Elsevier

Journal of Clinical Virology

Volume 72, November 2015, Pages 20-24
Journal of Clinical Virology

Hepatitis B viral load in dried blood spots: A validation study in Zambia

https://doi.org/10.1016/j.jcv.2015.08.019Get rights and content

Highlights

  • Dried blood spots (DBS) were tested in a Zambian lab for hepatitis B viral load.

  • There was strong agreement between HBV viral loads in DBS and plasma samples.

  • DBS viral loads were on average 1.5 log IU/ml lower than plasma viral loads.

  • HBV was detected in DBS 98.2% of the time at a plasma viral load ≥2,000 IU/ml.

Abstract

Background

Access to hepatitis B viral load (VL) testing is poor in sub-Saharan Africa (SSA) due to economic and logistical reasons.

Objectives

To demonstrate the feasibility of testing dried blood spots (DBS) for hepatitis B virus (HBV) VL in a laboratory in Lusaka, Zambia, and to compare HBV VLs between DBS and plasma samples.

Study design

Paired plasma and DBS samples from HIV-HBV co-infected Zambian adults were analyzed for HBV VL using the COBAS AmpliPrep/COBAS TaqMan HBV test (Version 2.0) and for HBV genotype by direct sequencing. We used Bland-Altman analysis to compare VLs between sample types and by genotype. Logistic regression analysis was conducted to assess the probability of an undetectable DBS result by plasma VL.

Results

Among 68 participants, median age was 34 years, 61.8% were men, and median plasma HBV VL was 3.98 log IU/ml (interquartile range, 2.04–5.95). Among sequenced viruses, 28 were genotype A1 and 27 were genotype E. Bland–Altman plots suggested strong agreement between DBS and plasma VLs. DBS VLs were on average 1.59 log IU/ml lower than plasma with 95% limits of agreement of −2.40 to −0.83 log IU/ml. At a plasma VL ≥2,000 IU/ml, the probability of an undetectable DBS result was 1.8% (95% CI: 0.5–6.6). At plasma VL ≥20,000 IU/ml this probability reduced to 0.2% (95% CI: 0.03–1.7).

Conclusions

In a Zambian laboratory, we observed strong agreement between DBS and plasma VLs and high sensitivity in DBS at plasma VL ≥2,000 IU/ml. As HBV treatment expands, DBS could increase access to HBV VL testing and care in SSA settings.

Section snippets

Background

Worldwide approximately 240 million individuals are chronically infected with hepatitis B virus (HBV), with the highest burden of cases in Asia and sub-Saharan Africa (SSA) [1]. Each year, 650,000 individuals die from complications of chronic HBV infection including decompensated cirrhosis and hepatocellular carcinoma [2]. For individuals with chronic HBV infection, several potent nucleoside/nucleotide analogues can durably suppress viral replication and reduce liver-related complications and

Objectives

Building on prior work in this area, we compared HBV viral loads in paired DBS and plasma samples using commercially available tests in a Zambian laboratory that had experience in HIV viral load and DBS testing.

Study population

HIV-infected adults (18+ years old) who were eligible for antiretroviral therapy, but had not yet initiated, were enrolled in a prospective cohort in two public sector clinics in Zambia’s capital Lusaka, funded through the International Epidemiologic Databases to Evaluate AIDS in Southern Africa [9]. The study’s aim was to evaluate the prevalence, risk factors, and outcomes of liver fibrosis. As part of the enrollment procedures, all participants were screened for hepatitis B virus (HBV)

Results

Of 798 patients screened for HBV infection, 98 (12.2%) were HBsAg-positive. Among HBsAg-positive patients, paired plasma and DBS samples from 68 patients with detectable plasma HBV DNA were included in this study. The median age of patients included in the study was 34 years (interquartile range [IQR], 29–37), 61.8% were men, median CD4+ count was 210 (IQR, 112–378), and 47.0% were hepatitis B e antigen positive. Original plasma samples had a median HBV viral load of 3.98 log IU/ml

Discussion

In a reference laboratory in Lusaka, Zambia, we used commercially available assays to demonstrate the feasibility and performance of HBV viral load testing of DBS samples that were collected by finger stick in field settings. There was a strong agreement between paired DBS and plasma samples over a dynamic range of viral loads for both HBV genotypes A1 and E viruses, the most common ones in Southern Africa. At recommended treatment thresholds, HBV DNA was detectable >98% of the time in DBS.

Funding

Data presented in this paper were supported by the International Epidemiological Databases to Evaluate AIDS in Southern Africa (IeDEA-SA) Collaboration with funding from the National Institute of Allergy and Infectious Diseases (grant number 4U01AI069924) of the National Institutes of Health (NIH). Additional NIH support was provided by the Fogarty International Center (grant number K01TW009998). We also received funding from the HIV Research Trust, Roche Molecular Systems Inc., and the Swiss

Competing interests

Roche Molecular Systems donated some of the laboratory reagents used in this study but did not participate in designing the study, collecting the data, analyzing the data, or writing the manuscript. All authors report no conflicts of interest.

Ethical approval

All participants provided written informed consent.

Acknowledgment

None

References (15)

There are more references available in the full text version of this article.

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    DBS pretreatment is crucial to retrieve the target serological marker or nucleic acid. Various nucleic acid extraction kits can be used prior to detection and quantification of viral genomes or genotype determination.60,62–64 DBSs provide an invaluable tool for large-scale viral hepatitis screening, diagnosis, treatment decision and monitoring in the developing world, because few laboratories have the capacity to perform virological tests and those who can are often distant from rural communities where a large proportion of the population lives.

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