A rapid, point-of-care red blood cell agglutination assay detecting antibodies against SARS-CoV-2.

The COVID-19 pandemic has caused significant morbidity and mortality. There is an urgent need for serological tests to detect antibodies against SARS-CoV-2, which could be used to assess past infection, evaluate responses to vaccines in development, and determine individuals who may be protected from future infection. Current serological tests developed for SARS-CoV-2 rely on traditional technologies such as enzyme-linked immunosorbent assays (ELISA) and lateral flow assays, which have not scaled to meet the demand of hundreds of millions of antibody tests so far. Herein, we present an alternative method of antibody testing that depends on one protein reagent being added to patient serum/plasma or whole blood with direct, visual readout. Two novel fusion proteins, RBD-2E8 and B6-CH1-RBD, were designed to bind red blood cells (RBCs) via a single-chain variable fragment (scFv), thereby displaying the receptor-binding domain (RBD) of SARS-CoV-2 spike protein on the surface of RBCs. Mixing mammalian-derived RBD-2E8 and B6-CH1-RBD with convalescent COVID-19 patient serum and RBCs led to visible hemagglutination, indicating the presence of antibodies against SARS-CoV-2 RBD. B6-CH1-RBD made in bacteria was not as effective in inducing agglutination, indicating better recognition of RBD epitopes from mammalian cells. Given that our hemagglutination test uses methods routinely used in hospital clinical labs across the world for blood typing, we anticipate the test can be rapidly deployed at minimal cost. We anticipate our hemagglutination assay may find extensive use in low-resource settings for detecting SARS-CoV-2 antibodies.

Cost-effectiveness of detection of intestinal amebiasis by using serology and specific-amebic-antigen assays among persons with or without human immunodeficiency virus infection.

Among 345 persons who underwent indirect hemagglutination (IHA) serological assays and assays of specific amebic antigens in their stool samples, 24 of 36 (66.7%) who were seropositive for Entamoeba histolytica had intestinal amebiasis as determined by antigen assays compared with 2 of 309 (0.2%) who were seronegative (odds ratio, 307; 95% confidence interval, 64.9 to 1,451). The estimated cost to detect a case of intestinal amebiasis by serology followed by antigen assays ($52) could be reduced by 74.3% and 69.9%, respectively, compared with the costs of the concurrent use of both assays ($202) and the antigen assays alone ($173). Our finding suggests that IHA assays followed by specific-amebic-antigen assays can be cost-effective in the diagnosis of intestinal amebiasis among persons with or without human immunodeficiency virus infection who are at risk for E. histolytica infection.

A cost-effective particle agglutination assay to detect viral antibodies in dried blood spots--a simple solution to HIV and HCV screening.

OBJECTIVES: To conduct a serological survey of human immunodeficiency virus (HIV) and hepatitis C virus (HCV) in Gabon and Ga-Rankuwa, South Africa. A secondary objective was to test a novel, simple, inexpensive agglutination assay for anti-HIV IgG and anti-HCV IgG from blood samples stored as spots dried onto filter paper. DESIGN: Blood from heel pricks was dried onto filter paper and stored. Blood was eluted from the spots and serum antibody was then assayed using a modified agglutination assay--blood was added to gelatin agglutination beads that had been sensitised with viral antigen. A positive result showed as an agglutination pattern while a negative result appeared as a tight bead. SUBJECT: This was a hospital-based study involving 271 neonates at Ga-Rankuwa Hospital, South Africa, and 856 patients ranging in age from three months to over 50 years who attended clinics in Gabon. RESULTS: Seroprevalence to HIV was determined in Ga-Rankuwa to be just under 14% (13.8%). Antibodies to HCV were not detected. In Gabon, the prevalence to HIV was just under 1% (0.82%) with a relatively high incidence of HCV, nearing 4% (3.79%). CONCLUSION: The sensitivity of the agglutination assay compared favourably to enzyme immune assay (EIA) with respect to sensitivity, simplicity and cost. This assay may be useful in sero-epidemilogical assays in developing countries.

Evaluation of 2-column agglutination versus conventional tube technique for antibody screening.

The study aimed to determine the specificity and sensitivity of the Ortho BioVue two-column agglutination system for the detection of low concentrations of clinically significant antibodies in serum. The BioVue system was compared with the conventional tube technique (LISS-Coombs indirect antiglobulin test), and the two-stage Papenzyme test was used to resolve discrepancies between the two methods. We tested 3000 serum samples from randomly selected patients at King Hussein Medical Centre. Both the antibody screening and identification gave negative results in 2952 patients and positive results in 48 patients. We found the BioVue system to be the more sensitive technique. However, if papain enzyme-treated cells were included in the conventional tube technique when applied to antibody screening and identification, both methods would be of comparable sensitivity.

Choice of fecal occult blood tests for colorectal cancer screening: recommendations based on performance characteristics in population studies: a WHO (World Health Organization) and OMED (World Organization for Digestive Endoscopy) report.

OBJECTIVE: There is now strong evidence that screening for colorectal cancer with fecal occult blood tests (FOBTs) is effective in reducing the incidence and mortality of this disease. Various FOBTs are now available with a wide range of evidence supporting their use. The purpose of this study was to review published data on the performance of these FOBTs to provide recommendations for their effective use in screening. METHODS: A joint committee representing the World Health Organization and the World Organization for Digestive Endoscopy was established for this study. A process was designed that would search the literature systematically for evidence of FOBT performance. Criteria for including studies in this paper were established based on study design, cohort size, and performance variables reported. RESULTS: Of the guaiac tests, Hemoccult SENSA had the highest sensitivity for cancer and adenomas but a high test positivity. It had a better readability than the older Hemoccult II test. Immunochemical tests, HemeSelect, FlexSure OBT, and Immudia Hem Sp have acceptable performance characteristics and are easier for participants to use but are more expensive. These tests have been well studied in large cohorts, but only Immudia Hem Sp is commercially available. CONCLUSIONS: At present, there is no extensively studied FOBT that fulfills the needs for all target populations worldwide. Choice of FOBT should take into account population dietary compliance and colonoscopy resources: The more sensitive newer tests should be used if dietary compliance is good (in the case of guaiac tests) and colonoscopy resources are adequate for diagnostic workup of people who test positive. Immunochemical tests remove the difficulties created by diet and drug restrictions and are more amenable to standardized development and quality control.

Evaluation of a rapid enzyme immunoassay for diagnosis of hepatic amoebiasis.

We compared the capability of rapid enzyme immunoassay (EIA) to detect antiamoebic antibodies during hepatic amoebiasis with those of indirect hemagglutination and latex agglutination. EIA is simple to perform and rapid (20 min) and does not require any special equipment (optical reading is sufficient). EIA of 143 sera (including 43 from patients with proven hepatic amoebic abscess, 33 from patients with other hepatic disorders and/or parasitic infections, and 67 from healthy individuals) yielded a specificity, a sensitivity, and positive and negative predictive values of 100, 93, 100, and 97.1, respectively. This test could thus be considered another valuable tool for the diagnosis of hepatic amoebiasis.

Unreliability of current screening tests for syphilis in chronic psychiatric patients.

OBJECTIVE: This study examined whether psychiatrists perform adequate diagnostic screening for syphilis in patients with chronic mental illness. METHOD: Two hundred patients with chronic mental illness underwent testing for syphilis with the commonly used RPR test and the microhemagglutination assay for Treponema pallidum (MHA-TP). Sensitivities of the two tests were compared. RESULTS: A substantial number of patients with negative results on RPR tests had reactive MHA-TPs and would have not been identified as having had syphilis with the use of RPR testing alone. CONCLUSIONS: Nontreponemal tests such as the RPR test are less likely than treponemal tests to detect syphilis appropriately in chronically mentally ill patients, and specific treponemal tests such as the MHA-TP should be considered.

Evaluation of nine serological tests for diagnosis of Lyme borreliosis.

Two hundred serum specimens including 13 sera from patients with early Lyme borreliosis, 21 patients with late Lyme borreliosis, 15 rheumatoid factor positive sera, 31 sera from patients with syphilis and 84 sera from healthy controls were used to evaluate the following assays for the detection of antibodies to Borrelia burgdorferi: two in-house enzyme immunoassays (EIAs), two in-house immunofluorescent antibody assays (IFAs), a commercial haemagglutination assay (HA) (Diagast) and four commercial EIAs (Diagast, Dako, Diamedix, Whittaker Bioproducts). In early and late Lyme borreliosis sera sensitivity ranged from 8% to 62% and from 62% to 86% respectively. With the exception of the Dako EIA, which was signifcantly more sensitive in early Lyme borreliosis (62%) than the Diagast HA (8%) (p = 0.05), differences in sensitivity were not significant. In healthy controls the specificity was > or = 95% for all tests. Taking into account sensitivity, specificity, intra-test and inter-test precision, ease of performance and cost, the Dako EIA and Diamedix EIA were shown to be good alternatives to the in-house EIA and in-house IFA. Because of its low sensitivity in diagnosis of both early and late Lyme borreliosis, use of the Diagast HA should be discouraged.

A cost-effectiveness analysis of a simple micromethod for hepatitis B screening in hepatitis B virus control programmes.

We developed a simple micromethod for identifying mothers who are most likely to transmit hepatitis B infection to their infants, using reverse passive haemagglutination for detecting HBsAg (hepatitis B surface antigen) in capillary blood. This screening method was evaluated against other strategies for hepatitis B control by means of decision- and cost-effectiveness analyses. The micromethod was shown to be cost-effective when the cost of hepatitis B vaccine was high. However, with increasingly reduced costs of the vaccine, it may have a limited role in a programme of mass immunization for hepatitis B.

Hemagglutination treponemal test for syphilis.

Sera from 290 hospital patients were tested to compare the sensitivity, specificity, and reproducibility of the hemagglutination treponemal test for syphilis (HATTS) with the fluorescent treponemal antibody absorption test (FTA-ABS). Complete agreement was obtained between the methods when 142 syphilitic sera from patients with various stages of syphilis were tested. By using clinical histories, the specificity with 148 nonsyphilitic sera was determined to be 100% for the HATTS and 96.6% (143 of 148) for the FTA-ABS. Satisfactory reproducibility was obtained with both methods. Compared with the FTA-ABS, the HATTS was more specific, easier, and more economical to perform. We therefore recommend the HATTS as a suitable alternative to the FTA-ABS.

Evaluation and comparison of two assays for detection of immunity to rubella infection.

Two commercially available rapid screening tests, Rubacell (Abbott Laboratories; passive hemagglutination) and FIAX (International Diagnostic Technology; indirect immunofluorescence) were compared with a standard hemagglutination inhibition assay for detection of immunity to rubella infection. In tests of approximately 300 sera, both rapid assays were specific and sensitive and showed a high predictive value of a positive result. Within-run reproducibility studies were excellent for both tests; however, Rubacell was superior to FIAX with respect to time-cost analysis.