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Detection of hepatitis B Virus surface antigen (HBsAg) is an established method for diagnosing both acute and chronic hepatitis B virus (HBV) infection. In addition to enzyme immunoassays (EIAs), rapid diagnostic tests (RDTs) are available for the detection of HBsAg in resource-poor settings. However, the available RDTs have inadequate sensitivity and therefore are not suitable for diagnosis of patients with low levels of HBsAg and for blood screening. To provide a high-sensitivity RDT, we developed a lateral flow immunoassay (LFIA) for HBsAg utilizing upconverting nanoparticle (UCNP) reporter. The UCNP-LFIA can use whole blood, serum, or plasma and the results can be read in 30 min using a reader device. When compared with a commercial conventional visually read LFIA, the developed UCNP-LFIA had a Limit of Detection (LoD) of 0.1 IU HBsAg/ml in spiked serum, whereas the LoD of the conventional LFIA was 3.2 IU HBsAg/ml. The developed UCNP-LFIA fulfills the WHO criterion for blood screening (LoD ≤ 0.13 IU HBsAg/ml) in terms of LoD. The UCNP-LFIA and conventional LFIA were evaluated with well-characterized sample panels. The UCNP-LFIA detected 20/24 HBsAg-positive samples within the HBsAg Performance Panel and 8/10 samples within the Mixed Titer Performance Panel, whereas the conventional LFIA detected 8/24 and 4/10 samples in these panels, respectively. The performance of the assays was further evaluated with HBsAg-positive (n = 108) and HBsAg-negative (n = 315) patient samples. In comparison with a central laboratory test, UCNP-LFIA showed 95.4% (95% CI: 89.5–98.5%) sensitivity whereas sensitivity of the conventional LFIA was 87.7% (95%CI: 79.9–93.3%).

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Myxovirus resistance protein A (MxA) is a biomarker of interferon-induced gene expression state involved in many viral infections and some autoimmune disorders. It has a variety of potential utilities in clinical diagnostics, including distinguishing between bacterial and viral infections. Currently, MxA-assays are used for monitoring of IFN-β therapy in multiple sclerosis (MS) patients. As a proof-of-concept for rapid quantitative measurement of interferon response, a lateral flow immunoassay (LFIA) with upconverting nanoparticle (UCNP) reporters was developed and evaluated with clinical whole blood samples to assess the potential for a rapid and user-friendly quantitative assay for MxA, since the currently available rapid test for MxA (FebriDX) produces only qualitative result. The high detection sensitivity enabled by the UCNP reporter technology allowed the sample pre-treatment with dilution of whole blood into lysis buffer at a detectable analyte concentration. The assay can be done within 2 hr and the results correlate with the reference MxA-ELISA, which requires an overnight incubation. With 36 samples, R for linear regression was 0.86. The assay detected 96% of the IFN-β responders with 89% specificity using a cut-off level of 100 μg/L for an elevated MxA-concentration. J. Med. Virol. 89:598-605, 2017. © 2016 Wiley Periodicals, Inc.