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Institute
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.
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.