The group A rotavirus staphylococcal co-agglutination test was evaluated and its sensitivity and specificity compared with an in-house enzyme-linked immunosorbent assay (ELISA) and a commercial latex agglutination test (Rotalex). In addition, the storage stability of the staphylococcal reagents was ascertained. Examination of 136 clarified suspensions of diarrhoeal faeces by the staphylococcal co-agglutination test revealed a high proportion of false positives (26%) and uninterpretable results (34%) due to non-specific agglutination. Non-specific agglutination could be removed effectively by prior absorption of the clarified faecal specimens with unsensitized staphylococci. The staphylococcal co-agglutination test was less sensitive and specific than the in-house enzyme-linked immunosorbent assay but was comparable to the Rotalex slide latex agglutination test. The staphylococcal reagents have a shelf life of at least 29 weeks.
The usefulness of counterimmunoelectrophoresis (CIEP) and coagglutination (COAG) methods in the diagnosis of bacterial meningitis was evaluated. Out of the 31 cerebrospinal fluid (CSF) specimens which had a cell count of >5 x10^6 wbc/l and were negative on gram stain and culture, pneumococcal antigens were detected in four specimens and Haemophilus influenzae type b antigen was detected in one specimen by both the methods. No false positives were detected in 10 specimens obtained from cases of febrile fits whose CSF showed no evidence of meningitis. One CSF sample, from which Klebsiella spp. was isolated, cross reacted with the meningococcal polyvalent group A-D antiserum in the CIEP test. From this study we found that these methods are rapid, simple and useful adjunctive tests In the diagnosis of bacterial meningitis, especially in the partially treated cases.
The purpose of this investigation was to evaluate the usefulness of a co-agglutination procedure for the typing of Flavobacterium meningosepticum. The sensitivity and specificity of the co-agglutination test was compared to the slide agglutination test using reference strains of the bacterial species. Antisera were characterized by both technics to determine their titer and working dilution. The specificity of the sera was assessed by performing tests which include strains of other species and serotypes. A collection of 47 strains of F. meningosepticum isolated from clinical specimens were typed by both co-agglutination and slide agglutination methods. Co-agglutination proved to be markedly more specific than the slide procedure although both methods were similar in sensitivity. It was concluded that co-agglutination proved to be an excellent method for the serotyping of F. meningosepticum.
The Serodia-HCV Particle Agglutination (HCV-PA) for the detection of HCV antibodies was compared with the Enzyme Immunoassay Test (UBI HCV EIA) for possible in-house use. A total of 150 specimens were analysed using UBI HCV EIA and Serodia-HCV PA. Of these, 80 (53.3%) were both PA and EIA positive and 59 (39.3%) were negative by both techniques. Eleven sera (7.4%) were found to be EIA-positive but PA-negative. These 11 discordant sera were further tested by the LiaTek-HCV III Immunoassay (Organon Teknika). Ten were found to be line immunoassay negative and one was line immunoassay positive. Failure of the PA to detect the HCV positive serum meant that a small proportion of HCV antibody positives may be missed by the PA test. We conclude that (i) EIA should continue to be the first line screening test in our laboratory, (ii) PA with its 100% specificity could be a useful supplementary screen for all EIA-positive sera and finally (iii) line immunoassay could be used on sera to resolve discordant results in the EIA and PA assays.