Article: Dr med Hagen Frickmann
Dengue Fever: Diagnosis of Dengue Fever Infection
In the acute phase of the disease, during which the patient usually presents to the doctor, the main focus is on the direct detection of the pathogen. Rapid tests are particularly suitable here, especially during deployments
3. Diagnosis of Dengue Fever Infection
In the acute phase of the disease, during which the patient usually presents to the doctor, the main focus is on the direct detection of the pathogen. Rapid tests are particularly suitable here, especially during deployments. The performance statistics of these rapid tests vary depending on the test. In a recent review, fluctuations in the sensitivity of the rapid tests used to detect the dengue virus NS1 antigen of between 38% and 71% were found, with a specificity of between 76% and 80% [Hunsperger et al., 2014]. If the NS1 rapid test is combined with serological tests for IgG and IgM antibodies, this is able to significantly increase the sensitivity [Kassim et al., 2011] – in one study up to more than 90% [Fry et al., 2011]. In contrast, the sensitivity with dengue virus IgM rapid tests when used alone is stated as being only 30-96% with a specificity of 86% to 92%. [Hunsperger et al., 2014].
If the necessary infrastructure requirements are available in the deployment area, the NAT-based (nucleic acid amplification testing) direct detection of dengue viruses can also be considered, for which – in addition to in-house systems available to various nations – there are a number of commercially available PCR systems available for the acute diagnosis of dengue infection [Levi et al., 2007; Najioullah et al., 2014; Saengsawang et al., 2014; Tsai et al., 2016]. Corresponding real-time PCR systems are offered either as simplex PCRs, e.g. the RealStar® Dengue RT-PCR Kit (altona Diagnostics, Hamburg, Germany) or the LightMix® Modular Dengue Virus (TIB MOLBIOL, Berlin, Germany), as well as in defined multiplex PCR panels for the diagnosis of fever after a stay in the tropics, e.g. in the "FTD Tropical Fever Core" panel (Fast-track diagnostics Ltd., Sliema, Malta).
Fully automatic multiplex PCR systems which can also be used by personnel with few qualifications are also suitable for the diagnosis of dengue fever in tropical deployment areas. For example, the firm analyticon instruments gmbh (Rosbach von der Höhe, Germany) recently held out the prospect of the impending market launch of a "Tropical Fever Panel" for a fully automatic FilmArray PCR system which also includes malaria, leptospirosis, chikungunya, anthrax, plague, tularaemia, ebola, Marburg, Crimean Congo haemorrhagic fever (CCHF), Lassa, typhus, visceral leishmaniasis, West Nile fever and Zika (personal communication with a company representative). Such fully automatic bench-top systems, which to all intents and purposes have the character of a rapid test due to their ease of use and the fast provision of the results, can provide valuable services in the field laboratory.
The interpretation of serological diagnostics is challenging due to the broad serological cross-reactions within the flaviviruses [Peeling et al., 2010]. However, the diagnostic gold standard for the clarification of complex serological constellations remains the plaque reduction neutralisation test [Maeda & Maeda, 2013] which – as a technically very complex procedure – is reserved for specialised centres in the home country and does not therefore typically represent a diagnostic option for the field laboratory.
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Dr med Hagen Frickmann