Investigation of occult hepatitis B virus infection in anti-hbc positive patients from a liver clinic.

Occult hepatitis B infection (OBI) is manifested by presence of very low levels (<200IU/mL) of Hepatitis B viral DNA (HBV DNA) in the blood and the liver while exhibiting undetectable HBV surface antigen (HBsAg). The molecular mechanisms underlying this occurrence are still not completely understood. This study investigated the prevalence of OBI in a high-risk Australian population and compared the HBV S gene sequences of our cohort with reference sequences. Serum from HBV DNA positive, HBsAg negative, and hepatitis B core antibody (anti-HBc) positive patients (study cohort) were obtained from samples tested at SEALS Serology Laboratory using the Abbott Architect, as part of screening and diagnostic testing. From a total of 228,108 samples reviewed, 1,451 patients were tested for all three OBI markers. Only 10 patients (0.69%) out of the 1,451 patients were found to fit the selection criteria for OBI. Sequence analysis of the HBV S gene from 5 suspected OBI infected patients showed increased sequence variability in the 'a' epitope of the major hydrophilic region compared to reference sequences. In addition, a total of eight consistent nucleotide substitutions resulting in seven amino acid changes were observed, and three patients had truncated S gene sequence. These mutations appeared to be stable and may result in alterations in HBsAg conformation. These may negatively impact the affinity of hepatitis B surface antibody (anti-HBs) and may explain the false negative results in serological HBV diagnosis. These changes may also enable the virus to persist in the liver by evading immune surveillance. Further studies on a bigger cohort are required to determine whether these amino acid variations have been acquired in the process of immune escape and serve as markers of OBI.

The reliability of HBV core antibody in serological screening for hepatitis B virus.

INTRODUCTION: Accurate diagnosis of hepatitis B virus (HBV) infection is essential for infection control, treatment and screening of potential blood, organ and tissue donors. We assessed the sensitivity of the HBsAg and HBcAb as screening assays alone and in combination for detecting HBV infection in a series of Australian patients. The performance of the Architect (Abbott Diagnostics, Germany) and the Elecsys (Roche Diagnostics, Germany) platforms were assessed for detection of HBcAb. METHODS: There were 2778 blood samples assessed using the COBAS Ampliprep/TaqMan test for HBV DNA, of which 331 sera had concurrent HBV serology testing. This allowed determination of the correlation between HBV DNA and different serological markers. Of the 331 sera, 260 had sufficient residual volume to be retested for HBcAb using both Elecsys and the Architect assays. RESULTS: Of the 331 patients, one (0.3%) was negative by the Architect Anti-HBc II assay, in the presence of HBV DNA and positive HBsAg, consistent with recent infection. Positive HBcAb in the absence of HBV DNA was found in 67 of 331 (20.2%) patients. Of these, 18 of 67 had isolated HBcAb with negative results on all other tests, with 12 of 18 (3.6%) demonstrating low HBcAb signals on chemiluminscent microparticle assay. No cases of detectable HBV DNA in the presence of negative serology were found. When the HBcAb was used as a marker for past exposure or chronic HBV infection, the Architect Anti-HBc II assay demonstrated sensitivity and specificity of 98% and 79.9%, respectively, compared to 90% and 78.9%, respectively, for the Elecsys Anti-HBc assay. The combination of the Architect Anti-HBc II and HBsAg assays, as per conventional solid organ donor and recipient screening protocols, had 90% specificity and 100% sensitivity for determining HBV infection. CONCLUSION: This study shows that the use of combined HBsAg and HBcAb is sensitive and reliable for screening and predicting HBV nucleic acid test (NAT) positivity, whereas HBcAb alone missed an acute infection in this study population. There were no significant differences detectable between the Architect and the Elecsys HBcAb assays (p=0.001), suggesting laboratories should assess individual assays in the local population before use as screening tests.

Infectious disease screening of blood specimens collected post-mortem provides comparable results to pre-mortem specimens.

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.

Stability of hepatitis C virus, HIV, and hepatitis B virus nucleic acids in plasma samples after long-term storage at -20°C and -70°C.

The storage of biological samples may affect detection of viral nucleic acid, yet the stability of viral nucleic acid at standard laboratory storage temperatures (-70°C and -20°C) has not been comprehensively assessed. Deterioration of viral RNA and DNA during storage may affect the detection of viruses, thus leading to an increased likelihood of false-negative results on diagnostic testing. The viral loads of 99 hepatitis C virus (HCV), 41 HIV, and 101 hepatitis B virus (HBV) patient samples were measured before and after storage at -20°C and -70°C for up to 9.1 years using Versant branched DNA assays, Cobas Monitor assays, and/or AmpliPrep/AmpliScreen assays. Clinical samples stored at -20°C for up to 1.2 years and at -70°C for up to 9 years showed a statistically significant difference from baseline with respect to HCV RNA titer, although this difference was not greater than 0.5 log(10) unit. The concentration of HIV RNA in clinical samples stored at -20°C for 2.3 years and at -70°C for up to 9.1 years did not differ significantly from the baseline viral load. HBV DNA-positive clinical samples stored at -20°C for up to 5 years and at -70°C for up to 4 years differed significantly in viral load. In all studies, however, the loss of viral load of HCV, HIV, or HBV in clinical samples tested after storage at -20°C and -70°C for up to 9 years ranged from 0.01 to 0.35 log(10) IU/ml and did not exceed 0.5 log(10), which is the estimated intra-assay variation for molecular tests. Hence, the loss was considered of minimal clinical impact and adequate for the detection of HCV, HIV-1, and HBV nucleic acids using nucleic acid assays for the assessment of the infectious risk of cell, blood, and tissue donors.

Effect of low-level HCV viraemia at week 24 on HCV treatment response in genotype 1 patients.

BACKGROUND: We examined the detection of low-level viraemia at week 24 as a predictor of sustained virological response (SVR) and viral relapse/breakthrough, and the agreement between the Roche Cobas TaqMan™ HCV RNA assay (TaqMan) and Roche Cobas(®) Amplicor HCV qualitative assay (Amplicor; both Roche Molecular Diagnostics, Pleasanton, CA, USA) for detection of low-level viraemia. METHODS: A total of 871 treatment-naive HCV genotype 1 patients participating in an induction-dose pegylated interferon therapy study had virological responses assessed using TaqMan. A total of 151 patients with HCV RNA levels ≤500 IU/ml had samples tested in parallel using the Amplicor and TaqMan assays. RESULTS: SVR was significantly lower and relapse/breakthrough significantly higher in patients with low-level residual viraemia at week 24 compared with those who had undetectable viraemia: SVR was 72%, 29% and 14% (P<0.0001) and relapse/breakthrough 28%, 71% and 86% (P<0.0001) in patients with viraemia that was undetectable, detectable <15 IU/ml and detectable 15-<50 IU/ml, respectively, at week 24. The negative predictive value (NPV) for a week-24 virological response for SVR was 86%, 90% and 90% using TaqMan cutoffs of undetectable, <15 IU/ml and <50 IU/ml, respectively. The percentage agreement between Amplicor and TaqMan was similarly high for TaqMan cutoffs of 50 IU/ml and 15 IU/ml, but lower for undetectable viraemia (83%, 83% and 70%, respectively). CONCLUSIONS: These data emphasize the importance of achieving undetectable HCV RNA during pegylated interferon therapy to maximize SVR; however, the current 24-week stopping rule of undetectable HCV RNA appears too stringent when using sensitive PCR assays given the observed lower NPV for SVR using the TaqMan undetectable cutoff. Our data also suggest that a TaqMan <15 IU/ml result is comparable to an Amplicor-negative result (that is, below the assay cutoff value) when monitoring viral response.

A commercial ELISA detects high levels of human H5 antibody but cross-reacts with influenza A antibodies.

BACKGROUND AND OBJECTIVES: Commercial serological assays to determine influenza A H5N1 infection are available, although the accuracy and reproducibility of these are not reported in detail. This study aimed to assess the validity of a commercial ELISA H5 hemagglutinin (HA) antibody kit. STUDY DESIGN: A commercial ELISA for detection of antibodies towards influenza A H5 HA was evaluated using human sera from vaccinated individuals. The ELISA was used to screen 304 sera with elevated influenza A complement fixation titres collected between the period 1995-2007. RESULTS AND CONCLUSIONS: The ELISA was found to be accurate for sera with high levels of anti-H5 antibodies, and would be useful in clinical settings where a rapid result is required. Thirteen of the stored sera were positive using the ELISA, but were confirmed as negative for H5N1 exposure using further serological tests. Absorption studies suggested that antibodies towards seasonal H3N2 and H1N1 influenza may cross-react with H5 antigen, giving false positive results with the ELISA.

Proficiency of nucleic acid tests for avian influenza viruses, Australasia.

An avian influenza quality assurance program was used to provide information for laboratories on the sensitivity and specificity of their avian influenza nucleic acid testing. Most laboratories were able to correctly detect clinically relevant amounts of influenza virus (H5N1), and results improved as each subsequent panel was tested.

Comparison of a novel HPV test with the Hybrid Capture II (hcII) and a reference PCR method shows high specificity and positive predictive value for 13 high-risk human papillomavirus infections.

BACKGROUND: It is well established that human papillomavirus (HPV) infection is highly related to the development of precursor lesions of cervical cancer and uterine cancers. However, for a pre-cancerous lesion to develop, a persistent infection with a high-risk type HPV is necessary. The Digene Hybrid Capture II (hcII) assay is the only FDA approved method used in conjunction with cytology for HPV screening of women older than 30. The hcII has moderate sensitivity (64.7%) and is dependent on the cellular content of samples, rendering occasionally false positive and false negative results. OBJECTIVE: This study aims to evaluate the performance of a new HPV diagnostic kit (High-Risk HPV detection kit, manufactured by Human Genetic Signatures (HGS), Sydney, Australia). METHODS: The method under evaluation was assessed by comparing the results obtained from testing 834 cervical specimens with the HGS method and the Digene hcII method, using genotyping as the reference standard. RESULTS: Results of the study showed that the specificity and positive predictive value of the HGS High-Risk HPV detection test are significantly greater than those of the Digene hcII test. Overall the HGS HPV assay provides a more accurate system for the detection of high-risk HPV strains, with simpler technical use compared with PCR-sequencing methods.

Comparison of two rapid influenza A/B test kits with reference methods showing high specificity and sensitivity for influenza A infection.

The rapid detection of influenza viruses is important for forming preventative strategies, directing initiation of anti-viral therapy, detecting potential avian influenza viruses, and excluding influenza-like pathogens, such as SARS. The ImmunoCard STAT! Flu A and B Plus test (Meridian Bioscience, Cincinnati, OH) is a new point of care (POC) test utilizing influenza-specific monoclonal antibodies for rapid diagnosis. The performance of this assay was compared to the established POC Binax NowFlu A and NowFlu B test, and the reference diagnostic standards of viral culture, indirect immunofluorescence (IFA), and RT-PCR where appropriate. Testing of nasopharyngeal aspirates (NPA) from children, throat swabs, and nasal swabs from adults indicated ImmunoCard STAT! specificity of 98% and 100% for influenza A and B, respectively in 224 specimens. The Binax test showed specificity of 99% and 100%, respectively for influenza A and B. Sensitivity results were identical for both rapid detection kits (80% and 47% for Flu A and B, respectively). Overall results were very similar for both testing devices with the advantage of ImmunoCard STAT! Flu A and B Plus test detecting influenza A and B with sharp and easy to read results.