Assessment of diagnostic and analytic performance of the SD Bioline Dengue Duo test for dengue virus (DENV) infections in an endemic area (Savannakhet province, Lao People's Democratic Republic)

Improving dengue diagnosis and case confirmation in children by combining rapid diagnostic tests, clinical, and laboratory variables

Background

Dengue is the most widely distributed arboviral disease in tropical and subtropical countries. Most suspected cases are diagnosed according to the clinical criteria, and early diagnosis is difficult. Moreover, in underdeveloped countries, several factors continue to challenge the diagnosis and surveillance of dengue cases. This study aimed to design a diagnostic algorithm using rapid diagnostic tests (RDTs), ELISA tests, and clinical and hematological variables to confirm dengue cases in febrile patients in Colombia.

Methods

Altogether, 505 samples were collected. Serum samples were evaluated by RDTs (IgM and IgG antibodies and NS1 antigen), capture IgM and IgG ELISAs, and endpoint hemi-nested RT-PCR assay (qualitative). We statistically analyzed the performance of individual tests to determine the most useful ones to confirm dengue cases accurately.

Results

Individual results for IgM, IgG, and NS1 RDTs yielded lower sensitivity and specificity values than the reference standard. High sensitivity and specificity were obtained after combining IgM and NS1 ELISA results (96.3% and 96.4%) and NS1 RDT plus IgM ELISA results (90.3% and 96.2%), respectively. Adjusted odds ratios (aORs) were calculated for clinical variables and laboratory tests to differentiate dengue from other febrile illnesses (OFI). This approach showed that myalgia, abdominal tenderness, and platelet count were identified with higher sensitivity to confirm dengue cases. IgM RDT and NS1 RDT differentiated dengue cases from OFI. A positive IgM RDT or a positive NS1 RDT combined with specific signs or symptoms confirmed 81.6% of dengue cases. A combination of clinical findings and a positive NS1 RDT or positive ELISA IgM confirmed 90.6% of the cases.

Conclusion

Our findings showed that clinical diagnoses in pediatric population alone cannot confirm true dengue cases and needs to be complemented by laboratory diagnostic tests. We also demonstrate the usefulness of combining clinical criteria with RDTs, suggesting that their implementation with the IgM ELISA test improves dengue case confirmation.

Performance of VIDAS® Diagnostic Tests for the Automated Detection of Dengue Virus NS1 Antigen and of Anti-Dengue Virus IgM and IgG Antibodies: A Multicentre, International Study

Dengue is a serious mosquito-transmitted disease caused by the dengue virus (DENV). Rapid and reliable diagnosis of DENV infection is urgently needed in dengue-endemic regions. We describe here the performance evaluation of the CE-marked VIDAS® dengue immunoassays developed for the automated detection of DENV NS1 antigen and anti-DENV IgM and IgG antibodies. A multicenter concordance study was conducted in 1296 patients from dengue-endemic regions in Asia, Latin America, and Africa. VIDAS® dengue results were compared to those of competitor enzyme-linked immunosorbent assays (ELISA). The VIDAS® dengue assays showed high precision (CV ≤ 10.7%) and limited cross-reactivity (≤15.4%) with other infections. VIDAS® DENGUE NS1 Ag showed high positive and negative percent agreement (92.8% PPA and 91.7% NPA) in acute patients within 0–5 days of symptom onset. VIDAS® Anti-DENGUE IgM and IgG showed a moderate-to-high concordance with ELISA (74.8% to 90.6%) in post-acute and recovery patients. PPA was further improved in combined VIDAS® NS1/IgM (96.4% in 0–5 days acute patients) and IgM/IgG (91.9% in post-acute patients) tests. Altogether, the VIDAS® dengue NS1, IgM, and IgG assays performed well, either alone or in combination, and should be suitable for the accurate diagnosis of DENV infection in dengue-endemic regions.

The Role of NS1 Protein in the Diagnosis of Flavivirus Infections

Nonstructural protein 1 (NS1) is a glycoprotein among the flavivirus genus. It is found in both membrane-associated and soluble secreted forms, has an essential role in viral replication, and modulates the host immune response. NS1 is secreted from infected cells within hours after viral infection, and thus immunodetection of NS1 can be used for early serum diagnosis of dengue fever infections instead of real-time (RT)-PCR. This method is fast, simple, and affordable, and its availability could provide an easy point-of-care testing solution for developing countries. Early studies show that detecting NS1 in cerebrospinal fluid (CSF) samples is possible and can improve the surveillance of patients with dengue-associated neurological diseases. NS1 can be detected postmortem in tissue specimens. It can also be identified using noninvasive methods in urine, saliva, and dried blood spots, extending the availability and effective detection period. Recently, an enzyme-linked immunosorbent assay (ELISA) assay for detecting antibodies directed against Zika virus NS1 has been developed and used for diagnosing Zika infection. This NS1-based assay was significantly more specific than envelope protein-based assays, suggesting that similar assays might be more specific for other flaviviruses as well. This review summarizes the knowledge on flaviviruses' NS1's potential role in antigen and antibody diagnosis.

Performance of the onstructural 1 Antigen Rapid Test for detecting all four DENV serotypes in clinical specimens from Bangkok, Thailand

BACKGROUND

Dengue is an arboviral disease that has a large effect on public health in subtropical and tropical countries. Rapid and accurate detection of dengue infection is necessary for diagnosis and disease management. We previously developed highly sensitive immunochromatographic devices, the TKK 1st and TKK 2nd kits, based on dengue virus (DENV) nonstructural protein 1 detection. However, these TKK kits were evaluated mainly using DENV type 2 clinical specimens collected in Bangladesh, and further validation using clinical specimens of other serotypes was needed.

METHODS

In the present study, one of the TKK kits, TKK 2nd, was evaluated using 10 DENV-1, 10 DENV-2, 4 DENV-3, 16 DENV-4, and 10 zika virus-infected clinical specimens collected in Bangkok, Thailand.

RESULTS

The TKK 2nd kit successfully detected all four DENV serotypes in patient serum specimens and did not show any cross-reactivities against zika virus serum specimens. The IgM and/or IgG anti-DENV antibodies were detected in seven serum specimens, but did not seem to affect the results of antigen detection in the TKK 2nd kit.

CONCLUSION

The results showed that the TKK 2nd kit successfully detected all four DENV serotypes in clinical specimens and confirmed the potential of the kit for dengue diagnosis in endemic countries.

Diagnostic performance of the rapid test for the detection of NS1 antigen and IgM and IgG anti-antibodies against dengue virus

OBJECTIVES

Motivation for the study: search for accessible and efficient new diagnostic alternatives for the detection of the disease caused by the dengue virus. Main findings: good efficiency of the rapid test during the first days of the disease. As well as its high power to discriminate against other similar mosquito-borne diseases such as Zika and Oropuche. Implications: it could be applied as a screening test in endemic regions that do not have equipment or trained personnel to perform sophisticated and/or complex diagnostic tests. Strengthening public health policies in epidemiological surveillance, early diagnosis and timely treatment. To assess the diagnostic performance of the SD dengue DUO rapid test (Inyecta) for the detection of NS1, IgM and IgG in comparison to the ELISA test.

MATERIALS AND METHODS

. This is a diagnostic test evaluation that included 286 serum samples from patients with symptomatology attributable to dengue from endemic areas of Peru. The samples were analyzed by ELISA and the SD dengue DUO rapid test (Inyecta) for IgM, NS1 and IgG at the Instituto de Investigación Nutricional in Lima.

RESULTS

. The sensitivity of the rapid test was 68.0% for NS1 and IgM, and 86.0% for IgG, improving to 75.0% and 81.0% for NS1 and IgM, respectively, during the first three days. The specificity for all three analytes was greater than 87.0%. The concordance of the results, measured by the Kappa coefficient for the three analytes, was good and no cross-reaction with other arboviruses was found.

CONCLUSIONS

. The SD dengue DUO rapid test allows detection of NS1, IgM and IgG with adequate sensitivity and specificity. Sensitivity for IgM and NS1 increases when detected during the first three days of symptoms. Therefore, we recommend its implementation in primary care centers for early and timely diagnosis.

Dengue virus detection in Lao PDR and Colombia: Comparative evaluation of PCR tests

OBJECTIVES

Dengue virus (DENV) detection by polymerase chain reaction (PCR) facilitates diagnosis of dengue fever, which is the most frequent arboviral disease globally. Two studies were performed in countries with high dengue incidence, to assess the diagnostic performance of different PCR techniques.

METHODS/RESULTS

Two hundred and seventy-nine acute phase blood samples from febrile patients were analyzed for DENV by the RealStar Dengue RT-PCR kit (Altona Diagnostics) as gold standard in comparison with the Tropical Fever Core multiplex PCR (Fast Track Diagnostics). In total, 102 samples collected in Savannakhet Province (Lao PDR, Southeast Asia) in 2013 and 35 samples from Valledupar (Colombia, South America) tested positive for DENV by RealStar RT-PCR. In comparison, the Tropical Fever Core multiplex PCR detected 65.0% (65/102) and 68.6% (24/35) of these samples as positive for DENV in Savannakhet and Valledupar, respectively. Diagnostic sensitivity of the multiplex PCR strongly correlated with viral load. A subset of DENV PCR-confirmed samples was additionally tested by BNITM in house Dengue Type RT-PCR in comparison with two commercial test kits (RealStar Dengue Type RT-PCR [Altona Diagnostics], Dengue differentiation PCR [Fast Track Diagnostics]). The leading dengue serotype in Savannakhet was DENV-3 (58% [29/50]), while DENV-1 (53.8% [14/26]) was the predominant serotype found in samples collected in Valledupar by BNITM-type PCR. However, three DENV serotypes were circulating in Valledupar and in Savannakhet. In 2015, additional studies found predominantly DENV-4 (71% [12/17]) in Savannakhet.

CONCLUSIONS

Both studies emphasized that routine diagnostics in both regions will benefit from an expanded use of highly sensitive pan-dengue PCRs.

Evaluation of VIDAS® Diagnostic Assay Prototypes Detecting Dengue Virus NS1 Antigen and Anti-Dengue Virus IgM and IgG Antibodies

Dengue is a serious tropical disease caused by the mosquito-borne dengue virus (DENV). Performant, rapid, and easy-to-use assays are needed for the accurate diagnosis of acute DENV infection. We evaluated the performance of three prototype assays developed for the VIDAS^® automated platform to detect dengue NS1 antigen and anti-dengue IgM and IgG antibodies. Positive and negative agreement with competitor enzyme-linked immunosorbent assays (ELISA) and rapid diagnostic tests (RDT) was evaluated in 91 Lao patients (57 adults, 34 children) with acute DENV infection. The VIDAS^® NS1 assay showed the best overall agreement (95.6%) with the competitor NS1 ELISA. Both VIDAS^® NS1 and NS1 ELISA assays also demonstrated high sensitivity relative to DENV RNA RT-PCR set as gold standard (85.7% and 83.9%, respectively). In contrast, NS1 RDT was less sensitive relative to DENV RNA RT-PCR (72.7%). The overall agreement of VIDAS^® IgM and IgG assays with the competitor assays was moderate (72.5% for IgM ELISA, 76.9% for IgG ELISA, and 68.7% for IgM and IgG RDT). In most analyses, test agreements of the VIDAS^® assays were comparable in adults and children. Altogether, the VIDAS^® dengue prototypes performed very well and appear to be suitable for routine detection of dengue NS1 antigen and anti-dengue IgM/IgG antibodies.

Limited specificity of commercially available SARS-CoV-2 IgG ELISAs in serum samples of African origin

OBJECTIVES

Specific serological tests are mandatory for reliable SARS-CoV-2 diagnostics and seroprevalence studies. Here, we assess the specificities of four commercially available SARS-CoV-2 IgG ELISAs in serum/plasma panels originating from Africa, South America, and Europe.

METHODS

882 serum/plasma samples collected from symptom-free donors before the COVID-19 pandemic in three African countries (Ghana, Madagascar, Nigeria), Colombia, and Germany were analysed with three nucleocapsid-based ELISAs (Euroimmun Anti-SARS-CoV-2-NCP IgG, EDI™ Novel Coronavirus COVID-19 IgG, Mikrogen recomWell SARS-CoV-2 IgG), one spike/S1-based ELISA (Euroimmun Anti-SARS-CoV-2 IgG), and in-house common cold CoV ELISAs.

RESULTS

High specificity was confirmed for all SARS-CoV-2 IgG ELISAs for Madagascan (93.4-99.4%), Colombian (97.8-100.0%), and German (95.9-100.0%) samples. In contrast, specificity was much lower for the Ghanaian and Nigerian serum panels (Ghana: NCP-based assays 77.7-89.7%, spike/S1-based assay 94.3%; Nigeria: NCP-based assays 39.3-82.7%, spike/S1-based assay 90.7%). 15 of 600 African sera were concordantly classified as positive in both the NCP-based and the spike/S1-based Euroimmun ELISA, but did not inhibit spike/ACE2 binding in a surrogate virus neutralisation test. IgG antibodies elicited by previous infections with common cold CoVs were found in all sample panels, including those from Madagascar, Colombia, and Germany and thus do not inevitably hamper assay specificity. Nevertheless, high levels of IgG antibodies interacting with OC43 NCP were found in all 15 SARS-CoV-2 NCP/spike/S1 ELISA positive sera.

CONCLUSIONS

Depending on the chosen antigen and assay protocol, SARS-CoV-2 IgG ELISA specificity may be significantly reduced in certain populations probably due to interference of immune responses to endemic pathogens like other viruses or parasites.

A dengue type 2 reporter virus assay amenable to high-throughput screening

Dengue virus (DV) is an important mosquito-borne flavivirus threatening almost half of the world's population. Prophylaxis and potent anti-DV drugs are urgently needed. Here, we developed a high content imaging-based (HCI) assay with DV type 2 expressing the fluorescent protein mCherry (DV2/mCherry) to improve the efficiency and robustness of the drug discovery process. For the construction of the reporter virus, the mCherry gene followed by the ribosome-skipping 2A sequence of the Thosea asigna virus (T2A) was placed upstream of the full DV2 open reading frame. The biological characteristics including mCherry expression, virus replication rate, and plaque phenotype was examined and validated in BHK-21, Vero and C6/36 cells. A robust image-based antiviral assay combined with an automated robotic system was then developed, with a Z' factor of 0.73. To validate the image-based antiviral assay, a panel of reference compounds with different molecular mechanisms of anti-DV activity was assessed: (i) the glycosylation inhibitor, Celgosivir, (ii) two NS4b-targeting compounds: a 3-Acyl-indole derivative and NITD618, and (iii) two nucleoside viral polymerase inhibitors, 2'CMC and 7DMA. The inhibition profiles were quantified and obtained by means of HCI and RT-qPCR. Both methods resulted in very comparable inhibition profiles. In conclusion, a powerful and robust assay was developed with a fully automated data generation and processing pipeline. It makes the new reporter virus assay amenable to high-throughput screening of large libraries of small molecules.

Vector-borne diseases in pregnancy

Vector-borne infections cause a significant proportion of world-wide morbidity and mortality and many are increasing in incidence. This is due to a combination of factors, primarily environmental change, encroachment of human habitats from urban to peri-urban areas and rural to previously uninhabited areas, persistence of poverty, malnutrition and resource limitation in geographical areas where these diseases are endemic. Pregnant women represent the single largest ‘at risk’ group, due to immune-modulation and a unique physiological state. Many of these diseases have not benefitted from the same level of drug development as other infectious and medical domains, a factor attributing to the ‘neglected tropical disease’ title many vector-borne diseases hold. Pregnancy compounds this issue as data for safety and efficacy for many drugs is practically non-existent, precluding exposure in pregnancy to many first-line therapeutic agents for ‘fear of the unknown’ or overstated adverse pregnancy-foetal outcomes. In this review, major vector-borne diseases, their impact on pregnancy outcomes, current treatment, vaccination and short-comings of current medical practice for pregnant women will be discussed.

Potential antigenic cross-reactivity between SARS-CoV-2 and Dengue viruses

BACKGROUND

COVID-19 and dengue fever are difficult to distinguish given shared clinical and laboratory features. Failing to consider COVID-19 due to false-positive dengue serology can have serious implications. We aimed to assess this possible cross reactivity.

METHODS

We analyzed clinical data and serum samples from 55 individuals with SARS-CoV-2 infection. To assess dengue serology-status, we used dengue-specific antibodies by means of lateral-flow rapid test as well as enzyme-linked-immunosorbent-assay (ELISA). Additionally, we tested SARS-CoV-2 serology-status in patients with dengue and performed in-silico protein structural analysis to identify epitope similarities.

RESULTS

Using the dengue lateral-flow rapid test we detected 12 positive cases out of the 55 (21.8%) COVID-19 patients versus zero positive cases in a control group of 70 healthy individuals (P= 2.5E-5). This includes nine cases of positive IgM, two cases of positive IgG and one case of positive IgM as well as IgG antibodies. ELISA testing for dengue was positive in two additional subjects using envelope-protein directed antibodies. Out of 95 samples obtained from patients diagnosed with dengue before September 2019, SARS-CoV-2 serology targeting the S protein was positive/equivocal in 21 (22%) (sixteen IgA, five IgG) versus four positives/equivocal in 102 controls (4%) (P= 1.6E-4). Subsequent in-silico analysis revealed possible similarities between SARS-CoV-2 epitopes in the HR2-domain of the spike-protein and the dengue envelope-protein.

CONCLUSIONS

Our findings support possible cross-reactivity between dengue virus and SARS-CoV-2, which can lead to false-positive dengue serology among COVID-19 patients and vice versa. This can have serious consequences for both patient care and public health.