Performance evaluation of TRUPCR® HBV Real-time PCR assay for Hepatitis B virus DNA quantification in clinical samples: report from a tertiary care liver centre

Simultaneous detection of human norovirus GI, GII and SARS-CoV-2 by a quantitative one-step triplex RT-qPCR

Background

There are many similarities in the clinical manifestations of human norovirus and SARS-CoV-2 infections, and nucleic acid detection is the gold standard for diagnosing both diseases. In order to expedite the identification of norovirus and SARS-CoV-2, a quantitative one-step triplex reverse transcription PCR (RT-qPCR) method was designed in this paper.

Methods

A one-step triplex RT-qPCR assay was developed for simultaneous detection and differentiation of human norovirus GI (NoV-GI), GII (NoV-GII) and SARS-CoV-2 from fecal specimens.

Results

The triplex RT-qPCR assay had high detection reproducibility (CV < 1%) and sensitivity. The lower limits of detection (LLOD95) of the triplex RT-qPCR assay for each target site were 128.5-172.8 copies/mL, and LLOD95 of the singleplex RT-qPCR assay were 110.3-142.0 copies/mL. Meanwhile, among the detection of clinical oropharyngeal swabs and fecal specimens, the results of the singleplex and triplex RT-qPCR assay showed high agreement.

Conclusion

The triplex RT-qPCR assay for simultaneous detection of NoV-GI, NoV-GII and SARS-CoV-2 from fecal specimens has high clinical application value.

Occult Hepatitis B Virus Infection and Its Risks of Cryptic Transmission in Southern Ethiopia

BACKGROUND

The detection of hepatitis B virus surface antigen (HBsAg) in serum remains the mainstay in diagnosing and screening of hepatitis B virus (HBV) in most developing countries. The absence of HBsAg in the blood may not indicate the absence of circulating HBV and might be infectious. Thus, this study aimed to estimate the burden and its cryptic transmission risks of occult hepatitis B infection (OBI) among HBsAg negative healthy individuals in Southern Ethiopia.

METHODS

A community-based cross-sectional study was conducted from September 2020 to January 2021. Serum samples were collected and assayed for HBsAg and HBV core antibody (anti-HBc) seromarkers using enzyme-linked immunosorbent assay (ELISA). In anti-HBc positive samples, HBV DNA was detected using real-time polymerase chain reaction (RT-PCR). Data were entered into Epi-Data version 3.1, cleaned, and analyzed using SPSS version 21.0. Descriptive and logistic regression analyses were employed. Statistical significance was decided at p < 0.05.

RESULTS

A total of 346 were individuals included in this study; 34 (9.8%) were tested positive for HBsAg. The rest 312 (90.2%) negatively tested were further assayed for anti-HBc, and 115 (36.7%) were found positive implying previous exposure to HBV, and 21 (18.3%) out of 115 anti-HBc positives had HBV DNA signifying OBI. The HBV DNA concentration below 200 IU/mL was 85.7%. A high rate of OBI was observed among individuals who had multiple sexual contacts, a family history of hepatitis, and tattooing.

CONCLUSION

In this study, the prevalence of OBI is high. This indicates the burden of HBV is considerable since screening is exclusively dependent on HBsAg which will not eliminate the possibility of residual cryptic transmission through blood donation, organ transplantation, perinatal transmission, and other contacts. Our results demonstrate that nucleic acid-based testing (NAT) should be an essential part of screening to prevent missing OBI.

Accurate nucleic acid quantification in a single sample tube without the need for calibration

Convenient and accurate nucleic acid quantification (NAQ) is crucial to clinical diagnosis, forensic medicine, veterinary medicine and food analysis. However, traditional NAQ relies on the preparation of a laborious, time-consuming and expensive calibration curve, which would also propagate pipette errors through serially dilutions. Besides, traditional NAQ is run in different tubes, which introduces bias from random tube-to-tube variations and is unable to detect inhibitors from biological samples. To solve these problems, a single-tube quantitative PCR (stqPCR) technique is proposed which enables accurate quantification without the need for a calibration curve. In this method, an internal quantitative standard DNA (IQS-DNA) for quantification was screened out by co-amplification with the target DNA. Then the difference between the quantification cycle value (ΔCq) of the IQS-DNA and the target DNA was used for NAQ. The method permitted high accuracy quantification with reliable data for concentrations in plasmid, serum standard, and clinical samples being confirmed (R² values of 0.9951, 0.9889, and 0.9727, slope values of 1.011, 1.028, and 0.9327, and intercept values of -0.06037, -0.1486, and 0.3325, respectively). Accurate NAQ could also be achieved by stqPCR even though inhibitors were present in a sample; however, in the case of using a commercial assay kit, satisfactory performance was only attained after the same sample was diluted some 32-fold. Moreover, integration of the present method into a microfluidic system could achieve super-fast NAQ in less than 30 min and achieve super-fast "sample in, quantitative answer out" testing in less than 40 min. Thus, the stqPCR method present here would promote the development of NAQ in the laboratory and on site.

Rapid and sensitive detection of hepatitis B virus by lateral flow recombinase polymerase amplification assay

Hepatitis B virus (HBV) infection is a major public health priority. In the present study, a lateral flow strip combined with the recombinase polymerase amplification (LF-RPA) assay was developed and evaluated for rapid HBV detection. A primer/probe pair targeting the conserved region of the HBV genome was designed and applied to the LF-RPA. TheRPA was achieved at the isothermal temperature of 39℃ for 30 min, and the RPA products were detected using the LF test. DNA extraction, RPA reaction and endpoint detection will take about 70 min. The LF-RPA assay could detect HBV at as low as 10 copies/reaction, with no cross-reactions with other common pathogens. The LF-RPA assay was performed on 85 samples. Of these, 36 samples tested HBV positive, whereas 49 were negative. Similar results were obtained using the conventional polymerase chain reaction method. Thus, the newly developed LF-RPA assay can be an improved diagnostic tool for rapid and simple HBV detection.