Concordance of four commercial enzyme immunoassay and three immunoblot formats for the detection of Lyme borreliosis antibodies in human serum: the two-tier approach remains.

Serological tests show considerable variation in their ability to correctly diagnose Lyme borreliosis (LB). This study compared four commercially available screening enzyme immunoassays (EIA) for the detection of LB IgG using either whole cell lysate (WCL) antigens, purified proteins or recombinant antigens with the second-tier whole cell sonicate (WCS) western immunoblots or recombinant antigen line blots. A consensus between three EIA results from 222 patient sera was designated as a point of comparison for each method which gave 66 positive and 156 negative results. The positive predictive values (PPV) of WCL EIA were 40% for the MarDx Diagnostics Borrelia burgdorferi EIA 'combined' IgG and IgM (Trinity Biotech) and 55% for the EUROIMMUN plus VlsE IgG. These were significantly lower PPVs than that produced by the recombinant antigen-based EIA NovaLisa Borrelia burgdorferi IgG-ELISA (NovaTec Immunodiagnostica) and the EUROIMMUN Anti-Borrelia Select ELISA IgG (90% and 100%, respectively; p = 0.02). The WCS western immunoblot using B. burgdorferi and B. afzelii separately showed a high PPV of 91% but its positive agreement with consensus EIA result was only 65%. Another WCL western immunoblot with purified extracts of Osp C and VlsE, the Trinity Biotech EU Lyme + VlsE IgG Western Blot had a PPV of 92% while the recombinant line blot from EUROIMMUN, the Anti-Borrelia (IgG) EUROLINE-RN-AT, demonstrated a significantly reduced PPV of 70% with some non-specific reactions in sera containing antibodies to Leptospira species, Helicobacter pylori and Treponema pallidum. The use of recombinant antigens in EIA for LB IgG screening significantly improves the predictive values of serological results above those of WCL antigen EIA. Second tier WCS western immunoblots offer high PPVs, especially with added specific purified proteins, more so than in one recombinant line blot.

Evaluation of eight anti-rubella virus immunoglobulin g immunoassays that report results in international units per milliliter.

An evaluation of anti-rubella virus immunoglobulin G (IgG) immunoassays that report in international units per milliliter (IU/ml) was performed to determine their analytical performance and the degree of correlation of the test results. A total of 321 samples were characterized based on results from a hemagglutination inhibition assay. The 48 negative and 273 positive samples were used to determine the sensitivity and specificity of the assays. When equivocal results were interpreted as reactive, the sensitivity of the immunoassays ranged from 98.9 to 99.9% and the specificity ranged from 77.1 to 95.8%. All assays had positive and negative delta values of less than 2. A significant difference between the mean results of all assays was demonstrated by analysis of variance. However, post hoc analysis showed there was good correlation in the mean results expressed in IU/ml between some of the assays. Our results show the level of standardization between anti-rubella virus IgG immunoassays reporting results expressed as IU/ml has improved since a previous study in 1992, but further improvement is required.

Culture-negative endocarditis due to Houston Complex Bartonella henselae acquired in Noumea, New Caledonia.

A 44-year-old man with a bioprosthetic aortic valve suffered destructive endocarditis with severe embolic disease due to Bartonella henselae infection. Multilocus sequence typing was successfully performed with crude preparations of operative tissue as templates, and the infecting organism was determined to be typical of the Houston clonal group, although it was never cultured from blood or tissue. This is the first report of B. henselae infection in the South Pacific, and it reminds one that B. henselae is a cause of potentially lethal culture-negative endocarditis which may respond poorly to conventional empirical therapy. Nothing is known of the epidemiology of the infection in this region, but it is likely to be common and to contain representatives of both major clonal complexes. This study emphasizes the ease with which multilocus sequence typing can be used directly with tissue, which is important because of suggestions of strain-dependent clinical outcomes.

Evaluation of a novel commercial enzyme-linked immunosorbent assay detecting Coxiella burnetii-specific immunoglobulin G for Q fever prevaccination screening and diagnosis.

A novel commercially available enzyme-linked immunosorbent assay (ELISA) for prevaccination screening and diagnosis of Q fever (PanBio Coxiella burnetii immunoglobulin G [IgG] ELISA) was compared to the complement fixation test (CFT), and the indirect fluorescent-antibody test (IFAT) was used to resolve discrepant results between the other two tests. A total of 214 serum samples was tested. The ELISA demonstrated a specificity of 96% (46 of 48 samples) and a sensitivity of 71% (95 of 134 samples). Of the six serum pairs showing CFT seroconversion, three pairs showed a corresponding ELISA seroconversion. No cross-reactivity was observed in the ELISA with serum samples from patients with mycoplasma, brucella, and chlamydia infections. One of the 13 patients with leptospirosis demonstrated a positive result in the ELISA but not in the CFT or the IFAT, and Legionella pneumophila serogroup 4 antibody was found in one of the two sera that were false-positive by ELISA. The results presented in this study suggest that the PanBio Q fever IgG ELISA is a specific alternative method for prevaccination testing and an aid for the diagnosis of Q fever. This test is suitable for use as a screening assay, with CFT and/or IFAT used to confirm negative results.