Current serological methods for the diagnosis of Epstein-Barr virus (EBV) infection still differentiate poorly between primary infection and reactivation. This is particularly true when IgG and IgM antibodies are present simultaneously and only a single serum sample is provided for analysis. The demonstration of the IgG avidity state has the potential to distinguish recent from past or reactivated infection. An analysis of the kinetics of avidity maturation of anti-VCA antibodies in primary EBV infection was undertaken with longitudinally collected sets of sera from 28 well-characterised EBV cases and in sera from 35 cases with previous EBV infection and recent primary infection due to HIV, CMV, or hepatitis A. Antibodies directed against the viral capsid antigen (VCA) and Epstein-Barr nuclear antigen (EBNA-1) were sought, using a commercial enzyme immunoassay (EIA). In parallel with standard IgG anti-VCA detection, serum was incubated with 8 M urea to disrupt low-avidity complexes to allow calculation of the percentage avidity. In cases with primary EBV infection, the mean avidity rose from 54% at 6 weeks to 82% by 28 weeks after the onset of symptoms, but remained lower than that of the control sera (96%). The addition of the avidity measurement improved the sensitivity of IgG and IgM anti-VCA testing in diagnosis of primary EBV infection from 93% to 100%. The specificity of IgM anti-VCA testing alone was poor, with 14 of 35 cases (49%) demonstrating false-positive results, but it improved to 97% by the demonstration of high-avidity IgG anti-VCA. The combination of negative IgG anti-EBNA and low-avidity IgG anti-VCA had a sensitivity and specificity of 100%. The routine addition of IgG anti-VCA avidity estimation to diagnostic EBV serology is recommended.

Serology assays for standard screening are optimised for use with sera collected from living adults and children. Because of potential changes in the vascular compartments after death, methods used for screening sera from cadaveric organ donors need to be validated before testing these specimens. Serum was separated from blood collected from cadaveric donors within 24 h of death and biochemical parameters measured to detect dilution of protein and haemolysis. In order to demonstrate if any inhibitors that might interfere with the assays were present, pre and post-mortem specimens were spiked with aliquots of human immunodeficiency virus (HIV), hepatitis C virus (HCV), hepatitis B virus (HBV), human T-cell Lymphotropic Virus (HTLV) and T. pallidum-positive sera. Comparison of serum from living subjects with serum obtained post-mortem showed that while the concentration of total protein decreased, concentrations of albumin, immunoglobulin G (IgG) and immunoglobulin M (IgM) remained unchanged. The degree of haemolysis, as measured by free haemoglobin, was within the limits accepted for the Architect analyser. Spiking of pre- and post-mortem specimens with aliquots of HIV, HCV, HBV, HTLV and T. pallidum-positive sera showed no statistical difference in the signal between pre-mortem and post-mortem results when tested on the Abbott Architect analyser. Positive results were obtained in each of a further nine subjects who had tested positive for HIV (n=1), HCV (n=8), HBV (n=1) on pre-mortem serological testing. These findings suggest that the sensitivity of the Abbott Architect serological screening tests is not significantly affected in specimens collected within 24 h of the cessation of life.

A rapid diagnosis is considered important in HIV care. In 138,911 testing episodes with the Abbott Architect HIV Ag/Ab Combo assay (3,705 reactive samples), a signal-to-cutoff ratio of >151.17 had a positive predictive value of 100% and a sensitivity of 67.4% for the detection of subsequently confirmed HIV infection. We suggest that results higher than this signal-to-cutoff ratio threshold may be reported to clinicians before the completion of confirmatory testing. HIV testing algorithms aim to minimize the time to confirmation of the diagnosis with maximum sensitivity and specificity. The Abbott Architect HIV Ag/Ab Combo assay (Abbott Combo; Abbott Laboratories, Abbott Park, IL, USA) is a chemiluminescent microparticle immunoassay that simultaneously detects HIV-1 p24 antigen (Ag), HIV-1 gp41 antibody (Ab), and HIV-2 gp36 Ab. The magnitude of the chemiluminescent signal is reported as a signal-to-cutoff (S/CO) ratio. It is a commonly used screening test, as it has a sensitivity and specificity of Ͼ99% and Ͼ98%, respectively (1-3).Confirmatory testing is typically undertaken with highly specific Western blot (WB) analysis or, more recently in some countries, including the United States, an HIV-1-HIV-2 differentiation immunoassay that proceeds to a qualitative nucleic acid test for any discordant case (4).We hypothesized that the positive predictive value (PPV) of the Abbott Combo assay for HIV-1 infection increases with the S/CO ratio and that test results higher than a specific S/CO ratio can be rapidly communicated to clinicians without awaiting supplemental test results. Such a threshold may also inform the use of single testing algorithms in resource-poor settings. As the PPV is dependent on the prevalence of infection in the population sampled, the objective of the study was to identify an S/CO ratio with a 100% PPV for HIV-1 infection in Australia, which has a low HIV prevalence of 0.15% (5).Other studies with small samples have suggested a relationship between the S/CO ratio in HIV Ag/Ab assays and confirmed HIV infection or the HIV viral load (VL) (1, 6-8). As the somewhat time-consuming HIV WB test is the currently approved confirmatory test in Australia, we assessed the positive predictive value of the Abbott Combo assay in this low-prevalence population.We retrospectively analyzed all Abbott Combo testing episodes from a large serology diagnostic laboratory in Sydney, Australia, between March 2006 and March 2014. All serum samples were tested with the Abbott Combo assay, and reactive results were tested in duplicate after centrifugation at 10,000 ϫ g for 10 min. If at least one of the repeat tests was reactive, three supplemental tests were performed: a p24 Ag enzyme immunoassay (EIA) with confirmatory neutralization (Vironostika HIV-1 Ag [bioMérieux, Marcy l'Etoile, France] or Genscreen HIV-1 Ag [Bio-Rad, CA, USA]), a WB test (MP Diagnostics HIV-1/2 Blot 2.2; MP Biomedicals, CA, USA), and an HIV-1 Ab particle agglutination assay (Serodia-HIV; Fujirebio, Tokyo, Japan). HIV VL testing was performed wit...

dDiagnosis of acute HIV is done by patient history and examination and testing of RNA, proviral DNA, and serology using fourthgeneration antigen/antibody detection assays. We describe an HIV-1 primary infection with a second diagnostic window of 18 to 34 days on a fourth-generation immunoassay, which would have been missed using some current algorithms. Caution must be exercised when fourth-generation HIV-1 immunoassays are interpreted in isolation, and additional testing should be considered depending on patient risk assessment. CASE REPORTA 43-year-old circumcised Caucasian man who regularly attended a sexually transmitted infection (STI) clinic presented for testing, reporting a recent mild flu-like illness. His sexual risk factors included regular local bathhouse contact, mostly unprotected oral sex, unprotected insertive anal sex over several years, and recent unprotected receptive anal sex.

A multicentre trial was conducted to evaluate a new test for anti-gliadin antibodies (AGA) in serum (Coeliac Screening Kit, CSK, Medical Innovations Limited, Artarmon, NSW, Australia). The test showed excellent reproducibility for both anti-gliadin IgA and IgG detection. The average intraassay coefficient of variation (CV) was 3.0% for IgA and 2.4% for IgG (n = 6), while the average interassay CV was 6.4% for IgA and 4.3% for IgG (n = 3). By defining a positive test as both IgA and IgG elevated, a sensitivity of 93% in untreated coeliacs (n = 75) was observed. The corresponding specificities in healthy adults (n = 130) and healthy children (n = 77) were > 99% and 100% respectively, while in patients with other gastrointestinal disorders (disease controls) the specificity was 94% (n = 129). The test was also useful in monitoring patients, with anti-gliadin IgA and IgG falling for up to a year after commencing a gluten-free diet (GFD) (12 adults). In some patients however, antibody levels did not reach the normal cutpoint after many months on a GFD, which may reflect the patients' poor adherence to their gluten free diet. The test was superior to the Pharmacia anti-gliadin ELISA, and should be useful as an aid to the diagnosis of coeliac disease, as well as in the follow-up of treated patients.

Both HCV and probable non-A-E virus(es) were important causes of acute NANB hepatitis during the early 1970s.

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