Comparison of currently available assays for detection of hepatitis B virus DNA in the routine diagnostic laboratory

Diagnostic validity of the chemiluminescent method compared to polymerase chain reaction for hepatitis B virus detection in the routine clinical diagnostic laboratory

Background:

Hepatitis B virus (HBV) is the most common significant chronic viral infection world-wide. Hepatitis B surface antigen (HBsAg) has been the principal target for laboratory testing to identify active infection by HBV. We aimed to find out diagnostic validity of the Liaison chemiluminescent method compared to the polymerase chain reaction (PCR) method for HBV detection in the routine clinical diagnostic laboratory.

Materials and Methods:

From 350 patients suspicious of having infection with HBV, serum samples were separated and used for testing HBsAg by two methods of Liaison chemiluminescent immunoassay, with HBsAg confirmatory test and PCR method.

Results:

According to the PCR results as assumed as gold standard method with 100% sensitivity and specificity, detection rate sensitivity of chemiluminescent with confirmatory test was 96% and its specificity was 100%, and for chemiluminescent without confirmatory test sensitivity and specificity were 100% and 70%, respectively. Also for chemiluminescent with confirmatory test, positive predictive value (PPV) was 100% and its negative predictive value (NPV) was 97%, compared to chemiluminescent without confirmatory test with PPV and NPV equal to 71% and 100%, respectively.

Conclusions:

It is possible to conclude that in the majority of the HBV cases, the diagnostic value of chemiluminescent method compared to the PCR method is acceptable, except in low indexes positive cases that need further investigation with the PCR method.

Protocol for the use of light upon extension real-time PCR for the determination of viral load in HBV infection

Real-time PCR has engendered wide acceptance for quantitation of hepatitis B virus (HBV) DNA in the blood due to its improved rapidity, sensitivity, reproducibility, and reduced contamination. Here we describe a cost-effective and highly sensitive HBV real-time quantitative assay based on the light upon extension real-time PCR platform and a simple and reliable HBV DNA preparation method using silica-coated magnetic beads.

Nuclease-resistant double-stranded DNA controls or standards for hepatitis B virus nucleic acid amplification assays

BACKGROUND

Identical blood samples tested using different kits can give markedly different hepatitis B virus (HBV) DNA levels, which can cause difficulty in the interpretation of viral load. A universal double-stranded DNA control or standard that can be used in all commercial HBV DNA nucleic acid amplification assay kits is urgently needed. By aligning all HBV genotypes (A-H), we found that the surface antigen gene and precore-core gene regions of HBV are the most conserved regions among the different HBV genotypes. We constructed a chimeric fragment by overlapping extension polymerase chain reaction and obtained a 1,349-bp HBVC+S fragment. We then packaged the fragment into lambda phages using a traditional lambda phage cloning procedure.

RESULTS

The obtained armored DNA was resistant to DNase I digestion and was stable, noninfectious to humans, and could be easily extracted using commercial kits. More importantly, the armored DNA may be used with all HBV DNA nucleic acid amplification assay kits.

CONCLUSIONS

The lambda phage packaging system can be used as an excellent expression platform for armored DNA. The obtained armored DNA possessed all characteristics of an excellent positive control or standard. In addition, this armored DNA is likely to be appropriate for all commercial HBV DNA nucleic acid amplification detection kits. Thus, the constructed armored DNA can probably be used as a universal positive control or standard in HBV DNA assays.

A novel real-time PCR assay for determination of viral loads in person infected with hepatitis B virus

A novel LUX (Light Upon eXtension) primer-based real-time PCR assay was developed and evaluated in this study, which was designed to provide a cost-effective, specific and highly sensitive method for viral load determination of hepatitis B virus (HBV). The assay employed an effective and rapid nucleic acid extraction system based on magnetic beads. To evaluate its efficacy, this new viral DNA preparation method was compared with QIAamp Blood Mini Kit and the results showed a good correlation (r=0.971; P<0.001). The performance of the LUX real-time assay was validated by testing serial dilutions of HBV plasmid DNA (5 to 5 x 10(8)copies/reaction) and a good linear relationship was obtained between the Ct values and the log(10) concentration of the HBV DNA. The assay possessed high sensitivity and the detection limit of this system was as few as 25 copies/ml of serum. A total of 91 positive serum samples were detected to evaluate further the assay and the high specificity was confirmed by melting curve analysis. This assay provides an ideal tool for monitoring the treatment efficacy and studying the relationship between HBV viral load and the stage of disease.

Serum antibodies to periodontal bacteria as diagnostic markers of periodontitis

BACKGROUND

Assessment of periodontal conditions in epidemiologic studies usually requires a clinical examination, which is resource-intensive. We investigated the ability of serum immunoglobulin G (IgG) antibodies to periodontal bacteria to reflect clinical periodontal status.

METHODS

We used checkerboard immunoblotting to assess serum IgG levels to 19 species, including established/putative periodontal pathogens and non-pathogenic bacteria, in 5,747 dentate adults aged > or = 40 years who participated in the third National Health and Nutrition Examination Survey between 1988 and 1994. Three earlier described alternative definitions of periodontitis were used, based on specific combinations of probing depth and attachment level values. Optimized elevated titer thresholds and corresponding sensitivities and specificities were calculated for each definition. Titers significantly associated with periodontitis were identified in univariable and multivariable logistic regression models. Parsimonious models were subsequently developed using age, gender, race/ethnicity, education, smoking, and diagnosed diabetes.

RESULTS

In unadjusted models, high titers to Porphyromonas gingivalis were most strongly associated with periodontitis across all definitions (odds ratio, 2.07 to 2.74; P <0.05). In parsimonious models including demographic data, smoking, and diagnosed diabetes, high P. gingivalis titers were consistently associated with periodontitis, whereas high Eubacterium nodatum titers were associated with periodontal health in two of three definitions. Receiver operating characteristic curves for the parsimonious multivariable models showed that the area under the curve ranged between 0.72 and 0.78.

CONCLUSIONS

Serum IgG titers to selected periodontal species, combined with demographic and behavioral characteristics, resulted in a moderately accurate classification of periodontal status in epidemiologic studies. The external validity of these findings must be examined further.

Development and evaluation of real-time loop-mediated isothermal amplification for hepatitis B virus DNA quantification: a new tool for HBV management

BACKGROUND

Accurate quantitation of hepatitis B viral load is a critical aspect in screening and monitoring HBV infection.

OBJECTIVES

We used loop-mediated isothermal amplification (LAMP) to develop a real-time fluorogenic (RtF-LAMP) protocol to quantitate HBV DNA. Quantitative analysis was obtained by measuring time-to-positive (TTP), a biomarker similar to cycle threshold (Ct) in real-time PCR.

STUDY DESIGN

Sensitivity, specificity, reproducibility, and dynamic range for RtF-LAMP were evaluated using molecular and biological standards. Four hundred and two patient samples were then used to compare the performance of RtF-LAMP to a commercial real-time PCR assay (DaAn Gene Co, China).

RESULTS

The lower detection limit (LDL) of RtF-LAMP by Probit analysis at the 95% detection level was 210 copies/ml, and the dynamic range was 8 orders of magnitude. The conversion factor for results obtained with the RtF-LAMP assay was 1 IU/ml equals to 4.4 copies/ml. Coefficients of variation (CV) reflected low intra-assay and inter-assay variability (4.24-12.11%). In a large number of serum samples, there was excellent an correlation between RtF-LAMP and real-time PCR (R(2)=0.96). There was a good agreement between the two tests except at the detection cutoff of the real-time PCR assay.

CONCLUSION

Our RtF-LAMP protocol appears to be precise, accurate and rapid. It could be a valuable tool for the detection of HBV in large clinical and epidemiological studies.