella antibodies: report based on data from the College of American Pathologists surveys, 1983 to 1985

In the College of American Pathologists (CAP) rubella survey program, 45% of laboratories rely on the latex agglutination (LA) card assay for detecting rubella immunoglobulin G (IgG) antibodies. By using CAP survey data over a 3-year period, we compared LA results with hemagglutination inhibition (HI) and enzyme immunoassay (EIA) results. EIA indices were used to classify results into three categories: nonimmune, EIA index of 0.300 or less; borderline, EIA index of 0.300 to 0.619; and immune, EIA index of 1.700 or greater. There was 91% or more agreement between LA, HI, and EIA for categories i and iii. In category ii, the response from LA users varied, depending on the level of antibody present in the survey samples; at an EIA index of 0.346, 81% reported nonimmune status, whereas at an EIA index of 0.619, 48% reported nonimmune status. Less than 10% indicated borderline status. In testing of samples in the same category, approximately 40%, using the HI method, reported titers of less than 1:8 (nonimmune status). Among EIA users, 97 to 99% regarded the specimens as nonimmune. On analysis of specimens in the borderline category, the LA test showed a pattern of sensitivity and specificity comparable to that reported with the HI technique, whereas the EIA method showed a greater degree of precision. The LA card assay provides a rapid screening test in which LA is read macroscopically, and the procedure differs considerably from the fully quantitative HI and EIA methods.(ABSTRACT TRUNCATED AT 250 WORDS)