Dengue (RNA Qualitative RT-PCR):
Why Dengue (RNA Qualitative) RT-PCR Test?
CLINICAL INFORMATION
Dengue fever is a mosquito-borne tropical (Arthropod-Borne Disease) disease caused by dengue fever virus (DENV – is a RNA virus, belongs to Flaviviridae, genus: Flavivirus). There are four dengue virus serotypes namely: DENV-1, DENV-2, DENV-3 AND DENV-4. Dengue is spread by the vector female mosquitoes. Aedes aegypti is the cause of dengue fever. High incidence prevails when a person travels (travel history) from endemic areas of the dengue virus. The infected mosquito vector with the dengue virus acts as a reservoir in the mosquito’s salivary gland. During a blood meal, the transmission of the virus occurs through the proboscis of an infected mosquito and thus enters systemic circulation in humans (host). The dengue virus enters the WBCs to replicate and later accumulates in the liver and bone marrow. Common clinical signs and symptoms are (due to the signalling of WBCs like cytokines and interferons) headaches, chills, rigors, intermittent high fever (its nature is the biphasic or saddleback type where fever appears and recedes /self-limiting), vomiting, muscle, pain behind the eyes, joint pain (break-bone fever) along with skin rashes (petechiae/maculopapular or vasculitic type) and hallmark of this infection is low platelets (results because of bone marrow dysfunction due to infection of the stromal cells), capillary permeability (fluid from blood vessels permeates into body cavities hence low blood volume fails to supply blood to vital organs for its function) results in a mild bleeding eg. Nose bleed, bleeding gums or easy bruising. It can either develop into Dengue Hemorrhagic Fever- DHF (It reduces the blood platelets and hence results in bleeding and leakage of blood plasma) or Dengue Shock Syndrome – DSS (blood pressure drastically reduces to dangerously low levels). Finally as this stage advances, its progression to fluid overload affects the brain leading to reduced levels of consciousness and/or results in seizures. It can lead to complications like lymph node swelling, liver enlargement, inflammation of the brain and can cause its associated neurological disorders like transverse myelitis, Guillan- Barre syndrome, impairment of vital organs like liver, heart etc. In chronic stages, as this condition progresses, it results in massive complications such as failure of the circulatory system leading to massive bleeding, shock and death. Symptoms of late complications include rapid breathing and/or difficulty in breathing (shortness of breath), fatigue, irritability or restlessness, severe stomach pain, persistent vomiting, bleeding from nose & gums, blood in urine, stool and vomit. In pregnant women (vertical transmission is also reported from mother to child in the fetus) it can result in miscarriages, low birth weight, fetal distress, premature birth etc.PCR – Polymerase Chain Reaction (PCR) technology (involves 3 main stages, denaturation, annealing and elongation), is a very sensitive methodology used in medicine as well as research purposes for elucidating DNA sequencing. This test involves extraction of genetic material by isolation and amplifies the genetic material (DNA Cloningby PCR technique) present in the sample specimen to many folds by replication. Thus the amplified sample specimen detects and reads the signal and test results are interpreted as positive or negative. Therefore PCR application in genetic testing is performed to detect pathogenic or altered or mutated DNA (i.e error in a specific part of DNA). RT-PCR: Reverse Transcriptase PCR or RT-PCR allows the use of RNA as a template (since some viruses contain only single-stranded RNA instead of DNA). An additional step allows the use of RNA as a template (RNA is transcribed using the enzyme RNA Polymerase into its complementary DNA – cDNA, which is RNA-DNA hybrid), which is then amplified, detected and quantified for test results. Hence enterovirus quantitative RT-PCR Test is performed. Dengue RT-PCR Test – This test is considered the gold standard for testing Dengue. The PCR Testing is NAAT testing or that test that tests the nucleic acid of the virus itself and are more sensitive and effective tests (This is more efficient than IgM or IgG antibody test since there is a possibility for cross-reactivity eg. Chikungunya, yellow fever, encephalitis etc. Additional tests include NS1 antigen detection by ELISA, IgG and IgM dengue antibody tests, combined testing with a nucleic acid amplification test - NAAT. Other tests include PRNT- Plaque Reduction Neutralization Test to detect neutralizing antibodies against dengue virus.
General Instructions:
Sample Requirement: Specimen - Blood sample collected from the vein. Test Preparation: None.
NOTE - Sample for specimen collections may vary based on the patient’s condition/cases according to the patient’s presenting complaints/signs or symptoms:
SPECIMEN REQUIREMENT (Special or Rare Cases) - As instructed and guided by Physician / Clinician / Pathologist / as per Laboratory’s requirements, according to procedures and protocols.
This Multi-Specialty Clinical Referral Laboratory RTDIAGNOSTICS provides precise and accurate tests with an extensive range of testing services to the medical centres to help in the diagnosis and identification of pathology in the test specimens for infectious diseases and also to evaluate the function of organ systems of the patient. It prevents further complications and helps to stabilize and restore health to near normalcy at the earliest without delay.
