Dengue Virus (serotypes 1 to 4) – IgM and IgG antibodies; Molecular diagnosis (RT-PCR); Serotypes identification (RT-PCR and sequencing)
Information 02-01-2013.
This virus is expanding to countries where it has not previously been seen, and now it has been considered the most important Arbovirus that affects people. This virus is included in the group of viruses transmitted by arthropods (Arbovirus: Athropod Borne Virus), being transmitted mainly by Aedes aegypti and Aedes albopictus. It belongs to the Flavivirus genus of the Flaviviridae family, with other viruses such as West Nile virus, the Yellow Fever virus, the Japanese Encephalitis virus, or the virus of the St. Louis's encephalitis.
This disease is considered a foreign problem, which affects persons who lives in endemic areas, or who traveled to them, but has been diagnosed in two indigenous cases in Nice (France) in 2010. Its extension is due to the climatic changes that have allowed an expansion of their arthropod vectors, the expansion of Aedes aegypti in urban environments, the global expansion of Aedes albopictus and the increase of intercontinental trips. Currently, we have extended almost all tropical and subtropical zones, affecting more than 100 countries in Africa, America, Eastern Mediterranean, Asia and the Western Pacific.
In general, this disease is characterized by a mild fever disease (Classic Dengue fever), that can progress to a more severe disease as the Dengue Hemorrhagic fever (DHF) and the Dengue Shock Syndrome (DSS).
For diagnosis there are several possibilities: 1) Isolation of the virus; 2) Antigen detection; 3) Antibodies detection; and 4) Amplification of viral RNA.
Of these, isolation in culture is possible, and is the "Golden Standard", but it requires time and we can do it in IVAMI because we have facilities with cellular systems, and biosafety facilities; but not in other laboratories that lack these facilities.
Antigen detection has been provided to detect NS1 non-structural protein (DENV NS1) in serum and postmortem necropsy samples from non-fixed tissues. But it is useful in the initial stage of infection, although it is not very sensitive and is inhibited by the presence of the response that sequesters the antigen, such as those that exist in secondary responses. Therefore, it is not a recommended option, and we do not perform it in IVAMI,
The detection of antibodies by serological methods requires the samples of acute phase and convalescence phase, in order to detect seroconversion. Instead, we can perform the detection of IgM antibodies when a single sample is available. We can perform in IVAMI, but does not allow to differentiate the serotypes.
The amplification of viral RNA by RT-PCR is a method that obviates the disadvantages indicated for the other procedures, since it is a rapid, sensitive method that can be performed with serum and tissues, and even with fixed and included in paraffin tissues. At the same time, the presence of viruses when amplifying the NS5 genomic region and/or the C gene, allows also, differentiate by group or serotype-specific amplifications, each of the four dengue serotypes (DENV 1 , 2, 3 or 4).
Tests carried out in IVAMI:
- IgG and IgM antibodies.
- Molecular diagnosis (RT-PCR).
- Typing to identify any of the 4 serotypes (DENV-1, 2, 3 or 4).
Recommended sample:
- Whole blood, drawn with EDTA (2 mL).
- Serum or plasma (of blood drawn with EDTA).
Conservation and shipment of the sample:
- Refrigerated (preferred) for less than 2 days.
- Frozen: more than 2 days.
Delivery of results:
- Molecular diagnosis (RT-PCR): 24 to 48 hours.
Cost of the test:
- Molecular diagnosis (RT-PCR), without typing: Consult ivami@ivami.com.
- Molecular diagnosis (RT-PCR), including typing if positive (RT-PCR and sequencing): Consult ivami@ivami.com.